C3.4B Engines Caterpillar

DEF Return Valve - Test

Usage:

CCS7 4B2

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Table 1
Diagnostic Trouble Codes for the DEF Return Valve
J1939 Code	Code Description	Comments
4376-5	Aftertreatment #1 DEF Return Valve : Current Below Normal	The Electronic Control Module (ECM) detects a low current condition on the circuit for the DEF purging pump. The battery voltage is at least 10 V. The warning lamp will come on.
4376-6	Aftertreatment #1 DEF Return Valve : Current Below Normal	The Electronic Control Module (ECM) detects a high current condition on the circuit for the DEF purging pump. The battery voltage is at least 10 V. The warning lamp will come on.
Follow the troubleshooting procedure in order to identify the root cause of the problem.

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Illustration 1	g03872333
Schematic diagram for the DEF purging pump

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Illustration 2	g03722975
View of the pin location on the P2 connector for the DEF purging pump (45) DEF purging pump ground

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Illustration 3	g03721538
Pin locations on the DEF pump module connector for the DEF purging pump (6) DEF purging pump (-) (5) DEF purging pump (+)

DEF Dosing System Purge Test

This test verifies that the DEF purging process is working correctly by purging the DEF pump and lines.

This service test is used to purge the DEF system. This test turns on the DEF purging pump, causing the DEF to be pumped from the injector back into the tank. Purging allows the system to de-pressurize and empty prior to repair work.

Navigate to the following menu options in order to access the "DEF Dosing System Purge Test":

Diagnostics
Diagnostic Tests

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Check the fuses. B. Inspect the P1/J1 ECM connectors. C. Inspect the connector for the DEF pump module. D. Perform a 30 N (6.7 lb) pull test on each of the wires in the ECM connector and the connector for the DEF pump. E. Check all of the wiring associated with the DEF pump for abrasions and pinch points.	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. Connect the electronic service tool to the diagnostic connector. Refer to Troubleshooting, "Electronic Service Tools" B. Look for active or logged diagnostic codes.	Diagnostic Trouble Codes	Result: A 4376-5 diagnostic code is active or recently logged. Proceed to Test Step 3. Result: A 4376-6 diagnostic code is active or recently logged. Proceed to Test Step 6.
3. Check the Power Supply to the DEF Purging Pump A. Turn the keyswitch to the OFF position. B. Disconnect the harness connector for the DEF pump module. C. Turn the keyswitch to the ON position. D. Use the electronic service tool to activate the "DEF Dosing System Purge Test". E. Use a multimeter to measure the voltage between terminal 5 on the harness connector fro the DEF pump and a suitable ground. F. Turn the keyswitch to the OFF position.	10 V to 14 V	Result: The measured voltage is not within the expected range. Repair: Check the fuse. If the fuse is blown, there may be a short in the wiring between the DEF pump module and the SCR relay. Replace the faulty wiring. Proceed to Test Step 7. Result: The measured voltage is within the expected range. Proceed to Test Step 5.
4. Check the Wiring Between the DEF Pump Module and the SCR Relay A. Turn the keyswitch to the OFF position. B. Disconnect the SCR relay. C. Use a multimeter to measure the resistance between terminal 5 on the harness connector for the DEF pump module and terminal 87 on the harness connector for the SCR relay.	Less than 5 Ohms	Result: The measured resistance is greater than 5 Ohms. The fault is in the wiring between the DEF pump module and the SCR relay. Repair: Replace the faulty wiring. Proceed to Test Step 7. Result: The measured resistance is less than 5 Ohms. Repair: There may be a fault in the circuit for the SCR relay. Refer to Troubleshooting, "Relay - Test (SCR Relay)" in order to Troubleshoot this circuit.
5. Create a Short Circuit at the DEF Pump Module Connector A. Turn the keyswitch to the OFF position. B. Disconnect the harness connector for the DEF pump module. C. Fabricate a jumper wire that is 150 mm (6 inch) long. D. Install the jumper wire between terminal 6 and terminal 5 on the harness connector for the DEF pump module. E. Turn the keyswitch to the ON position. F. Use the electronic service tool to activate the "DEF Dosing System Purge Test". G. Check for active diagnostic codes. H. Turn the keyswitch to the OFF position. Remove the jumper wire.	Diagnostic codes	Result: The 4376-5 diagnostic code is still active with the jumper installed. The fault is in the wiring between the DEF pump module and the ECM. Repair: Replace the faulty wiring. Proceed to Test Step 7. Result: A 4376-6 diagnostic code is active with the jumper installed. Repair: Install a replacement DEF pump module. Proceed to Test Step 7.
6. Create an Open Circuit at the DEF Pump Module Connector A. Turn the keyswitch to the OFF position. B. Disconnect the DEF pump module connector. C. Turn the keyswitch to the ON position. D. Use the electronic service tool to activate the "DEF Dosing System Purge Test". E. Check for active diagnostic codes. F. Turn the keyswitch to the OFF position.	Diagnostic codes	Result: The 4376-6 diagnostic code is still active with the DEF pump module disconnected. The fault is in the wiring between the DEF pump module connector and the P1 ECM connector. Repair: Replace the faulty wiring. Proceed to Test Step 7. Result: A 4376-5 diagnostic code is active with the DEF pump module disconnected. Repair: Install a replacement DEF pump module. Proceed to Test Step 7.
7. Run the "DEF Dosing System Purge Test" A. Reconnect all connectors. B. Turn the keyswitch to the ON position. C. Use the electronic service tool to run the "DEF Dosing System Purge Test" D. Check for active diagnostic codes.	Diagnostic codes	Result: The test completed successfully and there are no active diagnostic codes. Return the engine to service. Result: The test did not complete successfully. A 4376 diagnostic code is active. Contact the Dealer Solution Network (DSN). Result: A diagnostic ode other than a 4376 code is active. Repair: Refer to Troubleshooting, "Diagnostic Trouble Codes" in order to troubleshoot any other diagnostic codes.