Code 51..

I installed a different ECM (same OEM part number, switched chip after discharging my static, etc.) and now my SES light is blinking super fast. No start.
So I switched back in the original ECM, and the light is STILL blinking real fast, and when i run codes, its a code 51.

My problem is no spark, and I have run ALL the checks and tests to see why, so we figured it must be the ECM.. and now this new problem has cropped up.

Sooooo... any ECM experts want to take a stab at this? Did I fry my ECM, or is the code 51 probably gonna clear off id I ever get it started and above 40 mph?

Original help thread here, new problem pops up at the bottom of the 2nd page:
https://www.fiero.nl/forum/F...2/HTML/118063-2.html

The only reason I started a second thread here is the title has to do with ECMs and hopefully someone who knows a bit about them might click here to see what this thread is about.
Thanks for any help in advance.

diy_stu has a thread with all the codes.i donot know how to send it to you, it is my favorites.i am not computer savy and i am sending some of my luck, my msd coil is on tis way back to the company.

Yeah, I have seen the thread and know what a code 51 is supposed to mean. (New ECM recognized, bad PROM, maybe bad ECM) But what I was looking for is why the SES light was flashing a million miles an hour when I turn the key on. (Not in code-reading mode with the terminals jumped, it actually happens just when I turn the key to 'on'')

The other bad news - the ECM doesn't do anything with the spark until the engine is turning at least 400 rpm - faster than cranking speed.

GM designed the ignition that way intentionally. To eliminate any possibility of it, you can unplug the 4 wire plug that connects the ECM to the ICM if you think somehow the ECM is killing the ICM's spark.

=======

Did you make sure the prom got plugged in with the notch pointing the same way as before? Plug it in backwards and it kills the prom.

What number ECM?

[This message has been edited by phonedawgz (edited 08-18-2011).]

quote Originally posted by phonedawgz: The other bad news - the ECM doesn't do anything with the spark until the engine is turning at least 400 rpm - faster than cranking speed. GM designed the ignition that way intentionally. To eliminate any possibility of it, you can unplug the 4 wire plug that connects the ECM to the ICM if you think somehow the ECM is killing the ICM's spark.

Unplugging the 4-position connector will also disconnect the reference pulse line. Without that, there won't be any fuel injected.

quote Originally posted by phonedawgz: The other bad news - the ECM doesn't do anything with the spark until the engine is turning at least 400 rpm - faster than cranking speed. GM designed the ignition that way intentionally. To eliminate any possibility of it, you can unplug the 4 wire plug that connects the ECM to the ICM if you think somehow the ECM is killing the ICM's spark. ======= Did you make sure the prom got plugged in with the notch pointing the same way as before? Plug it in backwards and it kills the prom. What number ECM?

Typical. lol.. Just getting desperate to see if ANYTHING worked.

Yeah the chip/prom went straight from one ECM to the other in the same direction.
The ECM # was.. 1226864, same as the original one in the car I am working on.

Leaving it up to the "pros" (I hope) ... Tow Truck comes at 8am.

What does it do with no PROM installed at all? Same thing and no start?

quote Originally posted by Xanth: What does it do with no PROM installed at all? Same thing and no start?

hmm.. never tried that. Let you know tomorrow morning.

[This message has been edited by tbone42 (edited 08-19-2011).]

quote Originally posted by phonedawgz: The other bad news - the ECM doesn't do anything with the spark until the engine is turning at least 400 rpm - faster than cranking speed. GM designed the ignition that way intentionally. To eliminate any possibility of it, you can unplug the 4 wire plug that connects the ECM to the ICM if you think somehow the ECM is killing the ICM's spark.

So how does the signal from the primary ignition activate the coil if not through the ECM? Will the car start with no computer at all?

Code 51 is a faulty PROM.

Edit to add - Just read your other post.

Questions -

Did you disconnect the battery before messing with the ECU and PROM?
If not, was the ignition key in the 'OFF' position?
Is the ECM touching anything metal, or is it in it's mounting bracket?

[This message has been edited by olejoedad (edited 08-19-2011).]

quote Originally posted by olejoedad: Code 51 is a faulty PROM. Edit to add - Just read your other post. Questions - Did you disconnect the battery before messing with the ECU and PROM? If not, was the ignition key in the 'OFF' position? Is the ECM touching anything metal, or is it in it's mounting bracket?

olejoedad-
Yeah, absolutely, I unplugged the negative battery cable while switching the proms, and I was careful to not touch metal and do my static discharge, etc. And I did bolt it into the bracket while switching them and testing the 2nd ECM.
Car is in the shop now, just got back from having it towed. Its in their hands.

By the way, Jack told me you bought his 4.9 setup.. I was kinda hoping to have that as a "backup plan", but glad it went to someone I like.

Yeah, it was sitting in my barn, I just had to take it off of his hands so he wouldn't stress about selling it off piece by piece.

I plan on putting it in my 86 SE with an 88 cradle and either a Muncie or a Getrag.

Let me know if there is any help you or your mechanic need to get your car going.

https://www.fiero.nl/cgi-bin/main.cgi?ECMCodes

The rapidly flashing check engine light is normal if the ECM can't find/read the prom.
And yes, the car will start and run without a prom. It won't run well, but it will run.
This was the original "limp home" mode. The engine would run on the little chip to the left (looking at the ECM) of the prom.
(I want to say that the little chip was called a CALPAK but I could be wrong about that.)

My 3.4 coupe used to have ECM heat soak problems until I relocated the ECM to behind the passenger seat.
Whenever I would sit in traffic in the summer with the A/C on, the prom would say "buh-bye", the check engine light would start strobing, and it would run pig rich with retarded timing. Oh... and the A/C would shut down.
Once the prom cooled off, everything went back to normal.

Check your prom carefully. Make sure you didn't bend any pins. It's very easy to do and hard to see.

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Raydar
88 Formula IMSA Fastback. 4.9, NVG T550

Praise the Lowered!