CAP 4S6836 - Caterpillar

Illustration 1 g03828378
Schematic diagram of the DEF line heater circuit
Table 2
Troubleshooting Test Steps Values Results
1. Check the Battery Voltage
A. Turn the keyswitch to the OFF position.
B. Use a suitable multimeter to measure the battery voltage.
At least 12.5 V for a 12 V system
At least 25V for a 24V system
Result: The battery voltage is lower than the expected range.
Repair: Refer to Troubleshooting, Battery Problem to investigate the cause of low battery voltage.
Result: The battery voltage is within the expected range.
Proceed to Test Step 2.
2. Inspect Electrical Connectors and Wiring
A. Thoroughly inspect the 31-pin connector for the PEU. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
B. Thoroughly inspect the connectors for the DEF line heaters. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires in the 31-pin connector and the DEF line heater connectors that are associated with the active diagnostic code.
D. Ensure that the DCU connector is securely connected and locked in place.
E. Check the harness for corrosion, abrasion, and pinch points from the DEF line heaters 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.
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.
Proceed to Test Step 3.
3. Check for Active 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. Use the electronic service tool to override each DEF line heater.
E. Verify if any of the diagnostic codes that are listed in Table 1 are active.
F. Turn the keyswitch to the OFF position.
Diagnostic codes
Result: A -5 diagnostic code is active.
Proceed to Test Step 4.
Result: A -6 diagnostic is active.
Proceed to Test Step 7.
4. Create a Short Circuit at the Harness Connector for the DEF Line Heater
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the suspect line heater.
C. Fabricate a jumper wire that is 150 mm (6 inch) long.
D. Install the wire between the two pins on the harness connector for the suspect line heater to create a short circuit.
E. Turn the keyswitch to the ON position. Use the electronic service tool to override the suspect line heater.
F. Check for active diagnostic codes.
G. Remove the jumper wire from the connector for the line heater.
Open circuit
Result: A -5 diagnostic code was active before installing the jumper. A -6 diagnostic code is active when the jumper is installed - There is a fault in the line heater.
Repair: Temporarily connect a replacement for the suspect line heater to the harness.
Turn the keyswitch to the ON position. Use the electronic service tool to override the suspect line