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Old 02-07-2006, 07:19 PM   #1
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Default 1994 ECM PCM Change Procedure

Hi all,

Mechanics said that my 1994 Oldsmobile 88 LSS engine computer needs to be changed. He is charging $285 (AC-Delco parts $220 + labor $65) for it. I hope I can save some money by doing this myself. Bought the parts from Advance AutoParts for $100 (a remanufactured parts from Cardone), but I'm scared by the wording of the warranty. Basically it says "ECM may have failed due to defective components on the vehicle. Damage to the computer caused by defective components on the vehicle WILL NOT be covered under warranty." So here I'm seeking for the correct procedures to change the ECM.

1. Retrive and record any codes from ECM.
2. Disconnect battery'* negative cable.
3. Locate and remove the ECM (OBD1: under passenger side dash. OBD2: remove air filter housing).
4. Find the cause of original ECM failure. Check resistance on each circuit controlled by ECM, test all solenoids for shorts or defects.
5. For OBD1 ECM, remove the EPROM from old unit and move it to the replacement ECM.
6. Installation is the reverse of the removal procedure.
7. Recheck all connections, then reconnect the battery negative cable.

I'm not so sure on how to do step4, so feel free to chime in on any additional details on any steps.
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Old 02-07-2006, 08:12 PM   #2
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Changin it yourself is easy.

The wording on the warrnty more or less implies "You plug it in, you own it."

Most PCMs fail of either age, or something like water got in there, or a bad wire that could have shorted or caused a voltage spike and blew it out.

But also in 94-95 model years, the PCM'* were just tossed together. GM ran out of time and cut a bunch of vital corners.

That'* about the best that I can tell you about it really.

Good luck.
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Old 02-07-2006, 08:22 PM   #3
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Default Re: 1994 ECM PCM Change Procedure

Quote:
Originally Posted by KneeHowMa
Hi all,

Mechanics said that my 1994 Oldsmobile 88 LSS engine computer needs to be changed. He is charging $285 (AC-Delco parts $220 + labor $65) for it. I hope I can save some money by doing this myself. Bought the parts from Advance AutoParts for $100 (a remanufactured parts from Cardone), but I'm scared by the wording of the warranty. Basically it says "ECM may have failed due to defective components on the vehicle. Damage to the computer caused by defective components on the vehicle WILL NOT be covered under warranty." So here I'm seeking for the correct procedures to change the ECM.

1. Retrive and record any codes from ECM.
2. Disconnect battery'* negative cable.
3. Locate and remove the ECM (OBD1: under passenger side dash. OBD2: remove air filter housing).
4. Find the cause of original ECM failure. Check resistance on each circuit controlled by ECM, test all solenoids for shorts or defects.
5. For OBD1 ECM, remove the EPROM from old unit and move it to the replacement ECM.
6. Installation is the reverse of the removal procedure.
7. Recheck all connections, then reconnect the battery negative cable.

I'm not so sure on how to do step4, so feel free to chime in on any additional details on any steps.
well what signs do we have that the PCM is failed???? I have the same car and am sorta wondering here. A part could have caused the PCM to fail but we need to know what was going on beforehand.
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Old 02-07-2006, 08:44 PM   #4
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See my post here on the problems/symptons:

http://www.bonnevilleclub.com/forum/...ic.php?t=47741

In short, car stalls randomly. Now it stalls almost immediately after engine is started. Mechanics said PCM is bad.
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Old 02-07-2006, 11:23 PM   #5
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If you have already pulled the codes, don't worry about it...

1) disconnect the battery..

2) remove the screws and the wing nuts( firewall side ) from the passenger side Hush pannel, drop or remove the hush pannel..

3) you will see the 3 connectors( wire looms ) there will be a red, blue and white connectors... There will be tabs on them... Squeeze ther tab and pull the connector( not the wires ) it may take a little tugging but the connector will come out... Remove all 3...

4) The PCM should be held in place Via a white tray with clips that hold the bottom of the PCM, just about in the area of the connectors... You will have tp push the PCM up while pusing the clips back towards the firewall.. At this point the computer should come out towards the floor...

5) Once you have removed the PCM you will then want to remove the EPROM cover via the 1/4 " screws and install the EPROM and cover onto the new PCM... And then install..

6) once you have installed the PCM, and buttoned everything up, you will want to start the car and let it idle for a few minutes... Then take it for a short drive to make sure its functioning as it should... Also you should at this point have No SES..

If there is any thing else that we can help you with, please let us know...

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Old 02-08-2006, 01:48 AM   #6
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Generally when our PCM'* fail, they throw out random codes, like not even related to the car random ****.

Also specifically to this family of cars, bad idle, voltage spike and excessive fuel consumption/nasty raw fuel smell in exhaust.
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Old 02-11-2006, 09:00 AM   #7
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Thanks to all for the input. I've swapped out the PCM (or ECM) with a remanufactured one purchased from Advance AutoPart ($106 after tax) and car is working now. Car problem started with symptons of intermitten stalls, maybe once a day. When it stalls, three lights will come up (OIL PRESSURE, HOT, VOLT), or combination of them. Towards the end, the car pretty much stalls immediately after engine is started, and sometimes it will run, but most time it won't.

