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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P1265

DTC P1265 Without RPO CTF

Circuit Description

A hydraulic piston and two-way valve (TWV) or solenoid valve have been added to the conventional nozzle. Receiving signals from the engine control module (ECM), the TWV opens and closes to change the pressure in the pressure adjustment chamber on top of the hydraulic piston so that the hydraulic piston operates, thereby ejecting the fuel from the nozzle. If the ECM detects a low voltage condition on the TWV voltage supply circuit of cylinder 4, 5, or 6 DTC P1265 will set. If the ECM detects a high voltage condition on the TWV voltage supply circuit of cylinder 4, 5, or 6 DTC P1266 will set.

Conditions for Running the DTC
    • Battery voltage is more than 10 volts.
    • There is no engine overspeed condition.

Conditions for Setting the DTC

The TWV voltage supply circuit is shorted to ground.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The ECM limits fuel delivery on cylinders 1, 2, and 3. The ECM stop fuel injection on cylinders 4, 5, and 6.

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 harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
    • Erratic RPM
    • Lack of engine power

Step

Action

Value

Yes

No

Schematic Reference: Engine Controls Schematics

1

Does the DTC set while the ignition is ON or the engine is running?

--

Go to Step 2

Go to Intermittent Conditions

2
  1. Turn OFF the ignition.
  2. Disconnect TWV harness from the TWV at the cylinder head and the engine control module (ECM).
  3. Measure the resistance between pin number C1-30 and C1-31 of the ECM and a good ground.

Does each resistance measure more than the specified value?

10 M ohms

Go to Step 3

Go to Step 4

3

Measure resistance following points at the ECM connector on the TWV harness:

    • Between pin number C1-6 of the ECM and a good ground
    • Between pin number C1-4 of the ECM and a good ground
    • Between pin number C1-2 of the ECM and a good ground

Does the resistance measure more than the specified value?

10 M ohms

Go to Step 5

Go to Step 4

4

Repair/replace the TWV harness.

Did you complete the action?

--

Go to Step 5

--

5
  1. Connect the TWV harness on both sides.
  2. Clear all DTCs.
  3. Start the engine.

Does the DTC reset?

--

Go to Step 6

Go to Step 8

6

Replace the ECM.

Did you complete the replacement?

--

Go to Step 7

--

7
  1. Clear all DTCs.
  2. Start the engine.

Does the DTC reset?

--

Go to Step 2

Go to Step 8

8

Did any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

System OK

DTC P1265 With RPO CTF

Circuit Description

The fuel 2 injector drive circuit is a high-voltage supply and drives injectors installed to cylinders 4, 5, and 6. The engine control module (ECM) steps up the battery voltage and supplies the resulted high voltage to the related injectors continuity. If the fuel 2 injector drive circuit supply to cylinder 4, 5, or 6 is short to ground circuit or if the injector solenoid control circuit 4, 5, or 6 is shorted to ground, this DTC will set.

Conditions for Running the DTC
    • The ignition switch is ON.
    • The battery voltage is between 10-16 volts.
    • The engine is running.
    • The crankshaft position (CKP) sensor is not failed.

Conditions for Setting the DTC

The ECM detects that the injector power supply circuit is short to ground circuit.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) and reduced engine power indicator lamp, if fitted, when the diagnostic runs and fails.
    • The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
    • The ECM disables cylinders 4, 5, and 6 injector operation.
    • The ECM limits fuel injection quantity for fail-safe operation.
    • The ECM closes the exhaust gas recirculation (EGR) valve and holds to close position.
    • The ECM limits fuel rail pressure for fail-safe operation.
    • The ECM limits accelerator operation range.
    • The ECM inhibits the PTO control.
    • The ECM inhibits cruise control.

Conditions for Clearing the DTC
    • The MIL resets when the ignition is turned OFF.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the MIL and the DTC with a scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Observe the failure records data fro this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  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 failure records.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Intermittent Conditions

3
  1. Turn OFF the ignition.
  2. Disconnect the injector harness in-line connector from he cylinder head cover case.
  3. Measure the resistance through the intermediate connector between the injector power supply circuits and 4, 5, and 6 injector control circuits.

Are the all resistance measures less than specified value?

2 ohms

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition.
  2. Disconnect the injector harness in-line connector from the cylinder head cover case.
  3. Measure the resistance through the intermediate connector between the injector power supply circuits and a known good ground.

Are the resistance measures more than specified value?

10M ohms

Go to Step 5

Go to Step 6

5
  1. Test the injector power supply circuits between the engine control module (ECM) and the in-line connector for a short to ground circuit.
  2. Repair the circuit, as necessary.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

6
  1. Remove the cylinder head cover.
  2. Inspect the upper portion of the appropriate injector and injector harness.
  3. Repair the condition, as necessary. Refer to Cylinder Head Replacement .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 7

7
  1. Test the injector power supply circuits between the injector terminals and the intermediate connector for the following conditions:
    2. • A short to ground circuit
    • A short to injector control circuit
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect each injector terminal from the injectors.
  3. Measure the resistance of 4, 5, and 6 injector solenoid coil.

Are the all resistance measures less than specified value?

2 ohms

Go to Step 9

Go to Step 11

9
  1. Turn OFF the ignition.
  2. Inspect for connections at the intermediate connector.
  3. Repair the connections, as necessary.

Did you find and correct the condition?

--

Go to Step 13

Go to Intermittent Conditions

10
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Inspect for poor connections at the harness connector of the ECM.
  4. Repair the connections, as necessary.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

11

Replace the appropriate injector. Refer to Fuel Injector Replacement and Fuel Injector Flow Rate Programming .

Did you complete the replacement?

--

Go to Step 13

--

12

Important: The new ECM must be programmed.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

--

Go to Step 13

--

13
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  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 Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 14

14

Observe the stored information, Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK