STATUS CONTROL MODULE (SCM) Caterpillar

Undiagnosed problems are those problems which are indicated by incorrect operation or the fault LEDs on the SCM. Undiagnosed problems are NOT indicated on the LCD display of the SCM. When an undiagnosed problem occurs, see the Undiagnosed Problems List and perform the corresponding problem procedure.

Undiagnosed Problem List

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

11. Engine does not crank (if equipped with an electric starting motor).

12. Starting motor remains engaged or continues to run after engine has started (if equipped with an electric starting motor).

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

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

15. Engine shutdown occurs, overcrank LED is lit.

16. Engine shutdown occurs, overspeed LED is lit.

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

18. Engine shutdown occurs, high oil temperature LED is lit.

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

20. Engine shutdown occurs, auxiliary LED is lit.

21. No engine shutdown when a fault occurs.

22. Engine shut down with no LEDs lit or diagnostic codes on SCM.

23. Remote annunciator or remote control panel alarm module, data link controlled LEDs all flash at a rate of once per two seconds (0.5 Hz).

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

Step 1.

Test Procedure:

Disconnect speed sensor signal lead terminal 7 of the SCM. Measure resistance between the sensor lead and the SCM battery negative (ground) post with a multimeter.

Probable Cause:

1. Resistance between the lead and ground is between 100 and 270 ohms.

Speed sensor wiring is okay. Go to Step 2.

2. Resistance is below 100 ohms.

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

3. Resistance is above 270 ohms.

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

Step 2.

Test Procedure:

Reconnect speed sensor lead to terminal 7 on the SCM. Use a 6V7070 Multimeter (or a meter of known accuracy) to measure AC voltage across battery negative (ground) post and terminal 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 = 02 dlAG, no oil pressure/temperature module signal.

Step 1.

Test Procedure:

Measure the voltage between terminals 3 and 4 of the SCM. Disconnect the 3 pin sure seal connector (with the pink, black and orange wires) at the pressure/temperature module and measure the voltage between terminals 3 and 4 at the SCM. Disconnect the wire from terminal 4 and measure the voltage between terminals 3 and 4 of the SCM.

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 module is also 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 module.

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 module.

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 module. Wire may be shorted to +24 volts. If so, pressure/temperature module 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 terminal 3 of the SCM. Use the 6V7070 Digital Multimeter or equivalent meter.

Probable Cause:

1. Voltage is 4 to 8 VDC.

Voltage level is OK. Go to Step 3.

2. Voltage is above 8 VDC.

Go to Step 4.

3. Voltage is below 4 VDC.

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

Step 3.

Test Procedure:

Reconnect any wires that were disconnected in Step 2. Disconnect the 3 pin sure seal connector (with the pink, black and orange wires) at the pressure/temperature module. Measure the voltage between pins 1 and 2 of the wiring harness connector. Measure the resistance between pin 2 of the wiring harness and battery negative.

Probable Cause:

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

Supply wiring to pressure/temperature module is okay. Go to Step 5.

2. Voltage is below 11 VDC.

Repair wiring between SCM and the pressure/temperature module.

3. Resistance is above 5 ohms.

Repair wiring between pressure/temperature module and battery negative.

Step 4.

Test Procedure:

Reconnect any wires that were disconnected in Step 3. Disconnect the 3 pin sure seal connector (with the pink, black and orange wires) at the pressure/temperature module. Measure the voltage between pins 1 and 2 of the wiring harness connector and battery negative. Measure the voltage between pins 2 and 3 of the wiring harness connector. Measure the resistance between pin 2 of the wiring harness and battery negative.

Probable Cause:

1. Voltage at pin 1 is below 11 VDC or voltage at pin 3 is below 8 VDC.

Repair wiring between SCM and pressure/temperature module.

2. Resistance is above 5 ohms.

Repair wiring between pressure/temperature module and battery negative.

3. Voltage at pin 1 is between 11 and 15 VDC and voltage at pin 3 is above 8 VDC. Resistance is below 1 ohm.

Go to Step 5.

Step 5.

Test Procedure:

Reconnect any wires that were disconnected in Step 4. At the pressure/temperature module, disconnect the 3 pin connector (with the red, green and yellow wires) that goes to the engine oil pressure sensor. Measure the voltage between pin A (red power wire) and pin B (yellow ground wire) of the pressure/temperature module harness connector.

Probable Cause:

1. Voltage is less than 4.5 VDC.

Repair the wiring between pressure/temperature module and pressure sensor. If the wiring problem is NOT found, replace the pressure/temperature module.

