ECM/PCM Code Description

Diagram Chart:

Diagnostic Trouble Code List

The DTCs are grouped into several types. Each type has a unique set of characteristics for the Malfunction Indicator Lamp (MIL) operation, the DTC storage, and the DTC clearing. The following list contains a brief summary of the types and the associated properties of each:

^ Type A is emissions related. The MIL illuminates, the DTC stores on the first fail and the Freeze Frame data is captured.

^ Type B is emissions related. If the fault is active for 2 consecutive driving cycles (the misfire and the fuel trim DTCs differ slightly), the MIL illuminates, the DTC stores and the Freeze Frame data is captured at the time of the second fail. At the time of the first fail, the MIL is not illuminated and no Freeze Frame data records. The DTC will appear in the memory as pending. If the next trip reports a pass, the DTC is gone.

^ Type C is non-emissions related, does not turn on the MIL, but may turn on an auxiliary service lamp if the vehicle is so equipped. The DTC stores at the time of the first fail.

^ Type D is non-emissions related and does not turn on any lamp. The DTC stores at the time of the first fail.

Special Cases Of Type B Diagnostic Tests

Unique to the misfire diagnostic, the ECM has the capability of alerting the vehicle operator to potentially damaging levels of misfire. If a misfire condition exists that could potentially damage the catalytic converter as a result of high misfire levels, the ECM will command the MIL to flash at a rate of about once per second during those the time that the catalyst damaging misfire condition is present.

The fuel trim and the misfire are special cases of type B diagnostics. Each time that a fuel trim or a misfire malfunction is detected, the engine load, the engine speed, and the engine coolant temperatures record.

When the ignition is turned off, the last reported set of conditions remain stored. During any subsequent ignition cycles, the stored conditions are used as a reference for similar conditions. If a malfunction occurs during two consecutive trips, the ECM treats the failure as a normal type B diagnostic, and does not use the stored conditions. However, if a malfunction occurs on two non-consecutive trips, the stored conditions are compared with the current conditions. The MIL will then illuminate under the following conditions:

^ When the engine load conditions are within 10% of the previous test that failed

^ When the engine speed is within 375 RPM, of the previous test that failed

^ When the engine coolant temperature is in the same range as the previous test that failed

A Fuel Trim or a Misfire DTC will overwrite any other DTC information that was stored in the Freeze Frame. However, they will not overwrite each other. The ECM DTC Type Table contains all of the Engine DTCs and their type. The DTCs that are in bold print may also set in the Transmission Control Module (TCM). Refer to Transmission and Drivetrain for the transmission system diagnosis and information.