C6.6 Generator Set Caterpillar

This procedure tests that the correct voltage is being supplied to the Electronic Control Module (ECM).

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:

• 168-0 Electrical System Voltage high

• 168-1 Electrical System Voltage low

• 168-2 Electrical System Voltage erratic, intermittent, or incorrect

• 1834-2 Ignition Keyswitch loss of signal

The ECM receives electrical power (battery voltage) through the wiring that is supplied by the manufacturer of the application. Unswitched battery+ voltage is supplied through P1: 7, 8, 15 and 16. The battery- is supplied through P1: 1, 2, 3, 9 and 10. The ECM receives the input from the keyswitch at P1:40 when the keyswitch is in the ON position or in the START position. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down.

The cause of an intermittent power supply to the ECM can occur on either the positive side or on the negative side of the battery circuit. The connections for the unswitched battery+ may be routed through a dedicated protection device (circuit breaker).

Some applications may be equipped with an engine protection shutdown system or an idle timer shutdown system that interrupts electrical power to the keyswitch. The engine protection shutdown system can be an aftermarket device and the idle timer shutdown system can be external to the ECM. Some of these systems will not supply power to the ECM until one of the following conditions is met:

• The engine is cranked.

• The engine oil pressure achieves acceptable limits.

• An override button is pressed.

These devices may be the cause of intermittent power to the ECM. These devices may also shut down the engine.

Usually, battery power to the diagnostic connector is available and the battery power to the data link connector is independent of the keyswitch. Therefore, although it is possible to power up the electronic service tool, there may be no communication with the engine ECM. The engine ECM requires the keyswitch to be in the ON position in order to maintain communications. The ECM may power down a short time after connecting the electronic service tool if the keyswitch is in the OFF position. This is normal.

For intermittent faults such as intermittent shutdowns that could be caused by the wiring for the application, temporarily bypassing the wiring for the application may be an effective means of determining the root cause. If the symptoms disappear with the bypass wiring, the wiring for the application is the cause of the fault. A means of bypassing the wiring for the application is explained in this test procedure. This is especially important for applications that do not provide dedicated circuits for the unswitched battery and the connections for the keyswitch.

Illustration 1	g01803755
Schematic for the ignition keyswitch and battery supply circuit

Illustration 2	g01803934
View of the pin locations on the P1 connector for the ignition keyswitch and battery supply circuit (1) Battery ground (GND) (2) Battery ground (GND) (3) Battery ground (GND) (7) Battery+ (8) Battery+ (9) Battery ground (GND) (10) Battery ground (GND) (15) Battery+ (16) Battery+ (40) Ignition key switch

Test Step 1. Inspect Electrical Connectors and Wiring

1. Thoroughly inspect the P1 connector, the battery connections and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:
   • P1: 7, 8, 15, 16 (Unswitched Battery+)

   • P1: 1, 2, 3, 9, 10 (Battery-)

   • P1:40 (keyswitch)

3. Use the electronic service tool to perform a "Wiggle Test". Special attention must be paid to the following connections:
   • P1: 7, 8, 15, 16

   • P1: 1, 2, 3, 9, 10

   • P1:40

4. Check the ECM connector for the correct torque of 5.0 N·m (44 lb in).

5. Check the harness for abrasion and for pinch points from the battery to the ECM, and from the keyswitch to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness is free of corrosion, of abrasion or of pinch points.

Results:

• OK - The harness and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a fault with the connectors and/or the harness.

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 2. Check for Active Diagnostic Codes or Logged Diagnostic Codes

1. Connect the electronic service tool to the diagnostic connector.

2. Turn the keyswitch to the ON position.

3. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes or logged diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

One of the following diagnostic codes is active or logged:

• 168-0 Electrical System Voltage high

• 168-1 Electrical System Voltage low

• 168-2 Electrical System Voltage erratic, intermittent, or incorrect

• 1834-2 Ignition Keyswitch loss of signal

Note: Diagnostic code 1834-2 can be generated by rapidly cycling the keyswitch. If diagnostic code 1834-2 is logged but not active, this may be the cause.

Results:

• OK - A 168-x diagnostic code or diagnostic code 1834-2 is active or logged. Proceed to Test Step 3.

• Not OK - No diagnostic code is active.

  Repair: The fault is no longer present. If the fault is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

Test Step 3. Check the Battery Voltage at the ECM Connector

1. Disconnect the P1 connector from the ECM.

2. Turn the keyswitch to the ON position.

3. Measure the voltage between P1:7 (Unswitched Battery+) and P1:1 (Battery-).

4. Measure the voltage between P1:8 (Unswitched Battery+) and P1:2 (Battery-).

5. Measure the voltage between P1:15 (Unswitched Battery+) and P1:9 (Battery-).

6. Measure the voltage between P1:16 (keyswitch) and P1:10 (Battery-).

7. Measure the voltage between P1:40 (keyswitch) and P1:3 (Battery-).

8. Turn the keyswitch to the OFF position.

Expected Result:

For 12 Volt Systems, the measured voltage is a constant 11.0 to 13.5 Volts DC with no suspected intermittent faults at this time.

