P208B
P208B-(DIESEL EXHAUST FLUID) REDUCTANT PUMP PERFORMANCE
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
When the DEF Dosing Control Unit is in pressure control mode, it 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 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 when the monitor runs and passes in three consecutive key cycles.
- When Monitored:
At initial key on, and when dosing is commanded on.
- Set Condition:
There are two conditions that will set this DTC. The first is if the DEF Supply Pump Assembly is not able to communicate it's internal temperature to the DEF Dosing Control Unit at key on. The second is detected at the end of the prime sequence. When the DEF Supply Pump can build and maintain 130 psi (9 bar), the DEF Dosing Control Unit will command the DEF Injector to open and looks for a pressure drop in the system. If the pressure drop does not occur, the DEF Dosing Control Unit assumes there is a blockage in the DEF Pressure Line or DEF Injector nozzle. If the DEF Dosing Control Unit detects a blockage after ten attempts, a DTC is set and diesel exhaust fluid injection into the after treatment system is disabled.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. ACTIVE DTC
NOTE: Check the fluid level in the DEF Tank before proceeding with this test procedure.
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 2
No
- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test
2. CHECK THE DEF SUPPLY LINE
1. Stop actuation of the Diesel Exhaust Fluid Doser Pump Override Test.
2. Turn the ignition off.
3. Disconnect the DEF Pressure Line.
4. Check the DEF Pressure Line for a restriction.
5. Inspect the DEF Supply Pump Assembly Outlet fitting and the DEF Injector connector and nozzle for signs of crystallization.
Is the DEF Pressure Line, DEF Supply Pump Assembly outlet fitting, and DEF Injector free of obstructions?
Yes
- Go To 2
No
- Clean the obstruction from the system or replace the blocked component if unable to clear obstruction.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
3. CHECK THE (K417) DEF SUPPLY PUMP ASSEMBLY SUPPLY CIRCUIT FOR HIGH RESISTANCE
1. Disconnect the DEF Supply Pump Assembly harness connector.
2. Disconnect the DEF Dosing Control Unit C1 harness connector.
3. Measure the resistance of the (K417) DEF Supply Pump Assembly Supply circuit between the DEF Supply Pump Assembly harness connector and the DEF Dosing Control Unit C1 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the (K417) DEF Supply Pump Assembly Supply circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
4. CHECK THE (K418) DEF SUPPLY PUMP ASSEMBLY RETURN CIRCUIT FOR HIGH RESISTANCE
1. Measure the resistance of the (K418) DEF Supply Pump Assembly Return circuit between the DEF Supply Pump Assembly harness connector and the DEF Dosing Control Unit C1 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the (K418) DEF Supply Pump Assembly Return circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
5. CHECK THE (K419) DEF SUPPLY PUMP ASSEMBLY SIGNAL CIRCUIT FOR HIGH RESISTANCE
1. Measure the resistance of the (K419) DEF Supply Pump Assembly Signal circuit between the DEF Supply Pump Assembly harness connector and the DEF Dosing Control Unit C1 harness connector.
Is the resistance below 5.0 Ohms?
Yes
- Replace the DEF Supply Pump Assembly. Diesel Exhaust Fluid Pump Assembly - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
No
- Repair the (K419) DEF Supply Pump Assembly Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.