C4.4 and C6.6 Engines Caterpillar

Relay - Test - Start Relay

Usage:

C4.4 448

This procedure covers the following diagnostic codes:

Show/hide table

Table 1
Diagnostic Trouble Codes for the Start Relay
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
677-5	444-5	Starter Motor Relay : Current Below Normal	The Electronic Control Module (ECM) detects a low current condition (open circuit) in the start relay control circuit.
677-6	444-6	Starter Motor Relay : Current Above Normal	The Electronic Control Module (ECM) detects a high current condition (short circuit) in the start relay control circuit.
Follow the troubleshooting procedure to identify the root cause of the fault.

During the following procedure, refer to the electrical schematic for the application.

Complete the procedure in the order in which the steps are listed.

Show/hide table

Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Check that the fuses are not blown. B. Inspect the terminals on the start relay. Refer to Troubleshooting, "Electrical Connector - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the start relay wires in the ECM connector. D. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in). E. Check the harness for abrasion and pinch points from the start relay back to the ECM.	Loose connection or damaged wire	Result: There is a fault in a connector or the wiring. Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled. Replace any blown fuses. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. The fuses are not blown. Proceed to Test Step 2.
2. Check for Active Diagnostic Codes A. Connect the electronic service tool to the diagnostic connector. B. Turn the keyswitch to the ON position. Note: Do not start the engine. C. Use the electronic service tool to check for active diagnostic codes.	Diagnostic codes	Result: Diagnostic code 677-5 (444-5) is active or recently logged. Proceed to Test Step 3. Result: Diagnostic code 677-6 (444-6) is active or recently logged. Proceed to Test Step 6.
3. Check the Battery Supply Voltage at the Relay Connector A. Turn the keyswitch to the OFF position. B. Turn the keyswitch to the ON position. Do not start the engine. C. Measure the voltage between the battery input terminal on the relay and a suitable ground.	At least 11 VDC for a 12 VDC system. At least 22 VDC for a 24 VDC system.	Result: The voltage is not within the expected range. Repair: Repair or replace the battery supply wiring to the start relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The voltage is within the expected range. Proceed to Test Step 4.
4. Create a Short Circuit at the Relay Connector A. Turn the keyswitch to the OFF position. B. Remove the start relay. C. Fabricate a jumper wire. Install the jumper wire between terminal 1 and terminal 2 on the harness connector for the start relay. D. Turn the keyswitch to the ON position. E. Use the electronic service tool to check for active diagnostic codes. Wait at least 30 seconds for activation of the diagnostic codes. F. Turn the keyswitch to the OFF position and remove the jumper wire.	Diagnostic code	Result: A 677-6 (444-6) diagnostic code is active with the jumper installed. Repair: Install a replacement start relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The 677-5 (444-5) diagnostic code is still active. Proceed to Test Step 5.
5. Check the Relay Control Wiring for an Open Circuit A. Verify that the keyswitch is in the OFF position. B. Disconnect the P1 connector from the ECM. C. Inspect the P1 connector. Refer to Troubleshooting, "Electrical Connector - Inspect" for details. D. Measure the resistance between Terminal 1 on the harness connector for the start relay and the "Start Relay Control" terminal on the P1 connector. E. Measure the resistance between Terminal 2 on the harness connector for the start relay and ground.	Less than 5 Ohms	Result: At least one of the resistance measurements is greater than 5 Ohms - the fault is in the wiring for the start relay control circuit. Repair: Repair the faulty wiring or replace the faulty wiring. Result: Both resistance measurements are less than 5 Ohms. Contact the Dealer Solutions Network (DSN).
6. Create an Open Circuit at the Relay A. Turn the keyswitch to the OFF position. B. Disconnect the start relay. C. Use the electronic service tool to check for active diagnostic codes. Wait at least 30 seconds for activation of the diagnostic codes.	Diagnostic codes	Result: A 677-5 (444-5) diagnostic code is active with the relay disconnected. Repair: Install a replacement start relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The 677-6 (444-6) diagnostic code is still active with the relay disconnected. Proceed to Test Step 7.
7. Check the Wiring Between the Relay and the ECM for a Short Circuit A. Disconnect the P1 connector. B. Inspect the P1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Measure the resistance between the "Start Relay Control" terminal and all other terminals on the P1 connector.	Greater than 1.0 k Ohm	Result: At least one of the resistance measurements is less than 1.0 k Ohm. There is a short in the wiring between the relay and the ECM. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All resistance measurements are greater than 1.0 k Ohm. Contact the Dealer Solutions Network (DSN).