I followed the procedures listed above and installed the PCM without any problem. I left the PCM out on the passenger side floor and swapped back and forth between the old PCM and new PCM, and verified that it is the PCM causing the stalling. I also noticed a low frequency buzzing sound when the old PCM is attached, but I guess it will be almost impossible to find out what circuit is shorted (or broken) in PCM and fix it yourself. BTW, found that PCM can be had at junk yard for $50-$65.
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Old 02-11-2006, 12:14 PM   #8
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Quote:
Originally Posted by KneeHowMa
Thanks to all for the input. I've swapped out the PCM (or ECM) with a remanufactured one purchased from Advance AutoPart ($106 after tax) and car is working now. Car problem started with symptons of intermitten stalls, maybe once a day. When it stalls, three lights will come up (OIL PRESSURE, HOT, VOLT), or combination of them. Towards the end, the car pretty much stalls immediately after engine is started, and sometimes it will run, but most time it won't.

I followed the procedures listed above and installed the PCM without any problem. I left the PCM out on the passenger side floor and swapped back and forth between the old PCM and new PCM, and verified that it is the PCM causing the stalling. I also noticed a low frequency buzzing sound when the old PCM is attached, but I guess it will be almost impossible to find out what circuit is shorted (or broken) in PCM and fix it yourself. BTW, found that PCM can be had at junk yard for $50-$65.
I'm not that fond of the Junk Yard units... Nor the Remans... But I'd have to think a reman may be a bit better than a junk yard unit.. Junk yard units are always a risk..

The 94-95 PCM'* do not have a good track record...

Glad you got it fixed and it running well now... Lot cheaper than having the Mechainc replace it for you ain't it...LOL.... Its always nice to be able to do it your self and save a few $$$....

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Old 11-28-2010, 01:34 AM   #9
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Default Resurrection

I know I'm resurrecting an old (2006) thread.

What I want to know is the early symptoms you had with the ECM on your 94 Olds 88.

I have a 95 Olds 98 and over the past couple of years the engine idle has gradually been changing to lower and lower rpms. It starts fine and runs reasonably smooth, just that it runs horribly slow.

Is this the sign of an ECM early failure? According to what is said in the posts it appears that 94/95 modules weren't that reliable.

I have had the car scanned, and there are no codes or history of codes. Is the ECM accessed from inside the car, or under the hood?

Hope someone can answer this. I can get a reman unit for about 185.00. If they are a simple plug and play it may be worth doing the swap.
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Old 11-29-2016, 08:19 PM   #10
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Default How do I fix this?

I'm resurrecting this thread again because I believe it is relevant (or at least google does ) and more importantly because the replies to this thread was from guys who seem to know their stuff! Let me know if I should post somewhere else.

I have a 1995 Oldsmobile 88 and I'm trying to figure out what the problem is: About 3 months ago, check engine light came on, and as I was driving home, it stalled, but I just restarted it and kept going. I had the code pulled and I was told it was the camshaft position sensor and the cruise control. However, I started to have weird things going on with the blinkers - Hazards work, but first the left blinker stopped working, and then the right not long after, then intermittently it would work again, and then it would just stay solid instead of blinking. At around this point I got a new battery. I drove the car for about 3 months, with it stalling on me more and more regularly, until it was basically at least once every trip. One day car stalled again. and I heard this super fast clicking & check engine light was blinking super fast. The a/c doesn't work and I think I hit the a/c button right before it happened. I quickly restarted car, it went another block and then wouldn't start again. I tried every day for 2 weeks to start it again, and one day I believe i hit the dash on left side of steering well and blinking stopped & I got car to start. I drove it home about 3 miles during which it must have stalled about 50 times. I got it home and never got it started again. I poked around to find out what was going on and found that one relay under the dash and another larger one in the engine bay were clicking. I tried pulling them but even so the check engine light would continue to blink rapidly. To try to figure out the problem, I pulled fuses one by one and only when pulling the large Ignition fuses (there are 2) under the hood or the ECM fuse would the relays stop clicking like mad. I was told that maybe battery went bad so relays weren't getting enough power to fully engage, so I went and got a new battery. Didn't fix. Someone wrote online that it might be the grounding bad by corrosion of wiring under the driver door panel, so i pulled that up and the conduit was completely clean almost new looking tape so I didn't bother opening it as I assume there is no corrosion. I did also pull up the passenger side and did find some minimal corrosion there, but that didn't fix the problem either. At this point I'm starting to think it is the ECM, but I don't know if I'm right - anything else I should try before swapping ECM? Just a few more things that may be relevant - at some point someone swiped driver mirror so it is hanging, but the electronic adjustment of mirror still moves the relevant parts. Drivers side speaker doesn't work as well. Also I think the driver lock/unlock all doors does not unlock/ lock the other doors but the remote does work correctly.
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