P1C6F

P1C6F-(DIESEL EXHAUST FLUID) REDUCTANT LINE HEATER RELAY CIRCUIT PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

Each of the Diesel Exhaust Fluid (DEF) system hoses has a built in heater to warm the fluid in the lines. The three line heaters share a common power supply via the DEF Line Heater Relay which is controlled by the DEF Dosing Control Unit. The DEF Dosing Control Unit controls the heaters individually through the line heater return circuits. The three line heater circuits are monitored at the return circuit. The DEF Dosing Unit Module will illuminate the MIL light via the PCM immediately after the diagnostics runs and fails and the line heaters will be disabled. The DEF Dosing Control Unit will turn off the MIL light via the PCM immediately after the monitor runs and passes.

- When Monitored:
This monitor runs at key off.

- Set Condition:
Battery voltage has been detected at the DEF Line Heaters when the Line Heater Relay is commanded off.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on, engine not running.
2. With the scan tool check for active DTCs.

Is the DTC active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test

2. CHECK THE LINE HEATER RELAY
1. Remove the Line Heater Relay.
2. Turn the ignition off for one minute.
3. Turn the ignition on, engine not running.
4. With the scan tool check for active DTCs.

Is the DTC active?

Yes

- Repair the (K476) DEF Line Heater Output circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the Line Heater Relay.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.