Testing and Adjusting

Usage:

Troubleshooting

Introduction

On the pages that follow is a list of possible problems. Several common problems are covered but these problems are not arranged in any particular sequence.

Before checking the list of problems, check the SCM display for any diagnostic codes that may be shown. These codes will aid in finding the problem (see Diagnostic Code Interpretation).

Identify your particular type of problem from the Problem List, then go directly to that problem. However, when you begin the procedure for that problem, start at Step 1 and follow through the step by step procedure. The steps in a particular problem provide a definite sequence to be followed for a logical, one by one elimination of many variables. These steps are arranged in order from the more probable/easiest to check, to the less probable/more complex to check.

When the cause of the problem is found and corrected, stop the test. Do not continue through the complete procedure just because it is there.

Test Instruments

Caterpillar Digital Multimeter (6V7070) - can be used for many of the voltage and resistance checks. Rectifiers can also be checked with the special diode function. For further information on using the digital multimeter, see Special Instruction, Form SEHS7734.

Diagnostic Code Interpretation

Diagnostic codes are displayed on the same display as the service hours, engine speed, battery voltage, engine oil pressure, and engine coolant temperature. When a diagnostic code is displayed, the arrow that indicates which of the above parameters are displayed will be missing and a flashing "dIAG" will be displayed. If several faults are present, the diagnostic codes will be displayed in sequence. The diagnostic code can be cleared from display by turning the Engine Control Switch (ECS) to the reset position. Before attempting a repair, move the ECS to the reset position and restart engine to see if problem recurs.

NOTE: See the Problem List for display codes.

Troubleshooting Problem List

1. SCM Display = 01 dIAG, no magnetic speed pickup (speed sensor) signal.

2. SCM Display = 02 dIAG, no oil pressure/temperature sensor (transducer) signal.

3. SCM Display = 03 dIAG, a problem with inputs from the ECS.

4. SCM Display = 04 dIAG, loss of setpoints programmed into the SCM memory.

5. SCM Display = 05 dIAG, engine shutdown with no shutdown command from the SCM.

6. SCM Display = 06 dIAG, internal failure of SCM or unstable voltage supply.

7. SCM Display = 07 dIAG, internal SCM programming switch does not match program.

8. SCM Display = 08 dIAG, temperature probe problem.

9. Engine cranks but does not start or shuts down immediately after starting.

10. Engine does not crank (if equipped with an electric starter).

11. Starter remains engaged or continues to run after engine has started (If equipped with an electric starter).

12. Engine shutdown occurs, all six LED fault indicators on the SCM flash.

13. LED fault indicator on the SCM will not reset.

14. Engine shutdown occurs, overcrank LED is lit.

15. Engine shutdown occurs, overspeed LED is lit.

16. Engine shutdown occurs, low oil pressure LED is lit.

17. Engine shutdown occurs, high coolant temperature LED is lit.

18. Engine shutdown occurs, emergency stop LED is lit.

19. Engine shutdown occurs, auxillary LED is lit.

20. No engine shutdown when a fault occurs.

21. Engine shutdown with no LED's lit or diagnostic codes on SCM.

22. Remote annunciator or control panel alarm module, data link controlled LED's all flash at a rate of once per two seconds (.5 Hz).

Problem 1: SCM Display = 01 dIAG, no magnetic speed pickup (speed sensor) signal.

Step 1.

Test Procedure:

Disconnect speed sensor leads (not ground wires) from terminals 1 and 7 on the SCM and measure resistance with a multimeter. Also measure resistance between speed sensor leads and ground.

Probable Cause:

1. Resistance between speed sensor leads is between 400 and 520 ohms. Lead to grond resistance is above 5000 ohms.

Speed sensor wiring is okay. Go to Step 2.

2. Resistance is below 400 ohms.

Short circuit in wiring or sensor. Repair wiring or replace speed sensor as needed.

3. Resistance is above 520 ohms.

Wire is broken or connector is defective. Repair broken wire or bad connection or replace speed sensor as needed.

4. Resistance between sensor leads and ground is below 5000 ohms.

Speed sensor is grounded. Repair wiring harness or replace speed sensor as needed.

Step 2.

Test Procedure:

Reconnect speed sensor leads to terminals 1 and 7 on the SCM. Use a 6V7070 Multimeter (or a meter of known accuracy) to measure AC voltage across terminals 1 and 7 on the SCM while cranking the engine. Be sure that you can reach 250 rpm.

Probable Cause:

1. Speed sensor voltage is 1.0 volt AC or greater.

Attempt to start. If 01 dIAG reappears, replace speed sensor. If 01 dIAG still appears, replace SCM.

