I have a strong suspicion that the ECM is behind a couple of the bugs my son’s 1988 is experiencing. Finding a replacement is the biggest car chore I’ve stumbled across. It’s almost as if they are mystical relics that no vendor can clearly define.

There seems to be services that take your ECM and work their voodoo to recondition it. I’ve read several stories about that not working out well and taking way too long.

There are folks selling the ECM (all part numbers seem to be imaginary). They sell you the box (which seems to be generic to fit every GM product from the Buick Reatta to the EV1) but say you have to put your own PROM chip in it. My ECM is suspect and my PROM chip is at the center of my suspicion.

I’ve found 3 ECMs from ‘88s on eBay and the like, but they seem to come from vehicles that were totaled and left in barns. Barns that are still holding lots of barnyard animals crapping on and inside the C4s.

Is there a best practice to land a whole, fully functional ECM for my kids ‘88 that doesn’t require having my credit pulled?

 

The prom is the chip that has the vehicle tune info, ECM came in many diff vehicles including f-bodys

Recent discussion https://www.corvetteforum.com/forums...questions.html

Should be plenty of other threads on the subject

 

Is there a label on the current ECM in the son's car? Have you removed it and have it 'in hand'? Before purchasing I'd think it wise to do various diagnostics and attempt to sort it before any 'parts purchases'!

Do you have the '88 FSM - Factory Service Manual to do diagnostics?

You might best mention the issues you suspect. Does car CRANK & RUN?

'Strong Suspicion' is very similar to mentioning 'I'd like to guess'!!

 

There are a lot of things that fail before the ECM actually fails. The chip itself is not going to fail, so if thats your suspicion then you are wrong.

You need the Helm factory manual and troubleshoot the issues, which you haven't described here.

 

Thanks for the link and the info! They link was helpful. A question I did not in any way clearly ask might be - If my ECM and PROM were both severely damaged for some reason, can I buy an ECM and PROM out of another '88 Vette to replace them?

Thanks again for taking the time to reply. You've set me on a good path.

 

I will pull the ECM today and get pics of the label. I have NOT removed it (and just checking the connections should have been a no-brainer to me).

A key issue the car has is that the fans will not turn on. Replaced the primary motor and relay, jumped the A & B on the ALDL, turned the key and NOTHING. I'm new to the car. My mind went to the ECM.

I do have the '88 FSM. I can clearly understand a given diagram in about a week's time. Feeling over my head.

The car does crank and run. Runs great I believe.

The central key issue leading me to think the ECM is and issue is the fact that I can't get the fans to turn on. There may be fusible wires that I have not yet evaluated.

I truly appreciate your time. My son mowed over 300 yards to buy this beauty and I really want him to have an incredible experience.

 

OK, you clearly have a depth of experience here. It helps incredibly knowing that the chips don't fail. I have the shop manual and the electronics supplement. I'll put them to good use.

 

I would ground the fan relay according to the manual description and see if it comes on, that is all the ECM is doing. It will not come on naturally unless the AC is on, or when coolant hits 228F, unless someone has changed the chip programming.

ECM does not control the fan in front of the radiator if the car has one, that is powered by a temp switch in the cylinder head.

 

Just sent you a PM on the fan issue.

Since I see here that you've already replaced the relay, I suspect the Dk Grn/Wht wire has an open or the ECM is the problem.

Recently I picked up an ECM for my "new" '89 from my local AC Delco dealer for around $125, so they aren't really expensive. If this is the issue use caution when working on the ECM, to remove any static electricity from your body before opening up or unplugging the unit. Some like to use a wrist grounding strap but I prefer to just touch a good ground on the vehicle. Of course unplug the neg. lead on the batt. before starting.

Good luck and enjoy that '88 Vette.

 

Just a reminder that this is a 1988 coupe. The ECM turns out to be remanufactured. The ACD# on the box is 88999197. The GM# is the same. It also has LC21 4907 07074 and GR . 3 . 670 CG ECSM printed on the outer box label.

On the port for the ECM is has 07716500070730085 REMFG

The PROM is labeled DELCO ABTS 4767

I'm not well versed to say if this is the right ECM box or PROM for this vehicle. It runs fine, but there are some problems such as the handling of the primary cooling fan (we've replaced the motor, the relay and the sensor that is located near cylinder 8).

Inside the case there is some wonky looking wiring. Most noticeable is the white wire pictured below that looks like a mouse chewed on it - though that seems unlikely, and may be cause from heat?? There a a number of cold soldering joints, and I've attached a picture of Jaba the Glut holding the wire in place.

If I replace the ECM case / circuit board, what would be the spec of the one I'm looking for? I've been told that the PROM's are bullet proof and do not need to be replaced short of a fire or the chip breaking in half. Could someone have handled the chip and the circuit board without grounding themselves - I'll say yes.

Until I receive some feedback from you good folks who I am extraordinarily appreciative for, I'm going to try and replace the green/white wire that leads from the sensor to the ECM. Wish me luck.