That sure sounds frustrating and stressful.
ECM issues are so hard to diagnose, other than a replace and see, or replace each and every other potential possibility, and hope.
Then they say that ECMS rarely fail on their own, but are an induced failure, from something connected to them grounding out or sending 12v to what should be 9 or 5v.
When the ECM needs to see the dealer to be reprogrammed, even more so.
My first ECM failure, I found one of the wires leading to wither lockuo or overdrive solenoid, had chafed through the insulation and was grounding out on TX bell housing.
Its replacement failed because the weight of the wire bundles, and my 'get me home' temporary fixes of the ECM connector, broke the solder connections on the ECM circuit board for intermittent issues.
Zip ties exerting pressure just so, allowed this 'temporary' fix to last a few years.
I ordered a reman ECM, it would not start my engine. sent it back.
I opened my intermittent ECM, removed potting over failed soldered pins, and did not have the confidence to resolder it myself. called around all sorts of places who refused to consider it, then got a better soldering iron and tried reflowing the solder myself.
It worked, for 4 more years.
One west to east X country journey, my aftermarket tachometer became intermittent. I was like 'I dont need no Tach, now', and 1500 miles later and a month later, found its dedicated ground wire connection I had made in haste years earlier, had failed. repaired it and the tach worked fine again. drove E to W x country again and the day after arrival, in super market parking lot, backing out of a parking spot, it stalled.
Determined no Spark, Coil tested fine..
Guessed that failed ECM was induced by intermittent Tach, as the signal wire for tach attaches to same stud on coil as that which comes from ECM.
First time I used the AAA 7 mile free tow in 18 years of membership.
ordered reman ECM, and fired right up.
a few weeks later, I bought a backup ECM, for peace of mind, but also while they were still available. With a June 1988 build date, Im surprised anything is still available for it much less a single model year ECM.
I took some steps to reduce it heating in the engine bay. Radiant and convective and routing cooler airflow through its internal heatsinks. I also made a tripod, to hold the wire bundles so that their weight and vibrations could not exert any forces on the circuit board itself.
Back 2003 or 4, before I had to learn what I now know, I was in SF and noticed my wipers moving slowly, and the blinkers blinking slowly. I had an analog voltmeter needle showing ~11 volts.
I was stuck, only able to start with the assist of a weak jumper pack. Took a bus to a parts store, and bought another battery just to be able to drive and figure it out.
I replaced the alternator with a Kragen reman, and upon engine start, the stock ammeter rose higher than I'd ever seen, then fell back to discharge.
Alternator tested good, found VR was inside engine computer, go here, there, everywhere, this place can order one. 2 days later it arrives, install it and now engine wont even start. Place who ordered it had already wrapped mine up and was about to fedex it away. I got it back just in time.
Drove to auto electrician, said please wire up an external voltage regulator.
They spent about 4 minutes, finding the fusible link, stuffed behind brake booster, had blown, spliced in a new one for 67$ and I escaped SF.
Now had they just wired up an external regulator, it would still not have charged due to this fusible link being blown.
Whats strange about the fusible link, is that their insulation is supposed to look burnt and theeasily stretch when blown. Mine did not do this, and actually tested fine after removal. The sparkies removed a 10awg fusible link and used a shorter length of 14awg, and this for many years after, all my charging current to additional batteries was forced through a 7 inch length of 14 awg bottleneck. Thing would get ridiculously hot anytime the batteries were low, until I added a parallel path.
Also if an external VR had been wired up, the check engine light would be on 24/7 and instead of the ECm adjusting fuel and spark timing via sensor inputs, it would just revert to some MPG and power killing default.
The VR inside my engine computer is now wired up to a 50 watt resistor to trick it into thinking it is still hooked to the field terminals on my alternator( NO CEL), and both my alternators are externally regulated via adjustable regulators with potentiometers on my Dash, I just got to keep voltage between 13.6 and 14.7v as 30+ seconds outside this zone will cause CEL to fire up and default to poor mpg and power settings. The CEL goes out next engine start but the code stays and the default remains until I reset ECM.
My backup ECM is inside a few layers of mylar bags and reflectix for a Faraday cage/ lesser temperature cycling effect, and every dessicant pack I can find to keep moisture at bay. I been meaning to swap the ECMS every so often.
I was ordering my ECMS through Autozone. Only the much despised Cardone remanufactured units were available, so no other choice other than to send mine out to be rebuilt. There are several options for that, which were more expensive than the cardones with AZ's online discount codes.
I never returned the ECMs cores for the 150$ fee. I still have the original. i intended to replace the capacitors in it myself just to see, but never got the round tuit needed.
Anyway, long rambling post. Sorry.
Sorry your guy is driving on the potential wild goose chase.
.
There are several outfits online who can rebuild your ECM, and they might even be able to reflash it if you provide the VIN number.
here's just one:
https://siaelec.com/product-category/ecm...ir-return/
Hope you can get it sorted out, and still enjoy your vacation.
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