dslpower

I have a wierd question tonight. Is the PCM supposed to give off a high pitched squeal when the key is on and engine not running????

Have been trying to figure out why the TC does'nt lock up and no cruise control. NO codes flash except 12 and 55, speedo works below 10mph, TPS adj to 1.22v at idle and goes to 3.84v w/open. It does have larger than stock diameter tires though. Cleaned and added grounds and tested ohms with a meter to get lowest reading. Everything else works fine.

Trans has been built, 1500rpm stall converter (thats when the brakes wont hold) shift kit (im guessing) It shifts fine 1-2 at 20mph 2-3at 30, o/d anywhere between 45-50. But no lock up, if i flip the switch it will lock but not automatically.
Sorry for the long post but this has been driving me crazy and then I hear the PCM squealing

v8440

I would say no, it shouldn't. Check that the mounting bolts are tight for the pcm. I think that won't stop the squealing, but check anyway. The next thing I would wonder about is whether there is a short in the wiring somewhere. The reason I say that is the pcm produces regulated 5vdc to supply to various sensors. Such supply circuits often use an oscillator to turn the 12vdc into ac, step it down with a transformer, and then use a rectifier to turn it back into dc. If those circuits are overloaded (such as by a short) then you might be hearing the oscillator struggling to supply enough current.

You may just have a bad pcm (rare), but the next thing I'd do is start unplugging the plugs connected to the pcm, one at a time, while it's squealing. When/if unplugging one stops the squealing, start checking the part of the harness connected to that plug.

dslpower

Hey guy's anybody know the Ohm values of the TCC solenoid and O/D solenoid through the harness to PCM connector?? Pins 54 & 55 to ground?

It finally threw 2 codes today 37 & 45 both indicate shorts or opens in the solenoids. also temp sensor high or low.
I can make it lock up with the switch (wired in at PCM con) so the wires are good and sol works with direct ground. And O/D works like its supposed to???
Harness not shorted to each other or ground.
Gonna get a 1k ohm resistor to by-pass the temp sensor to eliminate that, Help what am I missing????

jimk

I dont know about the values, but I used the resistor to by pass the temp switch on my 95, it may sound silly but what about the brakes switch? I also use the lockup switch when my tps switch gives me a fit. Good luck Jim

gmctd

The brake switch supplys +12v to both the TCC and Cruise circuits, so that sugg doesn't seem too silly to me

So I'll second that - check the brake\stoplite switch.

The squealing ECM may be an overloaded circuit, as mentioned above, which can cause some related and some non-related DTC's to show up

dslpower

This is driving me silly. Blue wire to cruise has 12v when switched on, good ground on black wire. Brake switch checks out OK
Everything else works properly tach,speedo, air,alt...WTS and WIF light up and go out. Unplugged sensors and connections one at a time to see if PCM would stop squealing.... it would'nt.

I will have to get a drb to scan it I guess???? Must just be fouled up on the CC and TCC circuits.