2. Speed sensor voltage is below 1.0 volt AC.

Adjust speed sensor gap (see Service Procedure D). If speed sensor voltage is still low, replace speed sensor.

Problem 2: SCM Display = 01 dIAG, no oil pressure/temperature sensor (transducer) signal.

Step 1.

Test Procedure:

Measure the voltage between terminal 4 and battery negative of the SCM. Disconnect the 3 pin connector at the pressure/temperature sensor (transducer) and measure the voltage between terminal 4 and battery negative. Disconnect the wire from terminal 4 and measure the voltage between terminal 4 of the SCM and battery negative.

Probable Cause:

1. Voltage is between 11 and 15 VDC in all cases.

Power supply is okay. Go to Step 2.

2. Voltage is above 20 VDC in all cases.

Replace SCM. It is likely that pressure/temperature transducer has also been damaged.

3. Voltage is above 15 VDC but below 20 VDC in all cases or below 11 VDC in all cases.

Replace SCM.

4. Voltage goes from below 11 VDC to between 11 and 15 VDC when the 3 pin connector is disconnected.

Replace pressure/temperature transducer.

5. Voltage goes from below 11 VDC to between 11 and 15 VDC when wire to terminal 4 is disconnected.

Repair grounded wiring between SCM and pressure/temperature transducer.

6. Voltage is above 15 VDC initially but is between 11 and 15 VDC when wire to terminal 4 is disconnected.

Repair wiring between SCM and pressure/temperature transducer. Wire may be shorted to +24 volts. If so, pressure/temperature transducer will probably fail and should be replaced.

Step 2.

Test Procedure:

Reconnect any wires that were disconnected in Step 1. Measure the voltage on terminal 5 of the SCM with respect to battery negative. Use the 6V7070 Digital Multimeter or equivalent meter.

Probable Cause:

1. Voltage is 4 to 8 VDC.

Go to Step 3.

2. Voltage is above 8 VDC.

2. Wire from terminal 5 of SCM to pressure/temperature transducer (sensor) is open or high resistance. Repair as required.

3. Voltage is below 4 VDC.

Recheck supply voltage to the pressure/temperature sensor (Step 1). If okay, disconnect wire to terminal 5 of SCM. If voltage now goes above 8 VDC, replace the pressure/temperature transducer (sensor). If voltage remains low, replace the SCM.

Step 3.

Test Procedure:

Disconnect the 3 pin connector at the pressure/temperature transducer and measure voltage between battery negative and pin 1 of the wiring harness connector. Also measure resistance between battery negative and pin 2 of this connector.

NOTE: In an emergency situation, it is possible to operate with no oil pressure or coolant temperature protection by reprogramming the SCM (see Service Procedure A). Oil pressure and coolant temperature gages should be installed to give operator an indication of engine conditions. If this is done, be sure to reprogram when the pressure/temperature transducer is replaced.

If the SCM is programmed to operate with no oil pressure and water temperature protection and the 02 dIAG cannot be reset, the SCM is defective. Check for loose connections or low battery voltage before replacing SCM.

Probable Cause:

1. Voltage is between 11 and 15 VDC and resistance is below 1 ohm.

Supply to pressure/temperature transducer okay. Replace pressure/temperature transducer.

2. Voltage is below 11 VDC.

Repair wiring between SCM and pressure/temperature transducer.

3. Resistance is above 5 ohms.

Repair wiring between SCM and battery negative.

Problem 3: SCM Display = 03 dIAG, a problem with inputs from the ECS.

Test Procedure:

The Engine Control Switch (ECS) must connect SCM terminal 9 or 10 or 11 or 12 to battery negative. If both 9 and 11 are connected to negative, there will be an auto start. Any wiring error or loose connection will cause the 03 diagnostic code. Check ECS and wiring from ECS to SCM, repair as needed.

Probable Cause:

1. Wiring and ECS check okay.

Replace the SCM.

2. Wiring or ECS check bad.

Repair or replace components as necessary.

Problem 4: SCM Display = 04 dIAG, loss of setpoints programmed into the SCM memory.

Test Procedure:

Reprogram the SCM (see Service Procedure A) and turn the ECS to reset.

Probable Cause:

1. 04 dIAG does not recur.

Problem solved.

2. 04 dIAG recurs.

Replace SCM.

Problem 5: SCM Display = 05 dIAG, engine shutdown with no shutdown command from the SCM.

Step 1

Test Procedure:

Crank the engine by moving the ECS to manual position and observe the action of the governor and carburetor throttle. If engine will not crank, troubleshoot starting system according to troubleshooting procedure under Problem 10.

