GM Service Manual Online
For 1990-2009 cars only

DTC P1088 Without RPO CTF

Circuit Description

The common rail is installed to the intake manifold. The common rail is equipped with a flow damper, a pressure limiter, and a common rail pressure (PC) sensor.

The common rail pressure sensor is installed at left end of the common rail. The sensor serves the detect fuel pressure.

The engine control module (ECM) monitors the common rail pressure signals for voltage outside the normal range of the common rail pressure sensor. If the ECM detects a common rail pressure signal voltage that is excessively high, DTC P1088 will be set.

Conditions for Running

DTC P0192 or P0193 are not set.

Conditions for Setting the DTC

    • Common rail pressure 1st stage--common rail pressure over 160 MPa (23,205 psi) for 0.2 second
    • Common rail pressure 2nd stage--common rail pressure over 180 MPa (26,106 psi) for 0.2 second

Action Taken When the DTC Sets

    • The control module will not illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The ECM limits fuel delivery in stage 1. The ECM stops fuel delivery in stage 2.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • Poor connection at the ECM
        Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
    • A damaged harness
        Inspect the wiring harness for damage, shorts to ground, shorts to battery, and open circuits. If the harness appears to be OK, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display will indicate the location of the fault.

Step

Action

Value

Yes

No

Schematic Reference: Engine Controls Schematics

1

Is the DTC set?

--

Go to Step 2

Go to Intermittent Conditions

2

  1. Turn ON the ignition.
  2. Measure the voltage between pin number C4-19 and C4-8 and PC sensor ground at the ECM connector.

Does the voltage measure more than the specified value?

4.2 V at 160 MPa (23,205 psi)

Go to Step 5

Go to Step 3

3

Important: To start the engine, disconnect PC sensor connector.

  1. Disconnect the PC sensor harness.
  2. Clear the memory.
  3. Start the engine.

Does DTC P0088 or P1088 set?

--

Go to Step 4

Go to Step 7

4

Does the PC sensor voltage measure more than the specified voltage with the ignition ON?

3 V

Go to Step 8

Go to Step 3

5

  1. Disconnect PC sensor harness from the PC sensor and the ECM.
  2. Measure the resistance between the following points:
  3. • Between pin number C4-8 and C4-19 at the ECM harness connector and pin number 2 at the PC sensor harness connector.
    • Between PC sensor ground at the ECM harness connector and pin number 3 at the PC sensor harness connector.

Does each resistance measure less than the specified value?

0.5 ohms

Go to Step 6

Go to Step 9

6

Measure resistance between pin number C4-8 and C4-19 at the ECM harness connector and a good ground.

Does the resistance measure more than the specified value?

10 M ohms

Go to Step 8

Go to Step 10

7

Repair the poor connection at the connector.

Did you complete the repair?

--

Go to Step 13

--

8

Replace the PC sensor.

Did you complete the replacement?

--

Go to Step 11

--

9

Repair/replace the PC sensor wiring harness.

Did you complete the action?

--

Go to Step 13

--

10

Replace the PC sensor wiring harness.

Did you complete the replacement?

--

Go to Step 11

--

11

Reconnect all connectors.

Does the DTC reset?

--

Go to Step 12

Go to Step 14

12

Replace the ECM.

Did you complete the replacement?

--

Go to Step 13

--

13

Clear the DTCs.

Does the DTC reset?

--

Go to Step 2

Go to Step 14

14

Do any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

System OK