C3.4B Engines Caterpillar

Relay - Test - SCR Relay

Usage:

CCS7 4B2

This procedure covers the following diagnostic code:

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Table 1
Diagnostic Trouble Codes
J1939 Code	Code Description	Comments
5965-5	Aftertreatment #1 DEF Control Module Relay Control : Current Below Normal	The Electronic Control Module (ECM) detects an open circuit condition for the Selective Catalytic Reduction (SCR) relay control circuit for at least 2 seconds. The ECM is not attempting to activate the relay. The battery voltage is at least 10 V. The warning lamp will come on.
5965-5		The ECM detects a short circuit to battery condition for the SCR relay control circuit for at least 0.2 seconds. The ECM is attempting to activate the relay. The battery voltage is at least 10 V. The warning lamp will come on.
5965-6	Aftertreatment #1 DEF Control Module Relay Control : Current Above Normal	The ECM detects a high current condition for the SCR relay control circuit for a least 0.05 seconds. The ECM is attempting to activate the relay. The warning lamp will come on.
5965-6		The ECM detects a short circuit to ground condition for the SCR relay control circuit for at least 0.2 seconds. The ECM is not attempting to activate the relay. The battery voltage is at least 10 V. The warning lamp will come on.
5965-7	Aftertreatment #1 DEF Control Module Relay Control : Not Responding Properly	The ECM detects that the components connected to the SCR relay are not receiving power. The SCR relay has been activated. The battery voltage is at least 10 V. The warning lamp will come on.
5965-14	Aftertreatment #1 DEF Control Module Relay Control : Special Instruction	The ECM detects that the components connected to the SCR relay are still receiving power after the SCR relay has been deactivated. The battery voltage is at least 10 V. The warning lamp will come on.
Follow the troubleshooting procedure to identify the root cause of the problem.

Note: Some diagnostic codes can only be detected when the SCR relay is not active. These codes will be detected after the keyswitch has been turned to the OFF position and before the ECM main relay removes electrical power from the ECM. These diagnostic codes will be logged the next time that the keyswitch is turned to the ON position.

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Illustration 1	g06277409
Schematic diagram for the SCR relay circuit

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Illustration 2	g03730037
View of the pin location on the P2 connector for the SCR relay (20) SCR relay control

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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 P2/J2 ECM connectors and thoroughly inspect the connector for the SCR relay. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 30 N (6.7 lb) pull test on each of the wires that are associated with the SCR relay.	Damaged wire or connector	Result: A damaged wire or damaged connector was not found. The fuses are OK. Proceed to Test Step 2. 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.
2. Check for Active or Recently Logged Diagnostic Codes A. Turn the keyswitch to the OFF position. B. Connect the electronic service tool to the diagnostic connector. C. Turn the keyswitch to the ON position. D. Monitor the electronic service tool for active diagnostic codes and/or logged diagnostic codes. Note: Some diagnostic codes can only be detected when the SCR relay is not active. These codes will be detected after the keyswitch has been turned to the OFF position and before the ECM main relay removes electrical power from the ECM. These diagnostic codes will be logged the next time that the keyswitch is turned to the ON position.	Diagnostic Trouble Codes	Result: A 5965-5 diagnostic code is active (short circuit to battery). The fault is in the wiring between the SCR relay and the ECM. Repair: Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: A 5965-5 diagnostic code is recently logged (open circuit). Proceed to Test Step 3. Result: A 5965-6 diagnostic code is active (high current). Repair: Check that the correct specification of relay is installed. If necessary, install a replacement relay. Result: A 5965-6 diagnostic code is recently logged (short circuit to ground). Proceed to Test Step 6. Result: A 5965-7 diagnostic code is active. Proceed to Test Step 7. Result: A 5965-14 diagnostic code is recently logged. Proceed to Test Step 9.
3. Check the Power Supply from the ECM Main Relay A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. C. Turn the keyswitch to the ON position. D. Use a multimeter to measure the voltage between terminal 85 on the harness connector for the SCR relay and a suitable ground. E. Turn the keyswitch to the OFF position.	10 V to 14 V	Result: The measured voltage is not within the expected range. Proceed to Test Step 4. Result: The measured voltage is within the expected range. Proceed to Test Step 5.
4. Check the Wiring Between the Relay and the ECM A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. Disconnect the P2 connector. C. Use a multimeter to measure the voltage between terminal 86 on the harness connector for the relay and P2:20.	Less than 5 Ohms	Result: The measured resistance is greater than 5 Ohms. The fault is in the wiring between the SCR relay and the P2 ECM connector. Repair: Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The measured resistance is less than 5 Ohms. Contact the Dealer Solution Network (DSN).
5. Check the Wiring Between the SCR Relay and the ECM Main Relay A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay and the ECM main relay. C. Use a multimeter to measure the resistance between terminal 85 on the harness connector for the SCR main relay and terminal 87 on the harness connector for the ECM main relay.	Less than 5 Ohms	Result: The measured resistance is greater than 5 Ohms. Repair: Check the fuse. If the fuse is OK, the fault is in the wiring between the SCR relay and the ECM main relay. Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The measured resistance is less than 5 Ohms. Repair: Test the circuit for the ECM main relay. Refer to Troubleshooting, "Relay - Test (ECM Main Relay)".
6. Check the SCR Relay Wiring for a Short to Ground A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. Disconnect the P2 ECM connector. C. Use a multimeter to measure the resistance between the following points: · Terminal 85 on the harness connector for the SCR relay and a suitable ground · Terminal 86 on the harness connector for the SCR relay and a suitable ground	Greater than 1 k Ohm	Result: At least one of the resistance measurements is less than 1 k Ohm. The fault is in the wiring for the SCR relay. Repair: Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: Both resistance measurements are greater than 1 k Ohm. Repair: Install a replacement SCR relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
7. Check the Battery Supply to the SCR Relay A. Turn the keyswitch to the OFF position. B. Disconnect the SCR Relay. C. Use a multimeter to measure the voltage between terminal 30 on the harness connector for the SCR relay and a suitable ground.	10 V to 14 V	Result: The measured voltage is not within the expected range. The fault is in the battery supply wiring to the SCR relay. Repair: Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The measured voltage is within the expected range. Proceed to Test Step 8.
8. Check the Wiring Between the SCR Relay and the Aftertreatment Components A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. Disconnect the connector for the DEF pump module. Disconnect the connector for the coolant diverter valve. C. Use a multimeter to measure the resistance between terminal 87 on the harness connector for the SCR relay and the following points: · Terminal 3 on the harness connector for the DEF pump module · Terminal 5 on the harness connector for the DEF pump module · Terminal 1 on the harness connector for the coolant diverter valve.	Less than 5 Ohms	Result: At least one of the resistance measurements is greater than 5 Ohms. Repair: Check the fuses. If the fuses are OK, the fault is in the wiring between the SCR relay and the aftertreatment components. 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 the resistance measurements are less than 5 Ohms. Repair: Install a replacement SCR relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
9. Check the Voltage to the Aftertreatment Components With the SCR Relay Disconnected A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. Disconnect the connector for the DEF Pump Module. Disconnect the connector for the coolant diverter valve. C. Turn the keyswitch to the ON position. D. Use a multimeter to measure the voltage between the following points and a suitable ground: · Terminal 3 on the harness connector for the DEF pump module · Terminal 5 on the harness connector for the DEF pump module · Terminal 1 on the harness connector for the coolant diverter valve.	10 V to 14 V	Result: The voltage is within the expected range. There is a short to battery in the wiring between the SCR relay and the aftertreatment components. Repair: Replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: There is no voltage present. Repair: Install a replacement SCR relay. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.