problems with replacement ECM
Thread Starter
4th Gear
Joined: Jun 2010
Posts: 4
Likes: 0
From: Benicia CA
problems with replacement ECM
I purchased a rebuilt ECM for my C4 (86) Vette, bacuase I had a few intermittent problems with my car (like the car sometimes idles high, and the ECM does no put put diagnostic codes on the ALDL connector. When I installed the replacement ECM, the car ran OK for a second or 2, and then started idling really rough. I also got a diagnostic error code for the "Spark Position" unit. I put the original ECM back into the car, and it goes back to running fine (most of the time).
Is there something special that needs to be done when the ECM is replaced (other than moving the PROM to the new ECM)?
Is there something special that needs to be done when the ECM is replaced (other than moving the PROM to the new ECM)?
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Open the and ECM door held on by two screws. Inside there is a blue colored "EPROM chip". Release the clips and remove this EPROM making careful note of its position since it can be installed backwards. Place the original EPROM in the new ECM. Should work now.
Make sure to keep track of the original EPROM and DO NOT LOOSE IT!!
Make sure to keep track of the original EPROM and DO NOT LOOSE IT!!
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
It seems lately that alot of the remanufactored items, (ecms and maf sensors) are pure junk. I got 2 remanufactored maf sensors from a company that supplys most of the east coast and both were bad. One the specs were so far off the car ran like crap and the second one I couldn't even start the car..Chances are good that you have a bad remanufactored ecm..Send it back and try again, or you can go on ebay or try on here and take a chance on a used one..Good Luck .
..WW
..WW
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
Your ECM, GM # 1227165 was used in many applications during the late 80's and early 90's. You can buy one from most any salvage yard for $35-$50. I would, make that did, that, am running an ECM that came from a 4 cylinder S-10. It is the "chip" that makes it a Corvette ECM.
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Thread Starter
4th Gear
Joined: Jun 2010
Posts: 4
Likes: 0
From: Benicia CA
If you read my posting more carefully, you will see that I DID move the PROM from the old ECM to the new one. When I installed the new ECM (with the PROM from the old ECM in it), the car ran REALLY rough.
I asked the Chevy dealer, and they said that replacing the ECM should not require the car to be re-timed.
I was wondering if anyone knew of anything (besides moving the PROM chip) that needed to be done on a Corvette when the ECM is replaced?
I asked the Chevy dealer, and they said that replacing the ECM should not require the car to be re-timed.
I was wondering if anyone knew of anything (besides moving the PROM chip) that needed to be done on a Corvette when the ECM is replaced?
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Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Finding a good used 165 is not that difficult. The price might scare you away.
Check out the the recyclers sponsoring here.
Ebay is another option. redneck43 txvetteparts and scarabexc are good to deal with.
Check out the the recyclers sponsoring here.
Ebay is another option. redneck43 txvetteparts and scarabexc are good to deal with.
Last edited by JrRifleCoach; Dec 28, 2010 at 10:04 PM.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
We used to have drive the cars till they entered closed loop for the IAC to settle down.You had no commutation to aldl with old but you do with the new? You now have a code. Car was running bad before and still is. I agree it could be a bad replacement but it could also be good and just picking up and adjusting to the issuses you have with the car. Most likely they will not take the Reman back (electrical) unless you are lucky. So you can try another one or keep testing.
