P20C6

P20C6-(DIESEL EXHAUST FLUID) REDUCTANT HEATER D CONTROL PERFORMANCE

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

Theory of Operation

The DEF Line Heater Relay provides the power supply to DEF Line Heaters 1, 2, and 3. It is controlled by the DEF Dosing Control Unit.

- When Monitored:
The monitor runs at ignition off.

- Set Condition:
Battery voltage has been detected at the Diesel Exhaust Fluid Line Heaters when the DEF Line Heater Relay is commanded off. The Powertrain Control Module (PCM) illuminates the MIL lamp immediately after the monitor runs and fails. Diesel exhaust fluid line heating will be disabled. The PCM will turn off the MIL lamp after the monitor runs and passes.





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

1. ACTIVE DTC
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Is the DTC active?

Yes

- Go To 2

No

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

2. CHECK THE DEF LINE HEATER RELAY
1. Turn the ignition off.
2. Remove the DEF Line Heater Relay.
3. Measure the resistance between terminal 30 and terminal 87 of the DEF Line Heater Relay.

Is the resistance below 10k Ohms?

Yes

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

No

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