GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 GMC C Sierra - 2WD (CNG) 🢒 DTC 🢒 DTC P2665

Circuit Description

An ignition voltage is supplied to the low pressure lock-off (LPL) solenoid through the AF lock-off relay. The powertrain control module (PCM) controls the LPL solenoid by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P2665 sets.

Conditions for Running the DTC
    • The ignition voltage is between 6 and 18 volts.
    • The engine speed is more than 400 RPM.

Conditions for Setting the DTC
    • The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
    • The above condition exists for at least 1 second.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

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.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step determines if an AF lock-off relay condition is the cause of the concern. A faulty relay will cause DTC P0005 to also set.

    2.

  2. This step tests if the concern is active. You should hear a clicking sound when the LPL solenoid is commanded ON and OFF. Repeat the commands as necessary.

    3.

  3. This step tests the ignition voltage circuit to the LPL solenoid.

    4.

  4. This step verifies that the control module is providing ground to the LPL solenoid.

    5.

  5. This step tests if a ground is constantly being applied to the LPL solenoid.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

Is DTC P0005 also set?

Go to Fuel Lock-Off Relay Diagnosis

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Command the LPL solenoid ON and OFF with a scan tool.

Does the LPL solenoid respond to the commanded state?

Go to Step 4

Go to Step 5

4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 5

Go to Intermittent Conditions

5

  1. Turn OFF the ignition.
  2. Disconnect the LPL solenoid. Refer to Low Pressure Lock-Off Solenoid Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition voltage circuit of the LPL solenoid with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 12

6

  1. Connect a test lamp between the control circuit of the LPL solenoid and the ignition voltage circuit of the LPL solenoid.
  2. Command the LPL solenoid ON and OFF with a scan tool.

Does the test lamp turn ON and OFF with each command?

Go to Step 10

Go to Step 7

7

Does the test lamp remain illuminated with each command?

Go to Step 9

Go to Step 8

8

Test the control circuit of the LPL solenoid for an open or for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

9

Test the control circuit of the LPL solenoid for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

10

Inspect for poor connections at the LPL solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

11

Inspect for poor connections at the harness connector of the control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

12

Repair the open or short to ground in the ignition voltage circuit. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

Go to Step 15

--

13

Replace the LPL solenoid. Refer to Low Pressure Lock-Off Solenoid Replacement .

Did you complete the replacement?

Go to Step 15

--

14

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

Go to Step 15

--

15
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 16

16

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK