P204A

P204A-(DIESEL EXHAUST FLUID) REDUCTANT PRESSURE SENSOR CIRCUIT




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

The Diesel Exhaust Fluid (DEF) Pressure Sensor is a three wire sensor, integrated into the DEF Supply Pump and is not serviceable separate from the pump. The DEF Pressure Sensor monitors supply pressure to the DEF Injector. The Diesel Exhaust Fluid (DEF) Dosing Control Unit provides a 5-Volt Supply and a ground to the DEF Pressure Sensor. The sensor provides a signal to the DEF Dosing Control Unit on the DEF Pressure Sensor Signal circuit. This DEF Pressure Sensor Signal voltage changes, based on the diesel exhaust fluid pressure supplied by the DEF Supply Pump. The DEF Dosing Control Unit uses this information to vary pump speed and maintain the 130 psi (9 bar) pressure needed for proper DEF injection. The DEF Dosing Control Unit will detect a low signal voltage at low diesel exhaust fluid pressures, and a high signal voltage at high diesel exhaust fluid pressures. The DEF Dosing Control Module will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails. Diesel exhaust fluid injection into the aftertreatment system is disabled. The DEF Dosing Control Module will turn off the MIL light via the PCM when the monitor runs and passes in three consecutive key cycles.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
The DEF Dosing Control Unit detects an implausible signal from the DEF Pressure Sensor.





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 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 DEF PRESSURE SENSOR
1. Turn the ignition off.
2. Disconnect the DEF Supply Pump harness connector.
3. Turn the ignition on, engine not running.
4. With the scan tool, View DTCs.

NOTE: Other DTCs will also set from unplugging the DEF Pump Assembly. Ignore any DTCs that do not pertain to the DEF Pressure Sensor.

Did DTC P204D set as active after unplugging the connector?

Yes

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

No

- Go To 3

3. CHECK FOR THE (K422) DEF PRESSURE SENSOR SUPPLY CIRCUIT SHORTED TO ANOTHER CIRCUIT




1. Turn ignition off.
2. Disconnect the DEF Dosing Control Unit C1 harness connector.
3. Measure the resistance between the (K422) DEF Pressure Sensor Supply circuit and all other circuits at the DEF Dosing Control Unit C1 harness connector.

Is the resistance above 10k Ohms between the (K422) DEF Pressure Sensor Supply circuit and all other circuits?

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 (K422) DEF Pressure Sensor Supply circuit for a short to the circuit that measured below 10k Ohms.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.