P202B

P202B-(DIESEL EXHAUST FLUID) REDUCTANT TANK HEATER CONTROL CIRCUIT LOW




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

The Diesel Exhaust Fluid (DEF) Tank has an internal heating coil to help eliminate freezing of Diesel Exhaust Fluid. The DEF Dosing Control Unit monitors the temperature of the Diesel Exhaust Fluid inside the tank. When it is determined that the Diesel Exhaust Fluid needs to be heated, the DEF Dosing Control Unit opens the DEF Engine Coolant Valve which is located nest to the DEF Tank, and allows warm engine coolant to circulate through the heating coil inside the tank to warm the Diesel Exhaust Fluid in the tank. The DEF Dosing Control Unit will illuminate the MIL lamp via the Powertrain Control Module (PCM) immediately after this diagnostic runs and fails. The DEF Dosing Control Unit will turn off the MIL lamp via the PCM immediately after the diagnostic runs and passes for three consecutive key cycles.

- When Monitored:
With the ignition on.

- Set Condition:
The DEF Dosing Control Unit detects a low signal voltage or short to ground on the (K473) DEF Engine Coolant Control Valve Signal circuit.





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

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

Is the DTC active?

Yes

- Go To 3

No

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

2. DIESEL EXHAUST FLUID ENGINE COOLANT CONTROL VALVE
1. Turn ignition off.
2. Disconnect the DEF Engine Coolant Control Valve harness connector.
3. Turn ignition on.
4. With a scan tool, View DTCs.

Does the scan tool display DTC P202A as active and P202B as stored with the DEF Dosing Control Unit C1 harness connector disconnected?

Yes

- Replace the DEF Engine Coolant Control Valve. Diesel Exhaust Fluid Engine Coolant Control Valve - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE (K473) DIESEL EXHAUST FLUID ENGINE COOLANT CONTROL VALVE SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Turn ignition off.
2. Disconnect the DEF Dosing Control Unit C1 harness connector.
3. Measure the resistance between ground and the (K473) DEF Engine Coolant Control Valve Signal circuit at the DEF Engine Coolant Control Valve harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the (K473) DEF Engine Coolant Control Valve Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE (K474) DIESEL EXHAUST FLUID ENGINE COOLANT CONTROL VALVE RETURN CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (K474) DEF Engine Coolant Control Valve Return circuit at the DEF Engine Coolant Control Valve harness connector.

Is the resistance above 10k Ohms?

Yes

- Replace the DEF Dosing Control Unit. Diesel Exhaust Fluid Dosing Control Unit - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the (K474) DEF Engine Coolant Control Valve Return circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.