P0275

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) has the ability to increase and decrease the amount of fuel to each cylinder to provide smooth idle operation. If the PCM decides that the fuel reduction amount to a specific cylinder exceeds defined limits, this Diagnostic Trouble Code (DTC) will set. This DTC only monitors fuel reduction.

CONDITIONS FOR RUNNING THE DTC
^ The engine has idled for more than 90 seconds.
^ All engine misfire DTCs ran and passed.
^ The engine coolant has reached normal temperatures.
^ Any cylinder fault must be constant.

CONDITIONS FOR SETTING THE DTC
^ Amount of fuel reduction for a specific cylinder exceeds limits (internal to PCM).
^ The conditions are 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.
^ Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
The injector balance test on the scan tool should be used to confirm fault cylinder problems. The scan tool will cut out the specific cylinder requested. It is possible that if a cylinder balance fault has been detected and the engine has been running for a long time, the PCM will try to increase or decrease fuel in other cylinders to compensate for a rough idle. This can cause multiple cylinder balance DTCs to set. The scan tool snap shot mode can be used to properly identify the suspected cylinder. The most likely cause of cylinder balance DTCs are malfunctioning nozzles.

If multiple cylinder balance DTCs are set and no problem is found, check for the following conditions:
^ Pinched or restricted fuel feed lines between fuel tank and fuel injection pump
^ Restricted fuel filter

TEST DESCRIPTION

Steps 1-7:

The number below refers to the step number on the diagnostic table.
2. This step will properly identify a suspected cylinder by looking for a RPM drop. If the RPMs drop, the cylinder is contributing. If the RPMs do not drop, the cylinder is not contributing.