For 24 Volt Systems, the measured voltage is a constant 22.0 to 27.0 Volts DC with no suspected intermittent faults at this time.

Results:

• OK - The ECM is receiving the correct voltage.

  Repair: If an intermittent fault is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The ECM is not receiving the correct voltage. -

  Repair: Check for continuity in the harness for the keyswitch from P1:40 through the keyswitch circuit to the batteries. Check the circuit protection for the circuit.For intermittent faults such as intermittent shutdowns that could be caused by the wiring for the application, temporarily bypassing the wiring for the application may be an effective means of determining the root cause.

  Proceed to Test Step 5.

• Not OK - No Voltage on P1: 7, 8, 15, 16 - No voltage was present on P1: 7, 8, 15, 16.

  Repair: Check for continuity in the harness for the unswitched Battery+ from the ECM to the batteries. Check the circuit protection for the circuit. Check for continuity in the harness for the Battery- from the ECM to the batteries.

  Proceed to Test Step 5.

• Not OK - Battery voltage is out of range - Proceed to Test Step 4.

Test Step 4. Check the Batteries

1. Load test the batteries. Use a suitable battery load tester.

Expected Result:

The batteries pass the load test. For 12 Volt systems, the measured voltage is at least 11.0 Volts DC. For 24 Volt systems, the measured voltage is at least 22.0 Volts DC.

Results:

• OK - The batteries pass the load test. For 12 Volt systems, the measured voltage is at least 11.0 Volts DC. For 24 Volt systems, the measured voltage is at least 22.0 Volts DC.

  Repair: Refer to the service manual for the application for instructions on troubleshooting the harness for the application. Troubleshoot the harness for the application and repair the harness for the application, as required.Verify that the repairs eliminate the fault.

  STOP

• Not OK - The batteries do not pass the load test. For 12 Volt systems, the measured voltage is less than 11.0 Volts DC. For 24 Volt systems, the measured voltage is less than 22.0 Volts DC.

  Repair: Recharge or replace the faulty batteries.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 5. Bypass the Harness for the Application

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Batteries give off flammable fumes which can explode. To avoid injury or death, do not strike a match, cause a spark, or smoke in the vicinity of a battery.

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NOTICE
Do not connect the bypass harness to the battery until all of the in-line fuses have been removed from the Battery+ line. If the fuses are not removed before connection to the battery, a spark may result.

Note: This bypass harness is only for test applications. This bypass harness must be removed before the application is released to the customer. The bypass harness can be used in order to determine if the cause of the intermittent problem is interruptions in battery power to the ECM or to the keyswitch circuit.

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Illustration 3	g01803954
Schematic of the bypass harness for the application

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector from the ECM.

3. Connect a bypass harness to the ECM.

4. Remove the fuses from the Battery+ wire of the bypass harness and connect the Battery+ and the Battery- wires directly to the battery terminals.

   Note: This bypass directly connects the circuit for the keyswitch to the ECM. The ECM will remain powered until the connection to the unswitched battery+ line is disconnected. Remove the fuses from the in-line fuse holder to power down the ECM. Do not connect the bypass to the battery terminals or do not remove the bypass from the battery terminals without first removing the in-line fuses.

5. Use a multimeter to measure the voltage between P2:46 and ground. The voltage should be +5 Volts DC.

   Note: Remove the bypass harness and restore all wiring to the original condition after testing.

Expected Result:

If the measured voltage between P2:46 and ground is +5 Volts DC, installing the bypass has eliminated the fault.

Results:

• OK - The symptoms disappear when the bypass harness is installed. Also, the symptoms return when the bypass harness is removed. The fault is in the wiring for the application that supplies power to the ECM. Check for aftermarket engine protection switches that interrupt power. Send the machine to the OEM dealer to repair.STOP

• Not OK -

  Repair: Perform the following procedure:

  1. Connect the bypass to another battery and verify if the fault is resolved. If the fault is resolved, the fault is with the batteries on the application.

  2. If the fault still exists, make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

  3. Contact the Technical Communicator.

     Note: This consultation can greatly reduce the repair time.

  4. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

  5. Use the electronic service tool to recheck the system for active diagnostic codes.

  6. If the fault is resolved with the test ECM, reconnect the suspect ECM.

  7. If the fault returns with the suspect ECM, replace the ECM.

  8. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP