P20E8

P20E8-(DIESEL EXHAUST FLUID) REDUCTANT PRESSURE TOO LOW

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

Theory of Operation

When the DEF Dosing Control Unit is in pressure control mode, the DEF Dosing Control Unit also provides a Pulse Width Modulated (PWM) signal to turn on the DEF Supply Pump Assembly to refill the lines. As the lines fill, the pressure builds to the set point. When the pressure reaches the set point, the DEF Dosing Control Unit turns on the DEF Injector to bleed air out of the Pressure Line. Each time the injector is turned off, the DEF Dosing Control Unit the amount of time it takes for the pressure to rise back to the set point to determine when all of the air is bled out of the line. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails and diesel exhaust fluid injection into the after treatment system is disabled. The DEF Dosing Control Unit will turn off the MIL light via the PCM immediately after the monitor runs and passes.

- When Monitored:
When the Diesel Exhaust Fluid system is attempting to prime.

- Set Condition:
When the Diesel Exhaust Fluid system has been unable to successfully prime after ten attempts.





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, perform the cleaning procedure. Procedures.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

2. ACTIVE DTC
1. Turn the ignition on.
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. Intermittent Condition Test

3. CHECK THE DEF SUPPLY SYSTEM FOR LEAKS
1. During the actuation of the Diesel Exhaust Fluid Doser Pump Override Test, visually inspect the DEF Supply Pump Assembly and DEF Lines for signs of a fluid leak.

Are there any leaks in the DEF System?

Yes

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

No

- Go To 4

4. CHECK THE DEF SUPPLY LINE
1. Stop actuation of the Diesel Exhaust Fluid Doser Pump Override Test.
2. Turn the ignition off.
3. Remove the DEF Supply Line.
4. Check the DEF Supply Line for a restriction and check for crystallization on the DEF Supply Pump Assembly inlet fitting.

Is the DEF Supply Line and DEF Supply Pump Assembly fitting free of obstructions?

Yes

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

No

- Clear the restriction from the DEF Supply Line or DEF Supply Pump Assembly inlet fitting.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.