If a 2301 Electric Governor is used, measure the voltage supplied to the governor.

NOTE: See Service Procedure A on how to identify Energize To Run (ETR) or Energize To Shutdown (ETS) system.

Probable Cause:

1. Carburetor throttle and governor moves in Fuel On direction.

The problem is in the engine ignition or fuel system. Refer to engine portion of the Service Manual.

2. 2301 Electric Governor is used and supply voltage is found to be greater than 15 volts.

Problem is in governor or actuator system. Refer to 2301 Electric Governor Service Manual, Form SENR2928.

3. 2301 Electric Governor is used and the supply voltage is found to be less than 15 volts.

Problem is in wiring to the 2301 Electric Governor. Go to Step 3.

Step 2

Test Procedure:

Connect a jumper between terminals S and 23 of the terminal strips on the back of the SCM and crank the engine. Be prepared to use manual shutoff if needed.

Probable Cause:

1. Engine starts and runs.

The Fuel Control Relay (FCR) was not energizing the gas shutoff valve (GSOV). Check FCR (see Service Procedure B).

2. Engine does not start.

The gas shutoff valve is defective or stuck, or solenoid is not correct, or the carburetor throttle is stuck in the shutoff position. If there is no voltage at terminal S, fuse F6 may be open and should be replaced. Find the source of the problem and correct.

Step 3 (2301 Governor only)

Test Procedure:

Crank the engine and measure the DC voltage between the following points and battery negative: the battery positive terminal on the preregulator (located under 2301 in control panel), terminal 1 of the F9 fuse if preregulator is not used, terminal 20 on the SCM, terminal M on the SCM and terminal L on the SCM.

Probable Cause:

1. Voltage is below 15 VDC at all of these points.

Battery voltage is low or wiring from battery to control panel is defective. Charge battery or repair wiring as needed.

2. Voltage is above 15 VDC on terminal L of SCM only. Voltage is low at all other points.

Fuse F4 is blown. Replace fuse.

3. Voltage is above 15 VDC on terminals M and L of the SCM. Voltage is low at all other points.

Run Relay contact is not closing. Check the SCM for diagnostic codes before checking the relay. (See Procedure B.)

4. Voltage is above 15 VDC on terminals M and L and 20 of the SCM. Voltage is low at all other points.

Check the wiring between terminal 20 of the SCM and the battery positive terminal on the preregulator or F9 fuse if preregulator is not used. Repair as needed.

5. All voltages are above 15 VDC. The voltage at the 2301 remains low.

The preregulator fuse or the F9 fuse or the preregulator or wiring is defective. Repair as needed.

Step 4

Test Procedure:

Check for another diagnostic code. If none is displayed, remove fuse F7 (between terminals T and U) from back of SCM.

Probable Cause:

1. Ignition system shutoff does not trip and engine starts.

The Magneto Grounding Relay (MGR) is de-energizing the ignition system. Check resistance between terminals U and 24 on the SCM. If it is above 5 ohms, go to Procedure B. If not, look for wiring errors that might interrupt voltage to the ignition system.

2. Ignition system shutoff continues to trip.

The ignition system shutoff is defective. See Engine Service Manual section on the ignition system.

Problem 6: SMC Display = 06 dlAG, internal failure of SCM or unstable voltage supply.

Test Procedure:

Reset and wait 90 seconds. Restart to see if problem re-occurs. If it does, look for possible sources of electrical noise such as loose connections in supply to SCM. Install jumper between terminals D and F of the SCM. Reset and start engine.

Probable Cause:

1. 06 dlAG recurs only when engine is running.

Loose connection between battery + or - to SCM is still likely. Run separate supply wires. Replace SCM if this fails to correct problem.

2. 06 dlAG recurs when engine is not running.

Loose connection still possible but less likely. Replace SCM unless an external electrical noise source can be identified.

3. 06 dlAG does not recur.

Check Crank Termination Relay (CTR) or Fuel Control Relay (FCR) contacts or leave jumper connected if battery drain is not a problem.

4. 06 dlAG reoccurs when engine is starting and engine cranks slowly or not at all.

Battery voltage is low. Charge and/or replace batteries.

Problem 7: SCM Display = 07 dlAG, internal SCM programming switch does not match program.

Test Procedure:

The 07 dlAG code simply indicates that the setpoint value programmed into setpoint 02 does not match the position of the rotary switch. (See Procedure A).

Problem 8: SCM Display = 08 dlAG, temperature probe problem.

Test Procedure:

Check connectors between oil pressure/temperature transducer (sensor) and the temperature probe before going to Service Procedure E.

