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Thread: 1995 GMC Sierra ECM Removal

  1. #1
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    1995 GMC Sierra ECM Removal

    Looks like after changing the fuel pump,and rebuilding the pressure regulator my problem is the ECM. Removed the glovebox but it appears you need to be a GM engineer to figure out how to unplug the harness let alone remove the ECM. Anyone out there have a method to remove this thing besides a crowbar or a sawzall? It looks like there are (2) clips on the left side which secure it to somehting mounted under the ECM. If I remove those clips will it allow room to pull the ECM? I'm stumped! All help appreciated as I would like to drive this truck again someday.

  2. #2
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    You should be able to lift it up or remove those two clips and lift it up and it can be removed.

  3. #3
    Senior Moderator chevychase's Avatar
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    Like dirtrider said will come out.It is a tight fit. What makes you think you need a ecm? Injectors not firing?
    Just curious.

  4. #4
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    Chevychase Reply

    Long story:After driving ~15mi with 3 stops at about 15min. ea. on 3rd stop it would not start. After sitting ~30 min. as the tow truck driver showed up it fired up and was fine. Drove it to Napa Auto to price a fuel pump. Bought a ICM,fuel filter,rotor and cap. Installed all the next morning and drove it back into town again ~15mi. It seemed to run fine.Stopped once and the idle was up to ~1000rpm(Unusual). Drove it another mile down a hill to Staples and it sat ~15min. Then it was driven back up the hill to Napa and it was iffy on it making it up the hill as it acted if it was starved for fuel under load. Napa tested the the original ICM and it was good. I drove it home again ~15mi. One(1) mile from the house the local hiway has a stop light and my turn. After stopping annd then accelerating the transmission was shifting abnormally and again I was not sure it would make it to my house as I have a fairly long steep climb to the top. It made it to the house. Tested the fuel pressure and the pump showed on the low side with the gauge in the kit from Autozone (11psi and jittery). Bought a fuel pump from the local Chevy dealer. I dropped the tank and put the new pump in and the fuel pressure was a solid 13psi but, if you mash the accelerator it falls on it face but if you ease into the throttle it revs fine. Took it out for a test drive and again the transmission shifting is really out of whack. Not a GM mechanic but I do know the tranny is controlled by the ECM and I'm sure the lack of throttle response is related somehow. Again, if anyone has had this issue or has ideas on this I'm all ears. And, thanks everyone for the input. One other question. The ECM has the 2 clips I mentioned holding it to ?(what) which is underneath the ECM.

  5. #5
    Senior Moderator chevychase's Avatar
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    Hey aldonova... i would check your cat/ converter. sounds like it maybe stopped up. Only things i have seen that would not let one start after getting to running temp.
    cts coolant temp sensor ... a intermittent fuel pump... tps / throttle position sensor... map sensor And a clogged cat.

    On the cat check temp at inlet and outlet should be about the same. I have seen them get cherry red.
    Probably fuel related,or cat if not getting a check engine light.

  6. #6
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    ECM Removed/Installed

    Turns out the removal was not so bad. The install was a little more as one of the clips was a pain to seat completely. Anyway, ECM installed. Started truck. Same problem-falls flat on it's face if you mash the throttle. Ease into it and it's fine. No code showing. Test drive shows shift 1st-2nd good, 2nd-3rd the engine revs acts like it's never made third and does not get to OD/4th. Got a code to come up (22-TPS low voltage input) Next step- replaced the TPS. Truck starts, idles good, throttle response problem now fixed-mash the throttle no hesitation. Test drive-shift 1st-2nd good, 2nd-3rd the engine revs like it was thrown into neutral and acts like it never made 3rd and does not get to OD/4th. Is this a shift solenoid problem? Side B(2-3)? If so, easy fix? Not a tranny guy but if I can do it it'd be better than having it towed to Auburn,Ca. which is 15 miles away and probably $200 tow. This all started with the truck not starting after driving ~15 miles and several stops along the way in 90+ degree heat. Is this a coincidense for several things to fail all at once or is it a snowball effect? Have replaced the ICM,fuel pump,rebuilt the fuel pressure regulator,MAP sensor,fuel filter,ECM and now the TPS. Fuel pump was preventative maintenance though the old pump showed on the low side. Filter replaced when pump was done. Regulator was done to insure fuel train had no issues. ICM was replaced at original occurance and was a easy install though it did nothing. ECM was a gamble $100 fix-original was probably fine. TPS was replaced as I finally got a OBD1 code to come up and troubleshooting showed engine off ignition on voltage 130mv grnd. at connector to good ground on engine, positive on connector to good ground 5v. But, engine on positive to grnd closed throttle 5v and positive to grnd through throttle range 5v. No change in voltage as throttle increased. Replacement fixed the hestiation. The 2-3rd gear tranny freak out I need help with.

  7. #7
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    If you have first secobd and reverse more than likely you blew the. 3-4 clutch pack its common on the 4l60e rannys. I had this happen to me. It may have to be rebuilt there is a fix for it have them remove the load release springs.

  8. #8
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    The e.c.m requires programing at a dealer. I've had all the same problems in the same truck (4.3). Changed the e.c.m. but I haven't taken her to get programed yet, waiting on that next paycheck. I've changed everything short of the fuel pump, including every effin computer under the hood. Dropped about a grand in her before I decided to break down and do the e.c.m. She acted great for a few days, but then back to the same old attitude. Timings off, fuel regulations off, I know I have a vacume leak but not bad enough to account for everything shes doing.

  9. #9
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    since he posted this last august i hope he has it fixed!
    4 wheels move the body
    2 wheels move the soul
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    Snow is a lot like religion and a lot like sex....you never know when you are going to get it!....or how much you will get

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