For 1990-2009 cars

DTC | DTC Parameters | Diagnosis
--- | --- | ---
P0601 PCM memory Important: DTC P0601 diagnostic is checked continuously | This DTC will set when the PCM determines that the ECM RAM memory is faulty. | Record all PCM DTCs and include with repair information. Replace and reprogram the PCM.
P0602 PCM not programmed Important: DTC P0602 diagnostic is checked only once as soon as the ignition is turned ON. | This DTC will set if the PCM is not programmed correctly | Record all PCM DTCs and include with the repair information. Reprogram the PCM. If this fault returns, replace and reprogram the PCM.
Important: P0601 and P0602 are (type A) DTCs