1995 (FJ) Avenger/Sebring/Talon (2.0L DOHC, MTX)
1995 (PL) Neon

The PCM (Powertrain Control Module) may emit a high-pitched "whistle" sound after the engine is shut off. The sound may last up to eight minutes. The noise can vary in pitch and intensity from one PCM to the next and with changes in temperature and battery system voltage.

This noise is due to the PCM being "powered up" after ignition off to enable a diagnostic routine for the O2 heater operation. This diagnostic routine will only occur when certain parameters are met, which include engine operating temperature and how long the vehicle has been driven. This noise may also be heard with the ignition on and engine running, but is usually muffled by the normal engine operation sounds.

Replacing the PCM may seem to eliminate the noise for a period of time, but this is only due to the system not meeting the qualifying parameters to run the ignition off diagnostic routine.

THIS IS AN OPERATIONAL CHARACTERISTIC OF THE PCM AND NO REPAIRS
SHOULD BE ATTEMPTED.