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 of a Volt 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, read DTCs.

Is the DTC active?

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.

NOTE:
The P018D-FUEL PRESSURE SENSOR CIRCUIT HIGH DTC should become active or pending with the connector disconnected.

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

Is the resistance below 10k Ohms?

Yes

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

No

- Go To 4

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

Is the resistance below 10k Ohms?

Yes

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

No

- Go To 5

5. POWERTRAIN CONTROL MODULE
1.
2. Let the engine run until it reaches normal operating temperature.
3. Using the scan tool, record any DTCs.

Did the DTC return?

Yes

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

No

- Repair is complete.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.