Problem 9: Engine cranks but does not start or shuts down immediately after starting.

Test Procedure:

Look at the SCM Display.

Probable Cause:

1. Overcrank LED's is lit (is on).

Reset control and check cycle crank time and overcrank time setpoints (see Service Procedure A). Both times should be 5 seconds or more. If engine will not start in 5 seconds, troubleshoot engine/fuel system/governor.

2. Overcrank LED did not light (if off). If the engine started and then shut down an 05 diagnostic code should be displayed.

Go to Problem 5, diagnostic code 05, regardless if 05 is displayed or not.

3. Some other diagnostic code is displayed.

Go to Problem List and do problem indicated by the diagnostic code.

Problem 10: Engine does not crank (If equipped with an electric starter).

Step 1.

Test Procedure:

Look at SCM Display.

Probable Cause:

1. All 6 LED fault indicators are on.

Go to Problem 12, all six LED fault indicators are on.

2. One or more but not all of the 6 LED fault indicators are flashing.

There is a shutdown fault. Go to Problem List and the problem indicated by fault.

3. A diagnostic code is displayed.

Go to Problem List and do problem indicated by the diagnostic code.

4. No LED fault indicators are lit and no diagnostic code is displayed.

Defect is in the starting circuit. Allow five minutes for CB2 in control panel to cooldown and automatically reset. Attempt to start the engine. If engine will not crank go to Step 2.

Step 2.

Test Procedure:

Look at the battery voltage displayed on the SCM Display.

Probable Cause:

1. Voltage is low (1 to 20 volts).

Charge the battery or repair loose connections between battery cable terminal and battery.

2. Voltage is above 20 volts.

Go to Step 3.

Step 3.

Test Procedure:

Prepare for the engine to crank. Momentarily connect a wire between terminals 1 and 5 on the generator mounted terminal strip (TS1).

Probable Cause:

1. Engine cranks.

Go to Step 4.

2. Engine does not crank.

Check to see if terminals 4 and 5 on TS1 are jumpered together. If so, the magnetic switch or the pinion solenoid or the starter motor is defective. Repair or replace as required.

Step 4.

Test Procedure:

Attempt to start engine (ECS in manual) and measure voltage between SCM terminal 25 and battery negative, terminal W and battery negative, battery positive and battery negative.

Probable Cause:

1. All voltages are below 20 VDC.

Battery or wiring to SCM is defective. Repair or replace defective parts.

2. Only the voltage on terminal 25 is below 20 VDC.

Check the Starter Motor Relay (SMR) (see procedure B).

3. The voltage on terminals 25 and W are below 20 VDC. The battery position is above 20 VDC.

Replace fuse F8. Also check wiring from terminal W to battery positive.

Problem 11: Starter remains engaged or continues to run after engine has started (If equipped with an electric starter).

Step 1.

Test Procedure:

Check for diagnostic codes on the SCM display and go to that respective problem. If no diagnostic codes are shown, shut the engine down and check the voltage between terminals 5 and 2 (5 is positive) on the generator terminal strip (TS1).

Probable Cause:

1. Engine continues to crank and 15 VDC or more is measured.

Go to Step 2.

2. Engine no longer cranks.

Check crank terminate setpoint (see Service Procedure A, Engine Setpoint Chart). If setpoint is okay, go to Problem 1 under 01 dlAG. If speed sensor signal is good and shielded wire is in good condition, replace the SCM.

3. Engine continues to crank and there is less than 1 VDC between terminals 5 and 2.

Problem is in magnetic switch or in starter or pinion solenoid. Repair as required.

Step 2.

Test Procedure:

Disconnect wire No. 5 on the generator terminal strip TS1.

Probable Cause:

1. Engine no longer cranks. Voltage between terminals 5 and 2 on generator terminal strip is still above 15 VDC.

Check resistance between terminals W and 25 on SCM. If it is below 5 ohms, go to Service Procedure B. If not, check for shorts or incorrect wiring that supplies voltage to terminal (5).

2. Engine continues to crank.

Problem is in magnetic switch or in starter or pinion solenoid. Repair as required.

Problem 12: Engine shutdown occurs, and/or all six LED fault indicators on the SCM are on.

Test Procedure:

Be sure that terminal 8 on the SCM is not grounded.

Probable Cause:

1. Fault LED's do not turn on.

Terminal 8 on the SCM is grounded. Correct the problem.

Problem 13: LED fault indicator on the SCM will not reset.

Test Procedure:

Move the Engine Control Switch (ECS) to the reset position. If the LED does not go out, connect a jumper wire between terminal 12 on the SCM and battery negative. Disconnect jumper wire.

