This procedure covers the following codes:
| Diagnostic Trouble Codes | |||
|---|---|---|---|
| J1939 Code | CDL Code | Code Description | Comments |
| 168-2 | 168-2 | Battery Potential / Power Input #1 : Erratic, Intermittent, or Incorrect | This code indicates that the battery circuit to the ECM is intermittent. |
| 168-3 | 168-3 | Battery Potential / Power Input #1 : Voltage Above Normal | The ECM detects voltage that is above the acceptable value. |
| 168-4 | 168-4 | Battery Potential / Power Input 1 : Voltage Below Normal | The ECM detects voltage that is below the acceptable value. |
| Follow the troubleshooting procedure to identify the root cause of the fault. | |||
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: 48, 52, 53, 55, and 57. The battery- is supplied through P1: 61, 63, 65, 67, and 69. 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.
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 cranking.
- 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 stop 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 the electronic service tool can be powered up, there may be no communication with the engine ECM. The engine ECM requires the keyswitch to be in the ON position 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.
For intermittent faults , temporarily bypassing the application wiring may be an effective means of determining the root cause. If the symptoms disappear with the bypass wiring, the application wiring is the cause of the fault. A means of bypassing the application wiring is explained in this test procedure. This procedure is especially important for applications that do not provide dedicated circuits for the unswitched battery and the connections for the keyswitch.
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| Illustration 1 | g06151636 |
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Typical example of the schematic for the electrical power supply circuit | |
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| Illustration 2 | g01981196 |
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View of the pin locations on the P1 connector for the ignition keyswitch and battery supply circuit (48) Battery+ (52) Battery+ (53) Battery+ (55) Battery+ (57) Battery+ (61) Battery ground (63) Battery ground (65) Battery ground (67) Battery ground (69) Battery ground (70) Ignition keyswitch | |
| Troubleshooting Test Steps | Value | Results |
1. Determine the Diagnostic Code A. Establish communication between the electronic service tool and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Start the engine. Run the engine until the engine is at normal operating temperature. C. Observe the "Active Diagnostic" screen on the electronic service tool. Wait at least 30 seconds so that any codes may become active. |
Diagnostic code |
Result: One of the diagnostic codes listed in Table 1 is active. Proceed to Test Step 2. Result: The electronic service tool will not communicate with the ECM. Repair: Refer to Troubleshooting, "Electronic Service Tool Does Not Communicate". |
2. Check the Charging Circuit A. Check the charging circuit. Refer to Systems Operation, Testing and Adjusting, "Charging System - Test". |
Charging circuit |
Result: The charging system is OK. Proceed to Test Step 3. Result: The charging system is not OK. Repair: There is a fault in the charging system. Make the necessary repairs. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. |
3. Load Test the Batteries A. Use a suitable battery load tester to test the batteries. Refer to Systems Operation, Testing and Adjusting, "Battery - Test" for the correct procedure. |
Load test |
Result: The batteries pass the load test. Proceed to Test Step 4. Result: The batteries do not pass the load test. Repair: Recharge or replace the faulty batteries. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. |
4. Inspect Electrical Connectors and Wiring A. Ensure that the battery disconnect switch is in the CLOSED position. B. Thoroughly inspect all connectors associated with the electrical power supplies. C. Check all fuses. D. Perform a E. Check all the wiring associated with the electrical power supplies for abrasions and pinch points. F. Verify that the "System Operating Voltage Configuration" is correctly configured in the Engine ECM configuration parameters. |
Damaged wire or connector. Blown fuse. |
Result: A damaged wire or damaged connector was found. A blown fuse was found. Repair: Repair the damaged wire or the damaged connector. Replace all blown fuses. Use the electronic service tool to clear all logged diagnostic codes. Verify that the repair eliminates the fault. Result: The "System Operating Voltage Configuration" is configured incorrectly. Repair: Program the parameter with the correct system voltage. Result: A damaged wire or damaged connector was not found. The fuses are OK. Contact the Dealer Solutions Network (DSN). |