>> Now about my post regarding the Power Control Module... HELP
>> -Rick Mahoney
Rick-
In last e-mail you said:
>>>-
A week later the tranny started acting funny. at speeds of 65+ and after about
25-35 minutes of wartm up the tranny start shifting into and out of overdrive
This became very annoying. So I took it back to the dealer, thinking that they
had caused a problem that didn't originally exist and they told me they would
look at it. Afterwards they said they didn't think they 'caused' any problems
but... Upon checking the tranny, they said there was too much fluid in the
tranny and sometimes this could cause 'erratic shifting'. Does this sound
possible? they also told me they hooked it up to the computer and found two
codes that could 'possibly' cause thihs problem.
1) said the truck was too cold too long!(Thermostat?) and
2) that the "power control Module" indicated a problem
Questions:
1) Is is possible that a thermostat could cause this erratic shifting problem?
2) What does the Power Control Module do and does it really cost $175.00?
->>>
My Theory:
The last time my '89 was in the dealer, at 45K miles, for transmission
work the dealer put in too little fluid. This caused the OD unit to lock in
the off position. It would try to go into OD, but quickly pop out and stay
out until you turned the engine off and back on again. If you put in too much
fluid, it causes the fluid to foam, resulting in a loss of pressure. I would
imagine that the excess fluid foaming would in the same way trigger a low
fluid situation as it did for me. So, they may be right for once.
As for the temperature sensor: The temperature sensor tells the PCM
when the engine is warmed up. Until the engine is warm, the PCM will not let
the OD unit lock-up the Torque Convertor. In my truck you can watch the
temperature gauge and the tach and definitely see that once the temp gauge
gets into the "normal" zone the TC will lock and drop the tach by 200 RPM',
(Above 40 Mph).
I have never found anything stating that the OD will not engage if the
engine temp is cold. But, mine seems to delay going in if it is really cold
out, (Less than 20 deg F). Possibly, the fluid is too thick to build adequate
pressure.
I would check the coolant temp sensor as per the service manual. To do
this, put a meter on the terminals of the sensor and read the resistance with
the engine cold, warm and hot. My 89 book has a chart stating what the
resistance should be at a given engine temp. This way you can verify if your
gauge and your thermostat are OK at one time.
Good Luck!
Rob Weingart ('89 LE w/ 163K and counting)
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