GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Savana 🢒 Engine 🢒 Engine Controls - 6.5L (L65) 🢒 DTC P0263, P0266, P0269, P0272, P0275, P0278, P0281, or P0284

Circuit Description

The powertrain control module (PCM) has the ability to increase and decrease the amount of fuel to each cylinder in order to provide smooth idle operation. If the PCM determines that the fuel reduction amount to a specific cylinder exceeds the defined limits, this DTC will set. This DTC only monitors fuel reduction.

Conditions for Running the DTC
    • The engine is at idle for more than 90 seconds.
    • All engine misfire DTCs ran and passed.
    • The engine coolant is at a normal temperature.
    • The cylinder fault must be constant.

Conditions for Setting the DTC
    • The amount of fuel reduction for a specific cylinder exceeds limits that are internal to the PCM.
    • The above condition was met for 2 seconds.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • 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 non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids

The injector balance test on the scan tool should be used to confirm fault cylinder problems. The scan tool will cutout the specific cylinder requested. If a cylinder balance fault has been detected and the engine has been running for a long time, the PCM may try to increase or decrease fuel in the other cylinders in order to compensate for a rough idle. This can cause multiple cylinder balance DTCs to set. Malfunctioning nozzles are the most likely cause of cylinder balance DTCs.

If multiple cylinder balance DTCs are set and no problem is found, check for:

    • A pinched or restricted fuel feed lines between the fuel tank and the fuel injection pump
    • A restricted fuel filter

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step will properly identify a suspected cylinder by looking for a RPM drop. If the RPM drops, the cylinder is contributing. If the RPM does not drop, the cylinder is not contributing.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Important: Before clearing any DTCs, use the scan tool Capture Info function in order to save the Freeze Frame/Failure Records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Connect the scan tool.
  2. Start the engine.
  3. Allow the engine to idle until the normal operating temperature is reached.
  4. Make sure all DTCs are cleared.
  5. Using the scan tool, cutout (Inj. Balance) the suspected cylinder.

Is there an RPM drop in the suspected cylinder?

Go to Step 3

Go to Step 4

3

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs are stored, refer to the applicable DTC tables.

Are any additional DTCs stored?

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Aids

4
  1. Check for the following basic engine mechanical or fuel delivery problems in the cylinder.
    2. • An injection nozzle malfunction--Refer to Fuel Injection Nozzle Diagnosis .
    • An intake manifold restriction
  2. If you find a problem is found, repair the condition as necessary.

Did you perform a repair?

Go to Step 6

Go to Step 5

5

Important: The new injection pump must be timed. Refer to Fuel Injection Pump Timing Adjustment .

Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement .

Did you complete the replacement?

Go to Step 6

--

6
  1. Use a scan tool in order to clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the normal operating temperature is reached.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the vehicle within the Conditions for Setting this DTC until the scan tool indicates the diagnostic ran.

Does the scan tool indicate the diagnostic passed?

Go to Step 7

Go to Step 2

7

Does the scan tool display any additional undiagnosed DTCs?

Go to Diagnostic Trouble Code (DTC) List

System OK