2. Voltage is greater than 4.5 but less than 6.0 VDC.

Replace the engine oil pressure sensor which is located on the engine.

3. Voltage is greater than 6.0 VDC.

Replace the pressure/temperature module. It is likely that the pressure sensor is also damaged.

Problem 3: SCM Display = 03 dlAG, a problem with inputs from the MCS.

Test Procedure:

The Mode Control Switch (MCS) must connect SCM terminal 9, 10, 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 MCS and wiring from MCS to SCM, repair as needed.

Probable Cause:

1. Wiring and MCS check okay.

Replace the SCM.

2. Wiring or MCS check bad.

Repair or replace components as necessary.

Problem 4: SCM Display = 04 dlAG, loss of set points programmed into the SCM memory.

Test Procedure:

Reprogram the SCM (see Service Procedure A) and turn the MCS to OFF/RESET.

Probable Cause:

1. 04 dlAG does not recur.

Problem solved.

2. 04 dlAG recurs.

Replace SCM.

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

Step 1 (ETS or ETR System).

Test Procedure:

Crank the engine by moving the MCS to the START position and observe the action of the governor, the throttle and gas valve. If engine will not crank, troubleshoot starting system according to troubleshooting procedure under Problem 11.

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

Probable Cause:

1. Fuel valve moves in Fuel On direction.

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

2. The gas shutoff valve does NOT move.

Go to Step 2 (ETR).

Step 2 (ETR)

Test Procedure:

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

Probable Cause:

1. Engine starts and runs.

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

2. Engine does not start.

The gas shut-off valve (GSOV) is defective or stuck, or the solenoid is not correct. 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

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. Magneto system shutoff does not trip and engine starts.

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

2. Magneto system shutoff continues to trip.

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

Problem 6: SCM Display = 06 dIAG, 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 dIAG 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 dIAG 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 dIAG 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 dIAG 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 dIAG, internal SCM programming switch does not match program.

Test Procedure:

The 07 dIAG code simply indicates that the set point value programmed into set point 02 does not match the position of the rotary switch.

NOTE: After programming, it is possible for the 07 dIAG code to appear if the system is NOT reset.

Test Procedure:

Turn the MCS to the RESET position. Next, turn the MCS to the STOP position.

Probable Cause:

1. 07 dIAG code is NOT present.

There is not 07 dIAG code failure.

2. 07 dIAG code is still present.

The value of set point 02 does NOT match the rotary switch position. See Service Procedure A.

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

Test Procedure:

Check connectors between oil pressure/temperature module and the temperature probe before going to Service Procedure E.

Problem 9: SCM Display = 09 dIAG, oil pressure probe problem. SCM displays high oil pressure when the engine is NOT running and has cooled down.

Test Procedure:

Record the oil pressure the SCM is displaying. Disconnect the harness connector at the engine oil pressure sensor. Record the oil pressure the SCM is now displaying.

Probable Cause:

1. Both pressures displayed are above 965 kPa (140 psi).

In the wiring from the pressure/temperature module to the oil pressure sensor, check for a short between the green signal wire (pin C) and the red power wire (pin A).

2. The first displayed pressure is above 480 kPa (70 psi) but below 760 kPa (110 psi) and the second displayed pressure is 0 kPa (0 psi).

In the harness connector, check for an open ground circuit (pin B, yellow wire).

3. The first displayed pressure is 965 kPa (140 psi). The second displayed pressure is 0 kPa (0 psi).

Check the pressure sensor wiring and correct as needed. If no wiring problem is found, replace the engine oil pressure sensor.

4. Both pressures are above 0 kPa (0 psi) but below 965 kPa (140 psi).

Replace the pressure/temperature module.

Problem 10: Engine cranks but does not start or shuts down immediately after starting.

Test Procedure:

Look at the SCM Display.

Probable Cause:

1. Overcrank LED is lit (on).

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

2. Overcrank LED did not light (is 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 11: Engine does not crank (if equipped with an electric starting motor).

Step 1.

Test Procedure:

Look at SCM Display.

Probable Cause:

1. Display is completely blank, regardless of the Mode Control Switch (MCS) position.

Go to Step 2.

2. All six LED fault indicators are on.

Go to Problem 13, all six LED fault indicators are on.

3. One or more but not all of the six LED fault indicators are flashing.

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

4. A diagnostic code is displayed.

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

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

Defect is in the starting circuit.

Step 2.

Test Procedure:

Turn the Mode Control Switch (MCS) to STOP. Measure the voltage and check the polarity at terminals 1 and F of the SCM. With the positive meter lead on terminal F and the negative meter lead on terminal 1, measure the voltage.

Probable Cause:

1. Polarity is correct and voltage is between +15 and +45 VDC.

Replace the SCM.

2. Polarity is correct, but voltage level is below +15 VDC.

Check the battery voltage and check the wiring from the battery to the SCM. Replace or recharge the batteries or repair the wiring as required.

3. Polarity is NOT correct, voltage is negative.

Check and correct any improper connections between the battery and the SCM. Go to Step 3.

Step 3.

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 4.

Step 4.

Test Procedure:

Prepare for the engine to crank. Momentarily connect a wire between terminal 25 and positive battery on the SCM.

Probable Cause:

1. Engine cranks.

Go to Step 5.

2. Engine does not crank.

The pinion solenoid or the starting motor is defective. Repair or replace as required.

Step 5.

Test Procedure:

Attempt to start engine (MCS in START) 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 Starting Motor Relay (SMR) (see procedure B).

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

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

Problem 12: Starting motor remains engaged or continues to run after engine has started (if equipped with an electric starting motor).

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 25 and battery negative on the SCM.

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 set point (see Service Procedure A, Engine Set Point Chart). If set point is okay, go to Problem 1 under 01 dIAG. 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 25 and battery negative.

Problem is in starting motor or pinion solenoid. Repair as required.

Step 2.

Test Procedure:

Disconnect wire from terminal 25 of the SCM.

Probable Cause:

1. Engine no longer cranks. Voltage between terminal 25 and battery negative on SCM 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 25.

2. Engine continues to crank.

Problem is in starting motor or pinion solenoid. Repair as required.

Problem 13: Engine shutdown occurs, and/or all six LED fault indicators on the SCM are on.

Test Procedure:

Disconnect wires from terminal 8 on the SCM. Measure the DC voltage between battery positive and battery negative.

Probable Cause:

1. Fault LEDs do NOT turn on.

Wiring to terminal 8 on the SCM is grounded. Correct the problem.

2. Fault LEDs remain ON. Battery voltage is 15 VDC or less.

Battery voltage is low. Charge battery or correct wiring problem as required.

3. Fault LEDs remain ON. Battery voltage is above 15 VDC.

Replace the SCM.

Problem 14: LED fault indicator on the SCM will not reset.

Test Procedure:

Move the Mode Control Switch (MCS) to the OFF/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 MCS or wiring to the MCS. 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 SCM.

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

Test Procedure:

Turn the Mode Control Switch (MCS) to the OFF/RESET position. If the overcrank LED does NOT go out, go to Problem 14. If the LED goes out, go to Problem 10.

Problem 16: Engine shutdown occurs, overspeed LED is lit.

Test Procedure:

Turn the Mode Control Switch (MCS) to the OFF/RESET position. If the overspeed LED does NOT go out, go to Problem 14. If the LED goes out, check for possible causes of overspeed. If no causes are found, check the overspeed set point according to Service Procedure A. Attempt to start engine by moving the MCS to START position.

Probable Cause:

1. Overspeed LED resets and engine starts and runs. Overspeed set point is correct.

Hold verify switch on back of the SCM in VERIFY position (see Service Procedure F) and increase speed until shutdown occurs. If shut down speed is 75 percent of overspeed set point, the overspeed function is okay. Look for governor or system problems. If shut down speed is incorrect, go to Service Procedure D and check the speed sensor. 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 set point, repair governor or system problem. If speed does not go high, go to Service Procedure D and check the speed sensor. Replace the SCM if no speed sensor problem is found.

3. Overspeed set point is below specifications.

Program the correct set point according to Service Procedure A.

Problem 17: Engine shutdown occurs, low oil pressure LED is lit.

Step 1.

Test Procedure:

Turn the MCS to the OFF/RESET position.

Probable Cause:

1. The low oil pressure LED does NOT go out.

Go to Problem 14.

2. The low oil pressure LED goes out.

Check for possible causes of low oil pressure. If no causes are found, go to Step 2.

Step 2.

Test Procedure:

Check the Oil Step Speed, Rated Speed Oil Pressure Shutdown and Idle Speed Oil Pressure Shutdown settings that have been programmed into the SCM (see Service Procedure A).

Probable Cause:

1. The set points are programmed correctly.

Go to Step 3.

2. The set points are not programmed correctly.

Reprogram the SCM set points. See Service Procedure A.

Step 3.

Test Procedure:

Install a reliable oil pressure gauge. Start the engine. At idle and rated speed, check to see if the gauge and the SCM display are the same. If the oil pressure is low, do NOT continue. Shut the engine down and repair the problem in the engine lube system.

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 gauges should be installed to give operator an indication of engine conditions. If this is done, be sure to reprogram the SCM when the pressure/temperature module is replaced.

Probable Cause:

1. Gauge and SCM display are the same.

Go to Step 4.

2. Gauge and SCM display are NOT the same.

Go to Step 5.

Step 4.

Test Procedure:

At idle and rated speed, compare the measured oil pressure to the programmed set point.

Probable Cause:

1. Engine oil pressure is below the set points at low or high idle.

The problem is in the engine. Refer to the 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.

If the SCM settings are incorrect, reprogram to the correct settings. If the SCM settings are correct, correct the engine problem. Refer to the engine service manual.

Step 5.

Test Procedure:

A poor connection or short could cause the problem. Check and repair if necessary, the wiring and harness connector from the pressure/temperature module to the engine oil pressure sensor. Check if the problem is still present.

Probable Cause:

1. Problem is no longer present.

The harness was the cause of the problem.

2. Problem is still present.

Replace the oil pressure sensor. If low oil pressure problem still exists, replace the pressure/temperature module.

Problem 18: Engine shutdown occurs, high oil temperature LED is lit.

Step 1.

Test Procedure:

Turn the MCS to the OFF/RESET position. Allow the engine to cool down.

Probable Cause:

1. The high oil temperature LED does NOT go out.

Go to Problem 14.

2. The high oil temperature LED goes out.

Check for possible causes of high oil temperature. If no causes are found, go to Step 2.

Step 2.

Test Procedure:

Check the High Oil Temperature setting that has been programmed into the SCM (see Service Procedure A).

Probable Cause:

1. The set points are programmed correctly.

Go to Step 3.

2. The set points are NOT programmed correctly.

Reprogram the SCM set points. See Service Procedure A.

Step 3.

Test Procedure:

Install an accurate oil temperature gauge with the sensing bulb in an area of high oil flow, as close to the temperature probe as possible. Start the engine and allow the oil temperature to stabilize.

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

Probable Cause:

1. Temperature displayed by the SCM and by the gauge agree and it is above the temperature set point. Set Point is correct and high coolant temperature LED is lit.

Engine is overheating. Troubleshoot the oil cooling system.

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

Check the temperature probe (see Service Procedure E). If it is good, repeat test. Make sure gauge is accurate. If SCM continues to read high, replace the pressure/temperature module.

3. Temperature displayed by the SCM and by the gauge agree and are below the temperature set point.

Go to Problem 14.

4. 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 module. Check the temperature probe (see Service Procedure E).

Problem 19: Engine shutdown occurs, emergency stop LED is lit.

Test Procedure:

Reset the emergency stop push button by turning counterclockwise (CCW) until it pops out. Turn the MCS 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 MCS to reset and back to START position. If LED remains on, go to Problem 14.

Problem 20: Engine shutdown occurs, auxiliary LED is lit.

Test Procedure:

Turn the MCS to the OFF/RESET position. If the auxiliary LED does not go out, disconnect wire from terminal 13 on the SCM.

Probable Cause:

1. Auxiliary LED goes out (resets) after resetting.

Problem was auxiliary fault. Control panel is OK.

2. Auxiliary LED goes out when wire is disconnected from terminal 13.

Auxiliary shutdown relay will not reset or wire short to battery negative. Check wiring and/or replace auxiliary shutdown relay as required.

3. Auxiliary LED remains lit.

Go to Problem 14.

Problem 21: 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 (ETR). If there is no diagnostic code or fault displayed, go to Step 2.

Step 1 (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 (GSOV).

2. Engine continues to run.

Gas Shut-off Valve (GSOV) is stuck in run position. Shut engine down manually and troubleshoot GSOV.

Problem 22: Engine shutdown with no LEDs lit or diagnostic codes on SCM.

Test Procedure:

Check to make sure SCM terminal 15 is not receiving a signal to shut down (connected 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 23: Remote annunciator or remote control panel alarm module, data link controlled LEDs all flash at a rate of twice per second (0.5 Hz).

Test Procedure:

Momentarily disconnect the battery wire that is used to power the SCM. If the LEDs stop flashing after the battery is reconnected, the problem is solved. If the LEDs 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.