Probable Cause:

1. LED resets (goes out) when jumper wire is connected.

Problem is in ECS or wiring to the ECS. Repair as required.

2. LED does not reset (still lit).

Be sure that the fault condition no longer exists. (Example: Engine high coolant temperature LED is lit and engine is cool). If fault cannot be reset, replace the EMC.

Problem 14: Engine shutdown occurs, overcrank LED is lit.

Test Procedure:

Turn ECS to the reset position. If the overcrank LED does not go out, do Problem 13. If the LED goes out, go to Problem 9, "engine cranks but does not start" under test results A, Step 1.

Problem 15: Engine shutdown occurs, overspeed LED is lit.

Test Procedure:

Turn ECS to the reset position. If the overspeed LED does not go out, do Problem 13. If the LED goes out, check for possible causes of overspeed. If no causes are found, check the overspeed setpoint according to Service Procedure A. Attempt to start engine by moving the ECS to manual position.

Probable Cause:

1. Overspeed LED resets and engine starts and runs. Overspeed setpoint is correct.

Hold verify switch on back of the SCM in verify position and increase speed until shutdown occurs. If shutdown speed is 75% of overspeed setpoint, the overspeed function is okay. Look for governor or system problems. If shutdown speed is incorrect, go to Service Procedure D. Replace the SCM if no speed sensor problem is found.

2. Overspeed LED resets and engine starts, but overspeeds again.

If speed goes above overspeed setpoint, repair governor or system problem. If speed does not go high, go to Service Procedure D. Replace the SCM if no speed sensor problem is found.

3. Overspeed setpoint is below specifications.

Program is the correct setpoint according to Service Procedure A.

Problem 16: Engine shutdown occurs, low oil pressure LED is lit.

Test Procedure:

Turn ECS to the reset position. If the low oil pressure LED does not go out, do Problem 13. If the LED goes out check for possible causes of low oil pressure. If no causes are found, check the oil step speed and pressure settings that have been programmed into the SCM (see Service Procedure A).

Start the engine and check engine oil pressure at both low idle and high idle speed using the SCM display and a reliable oil pressure gauge. It may be necessary to program the SCM to operate without oil pressure protection. If the oil pressure is low, do not continue. Shut the engine down and repair the problem in engine lube system.

Probable Cause:

1. Engine oil pressure is below setpoints at low or high idle. See Identification section, character five for specific engine setpoints. Measurements by gauge and SCM display agree.

Problem is in engine. Refer to engine service manual.

2. One or more oil pressures are below the settings programmed into the SCM or oil step speed is set near low idle.

Check the pressure and speed specifications according to the model number identification fifth character. See Identification. If the SCM settings are incorrect, reprogram to correct the settings. If the SCM settings are correct, correct the engine problem. Refer to the engine service manual.

3. Engine oil pressure as measured with a gauge is at or above the SCM settings. Engine oil pressure as measured by SCM display is below the SCM settings.

Check the wiring and oil supply to the pressure/temperature transducer (sensor). If no problem can be found, replace the pressure/temperature transducer.

Problem 17: Engine shutdown occurs, high coolant temperature LED is lit.

Test Procedure:

Turn ECS to the reset position. If the high coolant temperature LED does not go out after engine is cool, do Problem 13. If the LED goes out check for possible causes for high coolant temperature. If no causes are found check the coolant temperature setting that has been programmed into the SCM (see Service Procedure A). It should be set for the specific engine model. See Identification section, character five for specific engine setpoints. Install an accurate coolant temperature gauge with the sensing bulb in area of high coolant flow, as close to temperature probe as possible. See note in Problem 16 under Test Procedures. Start the engine.

Probable Cause:

1. Coolant temperature setpoint is below proper shutdown setpoint.

Temperature setpoint is not correct. See Service Procedure A.

2. Temperature displayed by SCM and by gauge agree and is above the temperature setpoint. Setpoint is correct and high coolant temperature LED is still lit.

Engine is overheating. Troubleshoot cooling system.

3. Temperature displayed by SCM is 5°C (9°F) or higher than the temperature displayed by the gauge.

Check temperature probe (see Service Procedure E). If it is good, repeat test. Be sure of gauge accuracy. If SCM continues to read high, replace the pressure/temperature transducer (sensor).

4. Temperature displayed by SCM and by gauge agree and are below the temperature setpoint.

Go to Problem 13.

5. Temperature displayed on the SCM is the word "Hi" and the temperature on the gauge is below 98°C (208°F).

Check for shorts in wiring to the pressure/temperature transducer (sensor). Also check the temperature probe (see Procedure D).

