P018C

P018C-FUEL PRESSURE SENSOR CIRCUIT LOW

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





Theory of Operation

The Powertrain Control Module (PCM) provides a 5-Volt supply to the Fuel Rail Pressure Sensor (FRPS). The PCM also provides a ground on the sensor return circuit. The Fuel Rail Pressure Sensor provides a signal to the PCM on the Fuel Rail Pressure Sensor Signal circuit. This sensor signal voltage changes based on the pressure in the fuel rail. The PCM will detect a low signal voltage at low rail pressures. The PCM will detect a high signal voltage during high rail pressure conditions. The PCM will light the MIL lamp immediately after the diagnostic runs and fails. During this time the customer may experience a power and or speed derate. The PCM will turn off the MIL light after the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
With the ignition on and battery voltage greater than 10.4 volts.

- Set Conditions:
The circuit voltage to the Powertrain Control Module (PCM) falls below 0.25 volts for five seconds.





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

Diagnostic Test

1. ACTIVE DTC

NOTE: If a 5-Volt reference DTC is present, repair that DTC before proceeding with this test.

1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 75 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

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

2. CHECK THE FUEL RAIL PRESSURE SENSOR
1. Turn the ignition off.
2. Disconnect the FRPS harness connector.
3. Turn the ignition on.
4. With the scan tool, view DTCs.

NOTE:
The P018D-FUEL RAIL PRESSURE SENSOR CIRCUIT HIGH DTC should be active or pending with the harness connector unplugged.

Does the DTC display as described above?

Yes

- Replace the Fuel Rail Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE (K181) FUEL RAIL PRESSURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance between ground and the (K181) FRPS Signal circuit in the FRPS harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the (K181) Fuel Rail Pressure Sensor Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. CHECK FOR THE (K181) FUEL RAIL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO THE (K914) SENSOR GROUND
1. Measure the resistance between the (K181) FRPS Signal circuit and the (K914) FRPS Ground circuit at the FRPS harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 5

No

- Repair the short between the (K181) Fuel Rail Pressure Sensor Signal circuit and (K914) FRPS Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Fuel Rail Pressure Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Fuel Rail Pressure Sensor and Control Module connectors.
4. Perform any Technical Service Bulletins (TSBs) that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.