Hello everyone. So I have been working on these 2.5 duke Fiero's for years and have ran into a problem I can't seem to solve. After some testing I have determined that the ECM is not sending a signal to the TBI injector. There is 12 volts going to the red wire but after a test of the node light it is in fact dead when cranking, no signal from the blue wire. This happened all of a sudden after it started up for a split second and died. No issues or drivability issues prior to it going out. Other tests included fuel pressure, spark & oil pressure, all ok. Spraying fuel directly into the TBI and it will run. I tried another ECM I got from the wrecking yard from the same year vehicle, transmission and has the same results, no signal from the blue injector wire. Any ideas on what to explore next for troubleshooting before I send it off to someone who knows about these TBI systems? Thanks for any help you can provide.

ECM turn on by switching injector to ground. Find a Noid Light to test the injector signal.
ECM doesn't run fuel injection until sees good ignition but ECM can have other problems...

Clean/fix all "grounds" bolted/screwed to whatever in the engine bay.
See my Cave, Ground "Myth" notes

Any used ECM must be same type = GM 1227748
See my Cave, 87-88 DIS Duke ECM at bottom

Used GM units maybe bad too.
Cracked solder and more can make some part "dead" while rest is working.
So Old ECM can have similar failure. More so if came from Fiero that make ECM to run hot.
See my Cave, ECM Heat

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

quote Originally posted by theogre: ECM turn on by switching injector to ground. Find a Noid Light to test the injector signal. ECM doesn't run fuel injection until sees good ignition but ECM can have other problems... Clean/fix all "grounds" bolted/screwed to whatever in the engine bay. See my Cave, Ground "Myth" notes Any used ECM must be same type = GM 1227748 See my Cave, 87-88 DIS Duke ECM at bottom Used GM units maybe bad too. Cracked solder and more can make some part "dead" while rest is working. So Old ECM can have similar failure. More so if came from Fiero that make ECM to run hot. See my Cave, ECM Heat

Thanks sir. I was having issues getting to the cave but found that Firefox is the only web browser that I have that can access it. Just out of curiosity if the crank sensor went out would it cause this? I'm assuming no because it's getting spark. Also is it common for high milage ECMs to quit like this? The ones I have tried all had around 165k miles on them including the existing one in there now.

[This message has been edited by WHIZKID355 (edited 02-11-2023).]

Now Seems Doogle Chrome and likely others based on the crap now hates shorturl.com

quote This page isn’t working fierocave.shorturl.com redirected you too many times. Try clearing your cookies. ERR_TOO_MANY_REDIRECTS

so Not my problem and cleaning cookies etc won't help.

Yes, crank sensor is fine when have spark.

25+ year old ECM can have many problems. So can Fiero Radio, Tack, and more.
Besides can "wear out" normally, Car Cabin and everything in it can heat cycle just from Sun parked outside as cabin easy hits 150+°F in "Summer" to Freezing and low in Winter.
see https://www.fiero.nl/forum/Forum2/HTML/141784.html Fiero Engine bay vs Heat.
Is worse for Fiero ECM because start hot or cold when parked and get even hotter as air is blocked so can't cool right as link above covers.
So old electronics for cars often fails.

Again, have to check/fix all grounds in the engine bay at minimum.
Take apart, clean, inspect then coat w/ silicone or permatex brake grease to prevent "rust."
Clean the engine transmission and hardware too when wire ends hit. "demmel" w/ wire wheel may help. Note wire wheel and other tips last way longer when used w/ lower speeds. Say middle speeds ~ 40-60%. Even them need eye protection and other relative PPE.