Problem 18: Engine shutdown occurs, emergency stop LED's is lit.

Test Procedure:

Reset the emergency stop push button by turning until it pops out. Turn the ECS to "OFF/RESET" position. Disconnect the wire from terminal 14 on the SCM if LED remains on after attempting to reset.

Probable Cause:

1. Emergency stop LED goes out when wire is disconnected.

Emergency stop switch is stuck closed or grounded or wire is grounded. Repair as required.

2. Emergency stop LED remains on.

Move ECS to reset and back to manual position. If LED remains on, go to Problem 13.

Problem 19: Engine Shutdown occurs, auxillary LED is lit.

Test Procedure:

Turn the ECS to the reset position. If the reverse power LED does not go out, disconnect wire from terminal 13 on the SCM.

Probable Cause:

Reverse power LED goes out (resets) after resetting.

Problem was reverse power fault. Control panel is OK.

Reverse power LED goes out when wire is disconnected from terminal 13.

Reverse power relay will not reset. Check wiring and replace reverse power relay as required.

Reverse power LED remains lit.

Go to Problem 13.

Problem 20: No engine shutdown when a fault occurs.

Test Procedure:

Look at the SCM Display. If there is a diagnostic code displayed or a fault LED lit and the engine is not shut down, go to Step 1 (ETS) or Step 1A (ETR). If there is no diagnostic code or fault displayed, go to Step 2.

Step 1 (ETS).

Test Procedure:

Check the DC voltage relative to battery negative on TS1 terminal 7 in the generator and on terminals 23 and S and R on the SCM. The engine should be running with fault LED lit when checks are made.

Probable Cause:

1. All voltages are above 20 VDC.

The wire from terminal 7 in generator to solenoid is open or fuel shutoff solenoid is defective or not adjusted correctly. Repair as required.

2. Voltage at terminal 7 in generator is below 20 VDC. The other voltages are above 20 VDC.

The wire from terminal 7 in generator to terminal 23 in the SCM is open. Repair wire or connection.

3. Voltage of terminal 23 in SCM and terminal 7 in the generator is below 20 VDC. The other voltages are above 20 VDC.

The FCR relay may be stuck open. Go to Service Procedure B.

4. All voltages are below 20 VDC except for Terminal R on the SCM.

Replace Fuse F6. If problem continues solenoid may be shorted or wiring grounded. Repair as required.

5. All voltages are below 20 VDC.

Connection from battery positive to terminal R is defective. Repair as required.

Step 1A (ETR).

Test Procedure:

Remove fuse F6.

Probable Cause:

1. Engine shuts down.

Fuel Control Relay (FCR) contact is stuck closed. Check resistance between terminals S and 23 on SCM. If it is below 5 ohms, go to Service Procedure B. If not, look for wiring errors that might supply voltage to the Gas Shut-off Valve.

2. Engine continues to run.

Gas Shut-off Valve is stuck in run position. Shut engine down manually and troubleshoot solenoid and linkage.

Step 2.

Test Procedure:

Record all of the readings from the SCM display. Shut engine down and check the setpoint (see Service Procedure A) of the parameter that should be shutting engine down. If readings from the display are within allowed setpoints, there is no problem. If not, replace SCM.

Problem 21: Engine shutdown with no LED's lit or diagnostic codes on SCM.

Test Procedure:

Check to make sure SCM terminal 15 is not receiving a signal to shutdown (connect to battery negative B-).

Probable Cause:

1. Terminal 15 connected to battery negative (B-).

Problem is in wiring, find defect and repair or replace it.

2. Terminal 15 not connected to battery negative.

If no other defects can be found replace the SCM.

Problem 22: Remote annunciator or control panel alarm module, data link controlled LED's all flash at a rate of once per two seconds (.5 Hz).

Test Procedure:

Momentarily disconnect the battery or wire 1 at TS1-1 that is used to power the SCM. If the LED's stop flashing after the battery is reconnected, the problem is solved. If the LED's still flash, check to make sure serial data link wire 18 has good continuity from SCM terminal 6 to alarm module terminal 2.

Probable Cause:

No continuity of wire 18.

Repair or replace defective wire.

Wire 18 has continuity.

Replace ALM or remote annunciator or SCM.

Service Procedure A (Programming The SCM)

The set points programmed into the SCM are factory set. They can be changed to conform to the appropriate specifications when the SCM is moved from one engine type to another or when a special setting (usually overcrank or cycle crank) is needed. Install a security seal on the access cover to prevent unauthorized tampering. Do not open this cover in a humid environment and replace cover as soon as possible. A continuous bead of 6V6640 Sealant must be used to reseal this cover against humidity.

Programmability

Location Of Cover
(1) Cover.

Setpoint information is stored then used in the control strategy of the SCM. To program, shutdown the engine, remove access cover (1) on the backside of the SCM. A potentiometer (2) rotary switch (3) and momentary switch (4) will be visible. Note the position of the rotary switch (3). Turn rotary switch (3) to the position that corresponds to the setpoint to be adjusted. The LCD display will now read the position of the rotary switch and the data stored at that location. Press momentary switch (4). The data information corresponding to the position of the potentiometer will flash. Adjust potentiometer (2) to change the flashing data as desired. Once the data is correct, press momentary switch (4). The data information should stop flashing. Reprogramming of the setpoint is now complete. Return the rotary switch to position 0 if the system has an energize to run gas shutoff valve or position 1 if the system has an energize to stop gas shutoff valve. The engine will not run when in the program mode or if the position of the rotary switch does not correspond to the operating mode programmed into setpoint 02. Consult Caterpillar Inc. concerning alterations to setpoints that have been specified for your engine.

Component Location
(2) Potentiometer. (3) Rotary switch. (4) Momentary switch.

Setpoints

02 ETR/ETS: This setpoint value will describe the operating mode of the SCM.

0 or 2 programs the SCM to operate with an energize to run (ETR) gas shutoff valve.

1 or 3 programs the SCM to operate with an energize to shutdown (ETS) gas shutoff valve.

2 or 3 programs the SCM to ignore faults that could be caused by the transducer (sensor) module, i.e., high coolant temperature, low oil pressure and sensor module malfunction will not shut down the engine.

03 Metric/English: A setpoint value of 0 will command the SCM to display engine parameters in English. A setpoint value of 1 will display metric. See the chart that follows:

04 Ring Gear Teeth: This setpoint value must be same as the number of teeth on the ring gear. Range 95 to 350.

05 & 06 Overspeed: Program one of these positions to the desired engine speed at which an overspeed shutdown should occur. Position 05 has a range of 400 to 2950 rpm. Position 06 has a range of 2450 to 5000 rpm in increments of 10 rpm.

07 Crank Termination Speed: Once the engine speed passes this setpoint, the starter will no longer be energized. Range is 100 to 1000 rpm in increments of 10 rpm.

08 Oil Step Speed: Once the engine speed increases past this setpoint, the SCM will consider the engine to be above the low idle condition in regard to low oil pressure shutdown and alarm. Range is 400 to 1800 rpm in increments of 10 rpm.

09 Rated Oil Pressure Shutdown: If the engine lube pressure drops below the setpoint and the engine speed has been above the oil step speed for 9 seconds, the SCM will enter a low oil pressure shutdown condition. Range is 34 to 420 kPa (5 to 60 psi). Alarm signal sent to annunciator module occurs at 34 kPa (5 psi) above the shutdown.

10 Idle Oil Pressure Shutdown: If the engine lube pressure drops below this setpoint and the engine has been running for more than 9 seconds, the SCM will enter a low oil pressure shutdown condition. Range is 20 to 336 kPa (3 to 50 psi). The alarm signal sent to annunciator module occurs at 34 kPa (5 psi) above the shutdown.

11 High Coolant Temperature Shutdown: If the engine coolant temperature has been past the setpoint for 10 seconds. The SCM will enter a high coolant temperature shutdown condition. Range is 95 to 120°C (203 to 248°F). Alarm signal sent to annunciator module occurs at 6°C (11°F) below the shutdown temperature.

12 Low Coolant Temperature Alarm: If the engine coolant temperature has been below this setpoint for two seconds, the SCM will send an alarm signal to the annunciator module. Range is 10 to 30°C (50 to 86°F). Factory set at 21°C (70°F).

13 Overcrank Time: Total time to start the engine (from when first asked to start until overcrank is indicated). Range is 10 to 360 seconds. Factory setting is 360 seconds.

14 Cycle Crank: The amount of time the engine starter will crank. Also, the amount of time the starter will rest during a cycle crank. Range is 5 to 300 seconds. Factory setting is 300 seconds.

15 Cooldown: The amount of time the engine will run after it has been told to stop during a normal shutdown. Range is 0 to 30 minutes. Factory set at 0 minutes.

Service Procedure B (Relay Module)

The relay module is the housing that contains the fuses and terminals 16-27 and is part of the back of the SCM.

