For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0263 11: Cylinder 1 Balance System Above Maximum Threshold
DTC P0263 12: Cylinder 1 Balance System Below Minimum Threshold
DTC P0266 11: Cylinder 2 Balance System Above Maximum Threshold
DTC P0266 12: Cylinder 2 Balance System Below Minimum Threshold
DTC P0269 11: Cylinder 3 Balance System Above Maximum Threshold
DTC P0269 12: Cylinder 3 Balance System Below Minimum Threshold
DTC P0272 11: Cylinder 4 Balance System Above Maximum Threshold
DTC P0272 12: Cylinder 4 Balance System Below Minimum Threshold

### Circuit/System Description

The ECM has the ability to increase and decrease the amount of fuel to each cylinder to provide smooth idle operation. The ECM monitors the amount of fuel required to balance each cylinder.

### Conditions for Running the DTC

• | The engine is running.

• | The DTCs run continuously when the above conditions are met.

### Conditions for Setting the DTC

The ECM detects the amount of fuel necessary to balance the system is above or below a calibrated amount.

### Action Taken When the DTC Sets

DTCs P0263, P0266, P0269, and P0272 are type C DTCs.

### Conditions for Clearing the DTC

DTCs P0263, P0266, P0269, and P0272 are type C DTCs.

### Diagnostic Aids

• | Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.

• | Perform the fuel injector coil test within the conditions of the customers concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

### Reference Information

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify no other DTCs are set.

⇒ | If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Engine running, observe the DTC information with a scan tool. DTCs P0263, P0266, P0269, and P0272 should not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, inspect for the following:

• | Low compression

• | Engine mechanical condition

• | Kinked or bent injection lines

• | Injection nozzle malfunctioning

⇒ | If a condition is found, repair as necessary.

2. If all components test normal, replace the fuel injection pump.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Injection Pump Replacement