P204C
P204C-(DIESEL EXHAUST FLUID) REDUCTANT PRESSURE SENSOR CIRCUIT LOW
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:
With the ignition on.
- Set Condition:
The DEF Dosing Control Unit detects that the signal voltage from the sensor falls below 0.25 Volts for one second.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. ACTIVE DTC
NOTE: If DTC P204A is also active, perform the diagnostic procedures for that DTC before continuing with this test. P204A
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 ignition on.
4. With the scan tool check DTCs.
Did DTC P204D become active with the DEF Supply Pump harness connector disconnected?
Yes
- Go To 3
No
- Replace the DEF Supply Pump Assembly. Diesel Exhaust Fluid Pump Assembly - Removal.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
3. CHECK THE (K422) DEF PRESSURE SENSOR SUPPLY CIRCUIT FOR AN OPEN OR SHORT TO GROUND
1. Turn ignition off.
2. Disconnect the DEF Dosing Control Unit C1 harness connector.
3. Measure the resistance between ground and the (K422) DEF Pressure Sensor Supply circuit at the DEF Supply Pump harness connector.
Is the resistance above 10k Ohms?
Yes
- Go To 4
No
- Repair the (K422) DEF Pressure Sensor Supply circuit for an open circuit or short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
4. CHECK THE (K423) DEF PRESSURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Turn ignition off.
2. Disconnect the DEF Dosing Control Unit C1 harness connector.
3. Measure the resistance between ground and the (K423) DEF Pressure Sensor Signal circuit at the DEF Supply Pump harness connector.
Is the resistance above 10k Ohms?
Yes
- Go To 5
No
- Repair the (K423) DEF Pressure Sensor Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.
5. CHECK FOR THE (K423) DEF PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO THE (K424) DEF PRESSURE SENSOR GROUND CIRCUIT
1. Measure the resistance between the (K423) DEF Pressure Sensor Signal circuit and the (K424) DEF Pressure Sensor Ground circuit at the DEF Supply Pump harness connector.
Is the resistance above 10k Ohms?
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 short between the (K423) DEF Pressure Sensor Signal circuit and the (K424) DEF Pressure Sensor Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.