1. Disconnect wire from terminal 1 in generator. Check to be sure there is no voltage on the B+ terminal of the SCM. Some of the harness may need to be removed for easy accessibility. Since moisture can be introduced into the SCM when the relay housing is removed, it is important to do this in a fairly dry environment. Open this housing in an air conditioned area if relative humidity exceeds 60%.

Location Of Relay Housing
(1) Relay housing. (2) Screws.

2. Remove screws (2) and washers that hold relay housing (1) to main housing. To open housing, insert a thin knife blade between the relay housing and main housing. Drive it into the gap by tapping gently to break seal loose.

3. Open the housing and locate the relay or relays that need changed. Relays are labeled K1 through K7 on the PC board.

Relay Locations
(3) K7 - Fuel Control Relay (FCR). (4) K6 - Magneto Ground Relay (MGR). (5) K1 - 2301 Ramp (2301). (6) K5 - Run Relay (RR). (7) K2 - Fault Shutdown Relay (ENFR). (8) K4 - Starting Motor Relay (SMR). (9) K3 - Crank Termination Relay (CTR).

4. Remove the relay clip and pull the relay straight out.

5. Do Relay Performance Test:

Check continuity with ohmmeter as follows:

A. With no power on terminals 7 and 8, there should be 1 ohm or less between terminals 1 and 5. There should also be 1 ohm or less between terminals 2 and 6. Coil resistance between terminals 7 and 8 should be 140 to 180 ohms.

B. Apply 12 volts DC to terminals 7 and 8. There now should be 1 ohm or less between terminals 3 and 5. There also should be 1 ohm or less between terminals 4 and 6. There should be 100k ohm or more resistance between any other pairs of terminals.

6. Replace the relay if it fails this test and put the clip back on.

7. Check the connector going from the main housing to the relay PC board to assure that it is still inserted properly.

8. If replacing the relay does not fix problem or if the relay is not defective, replace the entire relay module.

9. Clean and apply primer (6V1541) to both housings' sealing surface.

10. Apply a continuous bead of sealant (6V6640) to the main housing sealing surface.

11. Install relay housing (1) on the main housing and fasten with original washers and screws (2).

12. Reconnect the wires that were removed.

Service Procedure C Alarm Module (DC Voltage Alarm Setpoint Adj.)

Location Of Plug
(1) Plug.

For all alarm applications, the low DC volts alarm setpoint is adjusted by means of a potentiometer located under an access plug (1) on the rear of the module. The adjustment range is 8 to 38 volts. To adjust the low DCV alarm setpoint:

1. Remove plug (1) which covers the adjustment pot on the rear of the annunciator module.

2. Disconnect wires on terminals 1 and 7. Connect a variable DC power supply to the annunciator module (+ voltage to terminal 1, -voltage to terminal 7). Set the power supply voltage to the desired low DCV alarm setpoint. (Must be between 8 and 38 volts.)

3. Turn the adjustment pot fully counterclockwise.

4. After one minute, the low DC volts LED will flash. Press the acknowledge/silence switch to get a steady low voltage light.

5. Turn the adjustment pot clockwise slowly until the LED goes out.

6. Replace the plug. Since moisture can be introduced into the ALM when the plug is removed, it is important to do this in a fairly dry environment. Remove this plug in an air conditioned area if relative humidity exceeds 60%.

7. Disconnect the variable DC power supply and connect wires removed in Step 2.

Service Procedure D (Speed Sensor Adj.)

Magnetic Pickup
(1) Clearance dimension. (2) Locknut.

1. Remove the magnetic pickup from the engine flywheel housing and turn the flywheel until a gear tooth is directly in the center of the threaded opening for the magnet pickup. Install the magnetic pickup again in the threads of the flywheel housing.

2. Turn (by hand) in a clockwise direction until the end of the magnetic pickup just makes contact with the gear tooth. Now turn the magnetic pickup back out 1/2 turn (180° in the counterclockwise direction) to get the correct air gap [clearance dimension (1)]. Now tighten locknut (2) to a torque of 45 ± 7 N·m (33 ± 5 lb ft).

NOTE: Do not let the magnetic pickup turn while locknut (2) is tightened.

Service Procedure E (Temperature Probe Resistance)

(1) Connector. (2) Transducer (sensor). (3) Temperature probe.

Measure the resistance of this probe (3) at room temperature using the 6V7070 multimeter. Disconnect connector (1). Be sure to make good connections to the probe connector pins. If the resistance does not agree with the following chart, check connector on temperature probe and repair any bad connections. If connector is okay, replace temperature probe (3).

If temperature probe resistance is okay, check connector from oil pressure/temperature transducer (sensor) to temperature probe. If connector is okay, replace oil pressure/temperature transducer (2).