Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's Electronic Control Module (ECM) or if any one of the diagnostic codes in Table 1 is active or easily repeated. Refer to Troubleshooting, "Event Code List" for the default conditions for event codes.
| Diagnostic Codes Table | ||
|---|---|---|
| Description | Conditions which Generate this Code | System Response |
| E043(1) Low System Voltage Warning | The battery voltage to the ECM is less than normal. | The code is logged. |
| 168-0 Electrical System Voltage high | The battery supply voltage is greater than 32 VDC for two seconds. The engine's ECM has been powered for three seconds. The engine is not being cranked. |
|
| 168-1 Electrical System Voltage low | The battery supply voltage is less than 9 VDC for two seconds. The engine's ECM has been powered for three seconds. The engine is not being cranked. |
|
| 168-2 Electrical System Voltage erratic, intermittent, or incorrect | The engine is running. The battery voltage falls below 9 VDC for at least .06 seconds. The voltage returns above 9 VDC. or Three voltage readings in the last seven seconds were below 9 VDC. |
|
To reduce resistance in the wiring harness, there are two isolated power connections to the ECM. The connections must be complete in order to ensure proper engine operation. There is a constant power supply to the ECM when the engine is shutdown. In order to shut off the power to the ECM, the main power needs to be disconnected.
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| Illustration 1 | g01286135 |
Typical schematic | |
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| Illustration 2 | g01286137 |
P1 ECM connector (P1-52) +Battery (P1-53) +Battery (P1-63) −Battery (P1-65) −Battery (P1-70) Keyswitch | |
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| Illustration 3 | g01234146 |
Location of ECM connectors | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the "main disconnect switch (MDS)" to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1. Inspect all of the other connectors. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the proper procedure for inspecting system wiring.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.
Results:
- OK - The harness and wiring are 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
- Measure no-load voltage at the battery posts. Refer to Systems Operation/Testing and Adjusting for the proper procedures to check the batteries.
- Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to the Operating Manual, SEHS9249. Refer to Special Instruction, SEHS7633.
Expected Result:
The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test.
Results:
- OK - The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test. Proceed to Test Step 3.
- Not OK - The no-load voltage at the batteries is less than 23.5 VDC, and/or the batteries fail the load test.
Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Verify that the original condition is resolved. Refer to Systems Operation/Testing and Adjusting for information on the charging system.
STOP
Test Step 3. Check the Voltage at the ECM Connector
- Disconnect the J1/P1 ECM connector that is located inside the ADEM box.
- Turn the "MDS" to the ON position.
- Wiggle the harness during the following test steps in order to find an intermittent condition.
- Measure the voltage between P1-52 (Positive Battery) and P1-63 (Negative Battery).
- Measure the voltage between P1-53 (Positive Battery) and P1-65 (Negative Battery).
- Measure the voltage between P1-70 (Keyswitch) and P1-63 (Negative Battery).
Expected Result:
The voltage is ± 1 VDC from the voltage at the battery terminals.
Results:
- OK - The ECM is receiving the correct voltage.
Repair: If an intermittent condition is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors".
STOP
- Not OK - The voltage is not ± 1 VDC from the voltage at the battery terminals. Proceed to Test Step 4.
- Not OK - Keyswitch - The voltage is not ± 1 VDC from the voltage at the battery terminals. Proceed to Test Step 5.
Test Step 4. Check the Voltage to the ECM from the Main Junction Box
- Turn the "MDS" to the OFF position.
- Remove the wire 150-WH that goes to the ECM from TB-5. Remove the wire 229-BK that goes to the ECM from TB-2.
- Turn the "MDS" to the ON position.
- Measure the voltage between TB-5 (Positive Battery) and TB-2 (Negative Battery) inside the main junction box.
Expected Result:
The voltage is ± 1 VDC from the voltage at the battery terminals.
Results:
- OK - The voltage is correct at the terminal strip inside the main junction box.
Repair: The problem is in the wiring and/or connectors between the main junction box and the ECM. Use continuity checks in order to find the open or short in the circuitry.
STOP
- Not OK - The voltage is not ± 1 VDC from the voltage at the battery terminals. The voltage is not correct at the terminal strip inside the main junction box.
Repair: There is an open circuit or excessive resistance in the wiring or connections between the batteries and the terminal strip that is inside the main junction box. Verify that the "MDS" is in the ON position and operating properly. Verify that the connection for the engine ground is clean and tight. Repair the connectors or wiring and/or replace the connectors or wiring.
STOP
Test Step 5. Check the Voltage from the Main Junction Box to the Keyswitch Input of the ECM
- Turn the "MDS" to the OFF position.
- Remove the wire 113-OR that goes to the ECM from TB-24.
- Turn the "MDS" to the ON position.
- Measure the voltage between TB-24 and TB-2 inside the main junction box.
- Turn the "MDS" to the OFF position.
- Replace all wire to the original configuration.
Expected Result:
The voltage measures 24 ± 3 VDC.
Results:
- OK - The voltage measures 24 ± 3 VDC.
Repair: There is a problem in the harness and/or connectors between TB-24 in the main junction box and the ECM. Repair the connectors and/or wiring or replace the connectors and/or wiring.
STOP
- Not OK - The voltage does not measure 24 ± 3 VDC. Proceed to Test Step 6.
Test Step 6. Check the Voltage from the Contacts of the "Main Disconnect Relay (MDR)"
- Remove the wire from terminal 14 on the "MDR" that goes to TB-24.
- Turn the "MDS" to the ON position.
- Use a voltmeter to check the voltage between terminal 14 on the "MDR" and engine ground.
- Turn the "MDS" to the OFF position.
- Replace all wire to the original configuration.
Expected Result:
The voltage measures 24 ± 3 VDC.
Results:
- OK - The voltage measures 24 ± 3 VDC.
Repair: Repair the wire between terminal 14 on the "MDR" and TB-24.
STOP
- Not OK - The voltage does not measure 24 ± 3 VDC.
Repair: Verify that the "MDR" is energizing. If the "MDR" is not energizing, check the circuit back through the following components. Refer to Illustration 1 for more information.
- TB-4
- "CB-8"
- 1A
- "MDS"
- "CB-2"
STOP
- TB-4