C3.4B Engines Electrical Power Supply

Electrical Power Supply - Test

C3.4B Engines [UENR0611]

C3.4B Engines ECM Memory - Test

C3.4B Engines Mode Selection - Test

ELECTRICAL AND STARTING SYSTEM

BATTERY GP

C3.4B Engines Battery Problem

C3.4B Engines Electrical Power Supply - Test

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

This procedure covers the following codes:

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Table 1
Diagnostic Trouble Codes for the Electrical Power Supply Circuit
J1939 Code	Code Description	Notes
168-3	Battery Potential / Power Input 1 : Voltage Above Normal	This code indicates that the battery circuit to the ECM has excessive voltage while the engine is running. The ECM detects the following conditions: The battery voltage is high for at least 5 seconds. The keyswitch is in the ON position. The engine is not cranking. The warning lamp will come on.
168-4	Battery Potential / Power Input 1 : Voltage Below Normal	This code indicates that the battery circuit for the ECM has low voltage while the engine is running. The ECM detects the following conditions: The battery voltage is low for at least 5 seconds. The keyswitch is in the ON position. The engine is not cranking. The ECM will normally log the diagnostic code. If battery voltage disappears without returning, the ECM will not log this diagnostic code and the engine will shut down. The engine may experience changes in the engine rpm, and intermittent engine shutdowns or complete engine shutdowns while the conditions that cause this diagnostic code are present.

Battery+ voltage is supplied through P1: 1, 3, and 5. The battery- is supplied through P1: 2, 4, and 6. The ECM receives the keyswitch signal at P1:54 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 activate the main relay. When battery voltage is removed from this input, after a short time (up to 60 seconds) the ECM will deactivate the main relay.

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 supply circuit.

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 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.

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Illustration 1	g03722958
Schematic diagram for the electrical power supply circuit Not all connectors are shown. Refer to the Electrical Schematic for the application.

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Illustration 2	g03722982
View of the pin locations on the P1 connector for the electrical power supply circuit (1) Battery+ (2) Battery ground (3) Battery+ (4) Battery ground (5) Battery+ (6) Battery ground (8) Start Signal (28) ECM main relay (54) Ignition key switch

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Check the fuses. B. Thoroughly inspect the battery connections and the connections to the relays. Refer to Troubleshooting, "Electrical Connector - Inspect" for details. C. Perform a 30 N (6.7 lb) pull test on each of the wires in the ECM connector that are associated with electrical power supply circuit. D. Check the harness for abrasion and for pinch points from the battery to the ECM.	Damaged wire or connector	Result: A damaged wire or damaged connector was found. A fuse is blown. Repair: Repair the damaged wire or the damaged connector. Replace any blown fuses Use the electronic service tool to clear all logged diagnostic codes. Verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly connected and/or inserted and the harness is free of corrosion, of abrasion or of pinch points. Proceed to Test Step 2.
2. Check for Active Diagnostic Codes or Logged Diagnostic Codes A. Connect the electronic service tool to the diagnostic connector. B. Turn the keyswitch to the ON position and start the engine. C. 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.	Diagnostic codes	Result: There are no active 168 diagnostic codes at this time. Repair: If the fault is intermittent, refer to Troubleshooting, "Electrical Connector - Inspect". If the ECM is receiving no battery voltage, proceed to Test Step 3. Result: There is an active 168-3 diagnostic code. Proceed to Test Step 3. Result: There is an active 168-4 diagnostic code. Proceed to Test Step 4.
3. Check the Alternator A. Test the alternator for correct operation. Refer to Systems Operation, Testing and Adjusting, "Alternator - Test".	Alternator	Result: The alternator is faulty. Repair: Replace the alternator. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The alternator is operating correctly. Proceed to Test Step 4.
4. Check the Battery A. Load-test the battery. Use a suitable battery load tester. Refer to Systems Operation, Testing and Adjusting, "Battery - Test" for the correct procedure.	Battery load test passed	Result: The battery does not pass the load test. The measured voltage is less than 11 VDC. Repair: Recharge or replace the faulty battery. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: The battery passes the load test. The measured voltage is at least 11 V. Repair: Check the wiring between the battery and the ECM. Refer to the Electrical Schematic for the application. Make any necessary repairs. If the fault is still present, contact the Dealer Solution Network (DSN).