: Tell me about Force Motors/pressure control solenoids



madmathew
12-28-07, 07:52 PM
I have a code 76 on a '95 Eldorado. Its for the variable force motor which looks like it controls line pressure. Is this a common failure? I went through the diag tree and it does appear that the motor/solenoid is bad. I see them on ebay for $38 and I'm thinking about getting one from there and trying it. Looks like I need to drop the valve body down to do it, anybody else done one?

acklac7
12-28-07, 10:04 PM
This code pops up on here every once in a blue moon, very rare occurance if you ask me. That being said I've had a few issues with the pressure solenoid, in the end I attributed the problem(s) to an electrical gremlin / low battery voltage. I would throw a P076 about once every 6 months. Power-cycling the engine would often cause it to clear to history. Then one day my battery died and upon charging/starting the code set and stayed for a good hour or so. As I said before the code would typically clear if I power cycled the engine, not this time though, this time the code seemed to be stuck for good. So I gatherd my tools in preperation for a trip to the junkyard to get a used PCM (evidently corrupted PCM's can throw the pressure solenoid code). Went to start her up and to my delight the CEL was off and my Tranny was back to normal, 7000 miles later and still no CEL/P076.

I personally would try and tackle every issue OTHER than the solenoid itself, then replace the solenoid as a last resort. There have been a number of people on here who have had the solenoid replaced only to get a P076 as they pulled away from the Trans. shop :banghead:

And I believe you have to drop the trans in order to access the pressure control solenoid...Could be wrong though.

madmathew
12-28-07, 11:42 PM
I forgot to add that its a 4T80E and that it shifts like it has a pressure problem. I do know that its on the upper valve body so yes the pan and valve bodies need to come off. Did you have any hard shift issues while having codes pop up? I have a spare computer but its from a '94 so I'm not sure if it'll work, although it came with the trans. Maybe they need to go together?

acklac7
12-29-07, 12:19 AM
I forgot to add that its a 4T80E and that it shifts like it has a pressure problem. I do know that its on the upper valve body so yes the pan and valve bodies need to come off. Did you have any hard shift issues while having codes pop up? I have a spare computer but its from a '94 so I'm not sure if it'll work, although it came with the trans. Maybe they need to go together?

My Tranny would BLAST into gears whenever P076 would set, you could actually hear it "thunking" into reverse. Needless to say I thought the tranny would give at any moment, only to find out later that high line pressure actually saves the tranny somehow?



Well, its coming along. I found an engine and trans for it and transplanted those and I'll be damned if this trans doesn't have the same damn problem.

At this point I would bet money your problem lies with a faulty PCM. If you search this forum for P076 you will find a number of people who have succesfully remedied there pressure control problem by installing a new PCM. Look for the posts by Parts68, as I recall he went so far as to actually swap his faulty PCM (which kept defaulting to P076) into another mechanically sound N* Caddy, sure enough his faulty PCM immediately triggerd a P076.


And the '95 PCM and '94 PCM should be 100% compatable, as they are both OBD-I. Just make sure the '94 PCM is for a ETC I.E. L37 VIN 9 and not for a ESC (LD8 VIN Y)

Keep us updated, as I said before this problem is rather rare and I'd be interseted to see what the final outcome is.

madmathew
12-29-07, 09:19 AM
They are both for ETCs. I think I need to keep the PROM that came with the car though right?

acklac7
12-29-07, 12:24 PM
I beleive you can keep your PROM and swap out the PCM without any problems.

madmathew
12-29-07, 02:14 PM
Man, you are good! I changed out the PCM, didn't even bother with the PROM, and the problem is fixed, no more code 76. I took it for a test drive and it seems to shift right now.

acklac7
12-29-07, 03:45 PM
Good news :) suprised there isn't a TSB out regarding this issue. Interesting that the diagnostic tree led you to believe that the solenoid was bad, when in fact it was the PCM that had failed.