Dodge Neon PWM Engine comuter whines when engine is shut off

I shut off my '95 Dodge Neon and walked away noticing that the engine
control computer is making a slight whine noise that is sustained
indefinately after shutting off the engine.
If I turn the ignition on and off again then off stops. It does not
seem to do the whine thing every time and me be dependent upon
temperture.

I am wondering if anyone has ever noticed this whining "symptom" of
improper shut down to the Dodge Chrysler PWM engine control modules,
perhaps before a failure of the PWM module or other problems developing
such as a dead battery.

My understanding of the operation of the PWM electronics is that it
shuts itself off after ceasing engine operation when the ignition
switch on state is set to off because it needs to store trouble codes
etc. The PWM stores trouble history codes prior to shut down so it
turns itself off when the storage to non-volitile memory is finshed.
The '95 model is supposed to be non ODBII version when it comes to
emmissions inspections stations, i.e. they do not show it on the list
for using he ODB II connector to verify emmissions control operation
for the last 30 engine operating cycles etc., and the '95 Neon OBD II
PWM requires the Dyno-test exhaust gas analysis approach like the ODB I
version PWM models from '94 and earlier... so it may not have all OBD
II parameter monitoring and storage functions implemented as the '96
models do which do not need dyno emmissions testing. Apparently the
'95 Neon PWM was a transiton year for the ODB II implementation but I
have had a Snap On 2500 Scan Tool on it to show ovegen sensor operating
parameters and injector pulse durations so its at least a partial
implementation of OBD II.

QUESTION:
Has anyone seen this whine thing before? Is it typical of the '95 PWM
operation at times or is it unusual? Has anyone noticed this prior to
a PWM module failure?
Should I be looking for a used replacement PWM?

Please copy your response to

 

I said PWM but I meant to say PCM... Powertrain Control Module... the
engine control computer.
Sorry for any confusion...

 

The PCM may emit a high-pitched "whistle" sound after the engine is shut
off. The sound could last up to 10 minutes. The noise can vary in pitch and
intensity from one PCM to the next and with changes in temperature and
battery system voltage.

The 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.

This is a normal condition.

Glenn Beasley

Chrysler Tech