C27 Engine for the AD55B Underground Articulated Truck Caterpillar

Use this test if there are intermittent engine shutdowns or if a difficulty in starting is not accompanied by loss of electrical accessories. Engine shutdowns that are accompanied by a loss of other electrical accessories indicate a problem in the keyswitch. This does not indicate a problem in the wiring at the engine's Electronic Control Module (ECM). Verify that there are no problems with the starting system or the charging system before you use this test.

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's ECM or if any one of the diagnostic codes in Table 1 is active or easily repeated.

Unswitched battery voltage is supplied to the ECM at P1-48, P1-52, and P1-53. The ground is supplied to the ECM at P1-61, P1-63, and P1-65. The ECM receives the input from the keyswitch at P1-70 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 ECM continuously receives battery voltage through the circuit breaker for the engine ECM.

The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).

Illustration 1	g01685214
Schematic for the electrical power supply circuit

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.

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Illustration 2	g01415758
Location of ECM connectors

2. Thoroughly inspect the J1/P1 ECM connectors. Inspect all of the connectors that are in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.

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Illustration 3	g01416914
P1 connections for the electrical power supply circuit (P1-48) +Battery (P1-52) +Battery (P1-53) +Battery (P1-61) −Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

4. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.

Results:

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

• Not OK - There is a problem in the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check the Battery Voltage at the ECM

1. Turn the main breaker to the OFF position.

2. Disconnect the J1/P1 ECM connector.

3. Turn the main breaker to the ON position.

4. Turn the keyswitch to the ON position.

5. Wiggle the wires in the harness while performing the following test steps.

   1. Measure the voltage between P1-48 (Unswitched +Battery) and P1-61 (−Battery).

   2. Measure the voltage between P1-52 (Unswitched +Battery) and P1-63 (−Battery).

   3. Measure the voltage between P1-53 (Unswitched +Battery) and P1-65 (−Battery).

   4. Measure the voltage between P1-70 (Keyswitch) and P1-63 (−Battery).

   5. Turn the main breaker to the OFF position.

   6. Reconnect the J1/P1 ECM connector.

Expected Result:

The measured voltage is between 22 VDC and 27 VDC.

Results:

• OK - The ECM is receiving the correct voltage.

  Repair: There may be an intermittent electrical problem in a harness or in a connector. If an intermittent condition is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Unswitched power out of range - The voltage is not correct for one of the unswitched battery circuits at the ECM. Check the wiring between the ECM and the batteries. Proceed to Test Step 4.

• Keyswitch voltage out of range - The voltage is not correct for the keyswitch circuit at the ECM. Proceed to Test Step 3.

Test Step 3. Check for Voltage at the Main Relay Contact

1. Remove wire "PU-06" from the contacts of the main relay.

2. Turn the main breaker to the ON position.

3. Turn the keyswitch to the ON position.

4. Measure the voltage between the wire "WH-06" terminal on the main relay and engine ground.

5. Measure the voltage between the wire "PU-06" terminal on the main relay and engine ground.

6. Turn the keyswitch to the OFF position.

7. Turn the main breaker to the OFF position.

8. Reconnect wire "PU-06" to the contacts of the main relay.

Expected Result:

The measured voltage is between 22 VDC and 27 VDC.

Results:

• OK - The measured voltage is between 22 VDC and 27 VDC.

  Repair: Repair the wire between the main relay and the ECM.

  STOP

• Not OK - The measured voltage is not between 22 VDC and 27 VDC on the wire "PU-06" terminal and the voltage is between 22 VDC and 27 VDC on wire "WH-06" terminal. Proceed to Test Step 5.

• Not OK - The measured voltage is not between 22 VDC and 27 VDC on wire "WH-06" terminal.

  Repair: Check the wiring between the main relay and the batteries.

  Proceed to Test Step 4.

Test Step 4. Check the Batteries

1. Measure the no-load battery voltage at the battery posts.

2. Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 and 12 Volt Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure".

Expected Result:

The batteries pass the load test. The measured voltage is the minimum specification for a 24V system.

Results:

• OK - The batteries pass the load test.

