P0284

Diagnostic Chart:

Schematic:

CIRCUIT DESCRIPTION
The 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 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 condition 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 40 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.
2. This step will properly identity 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.