P0275

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.
^ 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 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

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 RPM drops, the cylinder is contributing. If the RPM does not drop, the cylinder is not contributing.