DTC P0266 Cylinder 2 Balance System. GMC Truck Savana 2000

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Savana 🢒 DTC 🢒 DTC P0266 Cylinder 2 Balance System

Circuit Description

The 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.

•	CThe 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.

•	This conditions was met for 2 seconds.

Action Taken When the DTC Sets

•	The PCM will not illuminate the Malfunction Indicator Lamp (MIL).

•	The PCM records the operating conditions at the time the diagnostic fails. This information stores in the Failure Records.

Conditions for Clearing the MIL/DTC

•	A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.

•	Use a scan tool in order to clear the DTCs.

Diagnostic Aids

The injector balance test on the scan tool should be used in order 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:

•	Pinched or restricted fuel feed lines between the fuel tank and the fuel injection pump

•	A restricted fuel filter

Test Description

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

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

Value(s)

Yes

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

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Connect the scan tool
Start the engine.
Allow the engine to idle until the normal operating temperature is reached.
Make sure all DTCs are cleared.
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

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 the applicable DTC table

Go to Diagnostic Aids

Check for the following basic engine mechanical or fuel delivery problems in the cylinder.

•	An injection nozzle malfunction --Refer to Injection Nozzle(s) Diagnosis .

•	An intake manifold restriction.

If you find a problem, repair the condition as necessary.

Did you perform a repair?

Go to Step 6

Go to Step 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 .

Is the action complete?

Go to Step 6

Use a scan tool in order to clear the DTCs.
Start the engine.
Allow the engine to idle until the normal operating temperature is reached.
Select DTC and the Specific DTC function.
Enter the DTC number that was set.
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

Does the scan tool display any additional undiagnosed DTCs?

Go to the applicable DTC table

System OK