P20A2

P20A2-(DIESEL EXHAUST FLUID) REDUCTANT PURGE CONTROL VALVE CIRCUIT LOW




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

The Diesel Exhaust Fluid (DEF) Purge Valve is housed inside the DEF Supply Pump and is not serviceable separately. The power supply and control circuits are controlled by the DEF Dosing Control Unit. The DEF Dosing Control Unit uses the DEF Purge Valve to control the direction of the fluid flow in the DEF system. The Purge Valve position determines where diesel exhaust fluid will flow as it exits the DEF Supply Pump Assembly. The diesel exhaust fluid is pumped out of the lines and back to the tank at engine shut down to prevent the fluid from freezing in the lines. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails. The DEF Dosing Control Unit will turn off the MIL light via the PCM after the monitor runs and passes for three consecutive key cycles.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
The DEF Dosing Control Unit detects that the DEF Purge Valve control circuit is below 0.25 Volts for one second.





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, View DTCs.

Is the DTC active?

Yes

- Go To 2

No

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

2. CHECK THE (K470) DEF PURGE VALVE SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off.
2. Disconnect the DEF Supply Pump Assembly harness connector.
3. Disconnect the DEF Dosing Control Unit C1 harness connector.
4. Measure the resistance between ground and the (K470) DEF Purge Valve Signal circuit at the DEF Supply Pump Assembly harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 3

No

- Repair the (K470) DEF Purge Valve Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. CHECK THE (K421) DEF PURGE VALVE RETURN CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (K421) DEF Purge Valve Return circuit at the DEF Supply Pump Assembly harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the (K421) DEF Purge Valve Return circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE DEF PURGE VALVE
1. Reconnect the DEF Dosing Control Unit C1 harness connector.
2. Connect a jumper between the (K470) DEF Purge Valve Signal circuit and the (K421) DEF Purge Valve Return circuit at the DEF Supply Pump Assembly harness connector.

NOTE: Be careful not to spread the terminals.

3. Turn the ignition on.
4. With a scan tool, View DTCs.

Did DTC P20A3 become active and DTC P20A2 change to stored with the jumper in place?

Yes

- Replace the DEF Supply Pump Assembly. Diesel Exhaust Fluid Pump Assembly - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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