ECM question...

Albani · Oct 2, 2016

Just bought a 96 Z71 not running. Seller claimed it just needed the new ECM flashed and new starter. I did the starter and after 5 minutes of cranking, she fired. Runs great at idle but rough when giving it gas. I guess they call this the safe mode. Tried driving around the block and transmission seemed messed up but further research showed that the ECM will also put the tranny in safe mode. Cheapest I found for ECM flash is $150 so I decided to buy a junkyard one for $28. So now she still takes a while to start, runs a little less rough when gassing it, and the best part, tranny shifting through all the gears correctly. Check engine light is on. The used ECM came from a 97 Z71. Was that a good and safe swap? I just need to pull the codes and proceed?

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df2x4 · Oct 2, 2016

Was the ECM from a truck with exactly the same equipment as yours? Same engine, transmission, gears, etc? If so you should be OK. If not, you're probably still going to need someone to flash it.

Albani · Oct 2, 2016

df2x4 said:
Was the ECM from a truck with exactly the same equipment as yours? Same engine, transmission, gears, etc? If so you should be OK. If not, you're probably still going to need someone to flash it.

It was a 350 Vortec and automatic like mine. Gears may or may not be same. Probably though.
But here is a new twist. Just got back from Autozone to get codes pulled. His code reader would not power up. He says check the fuses and or wiring. I guess that's next.

DirtBag · Oct 2, 2016

Until you read codes you really wont have any path to follow. You don't want to throw good money at it until you know its for the better.

Albani · Oct 2, 2016

So I goggled it and discovered the OBDII port shares a fuse with the lighter. Found it and it was bad. Replaced it and know the reader works. Showing misfire cylinder 8. It has new plugs and wires.

Blackwater · Oct 5, 2016

When you got the used ecm the part numbers should have matched the old one. Another thing to look at is how long was it sitting. Do a basic tune up. Spark plug and wires, timing, and maybe check the regulator. After the spark plugs and wires have the obdII read and see what faults you have. Note, you want to stay with AC Delco or simular OEM plugs. The fancy ones won't work on stock ignition systems.

Klumpper · Oct 26, 2016

something else you may try is a C.A.S.E. relearn. Tech2 can do it, EFI live on newer ECMs but i don't think the 96-97 black box is supported.... especially after an ECM swap, it's highly suggested.

df2x4 · Oct 26, 2016

Klumpper said:
something else you may try is a C.A.S.E. relearn. Tech2 can do it, EFI live on newer ECMs but i don't think the 96-97 black box is supported.... especially after an ECM swap, it's highly suggested.

CASE relearn has never been necessary for me on these trucks and I've swapped ECMs quite a bit. Unless it's throwing a code for that, you don't need to worry about it.

beardeddummy · Oct 26, 2016

It's a vortec might as well do a cap and rotor too. duralast gold is the best one I've found brass contacts and lifetime warranty. I replace mine every 10 k but I have a hot coil and the genius folks at autozone don't know if it's good or bad. there has been a lot of times when a cap and rotor has fixed a missing truck

ECM question...

Albani

Newbie

df2x4

4L60E Destroyer

Albani

Newbie

DirtBag

I'm Awesome

Albani

Newbie

Blackwater

Engineering Geinus

Klumpper

Newbie

df2x4

4L60E Destroyer

beardeddummy

I'm Awesome

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