P204B

P204B-(DIESEL EXHAUST FLUID) REDUCTANT PRESSURE SENSOR CIRCUIT PERFORMANCE




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. 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:
When the DEF Injector is in the priming or dosing state.

- Set Condition:
The DEF Dosing Control Unit detects that the DEF system is not able to build or maintain adequate line pressure.





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

1. CHECK THE DEF TANK LEVEL AND FLUID
1. Verify the DEF Tank level.
2. Check the fluid for signs of contamination.

Is the fluid level in the DEF Tank above the minimum requirement and free of contamination?

Yes

- Go To 2

No

- Fill the DEF Tank to the proper level with clean Diesel Exhaust Fluid. If the fluid is contaminated, follow the cleaning procedure. Procedures.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

2. ACTIVE DTC

NOTE: Perform the diagnostics for any other DEF system DTCs that are present with this fault before continuing.

1. Turn the ignition on for one minute, engine not running.
2. With the scan tool, navigate to Systems Tests and actuate the Diesel Exhaust Fluid Doser Pump Override Test.
3. With the scan tool, View DTCs.

Is the DTC active?

Yes

- Go To 3

No

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

3. CHECK FOR LEAKING DEF SUPPLY LINE OR DEF PRESSURE LINE
1. Turn the ignition off.
2. Visually inspect the DEF Supply and DEF Pressure Lines and fittings for signs of a fluid leak.

Was a leak found in the DEF system?

Yes

- Repair or replace the DEF Lines.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE DEF SUPPLY PUMP INLET FITTING AND DEF SUPPLY LINE
1. Remove the DEF Supply Line.
2. Inspect the DEF Supply Pump fitting for blockage or debris.
3. Using regulated low pressure shop air, check the DEF Supply Line for a restriction. Blow the air in the opposite direction of the fluid flow.

Were any restrictions found?

Yes

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. CHECK THE DEF SUPPLY PUMP FILTER
1. Reinstall the DEF Supply Line.
2. Remove and inspect the DEF Supply Pump Filter.

Is the DEF Supply Pump Filter blocked or restricted?

Yes

- Replace the DEF Supply Pump Filter.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 6

6. CHECK THE DEF TANK FILTER
1. Reinstall the DEF Supply Pump Filter.
2. Remove the DEF Tank Level/Temperature Sensor Assembly and inspect the DEF Tank Filter.

Is the DEF Tank Filter blocked or restricted?

Yes

- Replace the DEF Tank Level/Temperature Sensor Assembly. Diesel Exhaust Fluid Level/Temperature Sensor - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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