  Repair: The batteries are OK. There is an open circuit or excessive resistance in the wiring or connections between the batteries and the ECM. Verify that "CB 4" or the main breaker are not tripped. Verify that the connection at the engine ground stud is clean and tight and that the battery disconnect switch is functioning properly. Repair the connectors or wiring and/or replace the connectors or wiring between the battery and the ECM connector J1/P1.

  STOP

• Not OK - The battery voltage is low or the battery did not pass the load test.

  Repair: Recharge or replace the faulty batteries. Verify that the repair eliminates the problem.

  STOP

Test Step 5. Check the Voltage at the Keyswitch.

1. Remove the wire from the terminal R of the keyswitch.

2. Turn the keyswitch to the ON position.

3. Measure the voltage on terminal R of the keyswitch to engine ground.

4. Measure the voltage on terminal B of the keyswitch to engine ground.

5. Turn the keyswitch to the OFF position.

6. Reconnect the wire to terminal R of the keyswitch.

Expected Result:

Voltage is present on terminal R and terminal B at the keyswitch.

Results:

• OK - Voltage is present on terminal R and terminal B at the keyswitch. Proceed to Test Step 6.

• Not OK - Voltage is not present on terminal B at the keyswitch.

  Repair: If voltage is not present on terminal B, repair the circuit between the +Battery and the keyswitch. Check the circuit protection for the circuit. Verify that the problem is eliminated.

  STOP

• Not OK - Voltage is not present on terminal R at the keyswitch.

  Repair: If voltage is present on terminal B of the keyswitch but not present on terminal R, replace the keyswitch. Return all wiring to the original configuration. Verify that the problem is eliminated.

  STOP

Test Step 6. Check the Voltage at the Idle Timer and Fire Suppression Control

1. Remove wire EL308-YL from the idle timer and fire suppression control.

2. Turn the keyswitch to the ON position.

3. Measure the voltage on wire 308-YL of the idle timer and fire suppression control to engine ground.

4. Measure the voltage on terminal 2 of the idle timer and fire suppression control to engine ground.

5. Turn the keyswitch to the OFF position.

6. Reconnect all wires.

Expected Result:

The measured voltage is between 22 VDC and 27 VDC.

Results:

• OK - The measured voltage is between 22 VDC and 27 VDC. Proceed to Test Step 7.

• Not OK - The voltage is not present on wire 308-YL.

  Repair: Repair the wire between the idle timer and fire suppression control and the keyswitch. Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage is not present on terminal 2 but the voltage is present on wire 308-YL.

  Repair: Check the idle timer and fire suppression control for proper operation. If the idle timer and fire suppression control is not operating properly, replace the idle timer and fire suppression control. Verify that the repair eliminates the problem.

  STOP

Test Step 7. Check the Voltage at the Main Relay Coil

1. Remove wire E575-BU from terminal 2 of the main relay.

2. Turn the keyswitch to the ON position.

3. Measure the voltage on terminal 1 of the main relay to engine ground.

4. Measure the voltage on terminal 2 of the main relay to engine ground.

5. Turn the keyswitch to the OFF position.

6. Reconnect all wires.

Expected Result:

The measured voltage is between 22 VDC and 27 VDC.

Results:

• OK - The measured voltage is between 22 VDC and 27 VDC. Proceed to Test Step 8.

• Not OK - The voltage is not present on terminal 1.

  Repair: Repair the wire between the idle timer and fire suppression control and the main relay. Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage is not present on terminal 2.

  Repair: Replace the main relay. Verify that the repair eliminates the problem.

  STOP

Test Step 8. Check the Voltage at the Fire Suppression Control

1. Remove wire E575-BU from the fire suppression control.

2. Turn the keyswitch to the ON position.

3. Measure the voltage on wire E575-BU of the fire suppression control to engine ground.

4. Turn the keyswitch to the OFF position.

5. Reconnect all wires.

Expected Result:

The measured voltage is between 22 VDC and 27 VDC.

Results:

• OK - The measured voltage is between 22 VDC and 27 VDC.

  Repair: Check the fire suppression control for proper operation. If the fire suppression control is not operating properly, replace the fire suppression control. Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage is not present on wire E575-BU.

  Repair: Repair the wiring between the main relay and the fire suppression control. Verify that the repair eliminates the problem.

  STOP