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custom10nut 10-27-2021 03:11 AM
Check engine light flashing
 
I have a 91 C3500 Cheyenne (No Frills), and last year I had a no start issue,
Starting with the Fuel filter, then fuel pump, I replaced everything in the fuel system and rebuilt the TBI. Also I replaced the ignition system components, and still no start. After talking with a few heavy mechanics, we summized that the ECM was bad.
I ordered a replacement and installed it.
It started and runs fine, but from the first time, the chech engine light seems to go through a cycle of “Quick Flash” then on to a slower fash, then wil come on steady, then sometimes it will flash randomly..
One other thing is that it seems to run really rich when I first start, like it’s getting too much fuel, but runs fine after warming up.
All the electrics on the TBI are hooked up correctly. It flashes a “Bad O2sensor, but I’ve put two on it and nothing’s changed.
I was told it could be caused by the ECM not being properly set.
Anyone have any insight?:smoke:

sntrym95 10-27-2021 08:29 AM
Re: Check engine light flashing
 
Did you get the same number ECM as the old one? Also, was a chip already installed or did you swap your chip into the new one? Any info on the numbers on the ECM or chip you can provide would be helpful

Warrens69GMC 10-27-2021 11:06 AM
Re: Check engine light flashing
 
Third Generation Camaro and Firebird forum has a ton of trouble shooting TBI problems.

Yes the help us truck people as well.

https://www.thirdgen.org/forums/tbi/

custom10nut 11-01-2021 02:48 PM
Re: Check engine light flashing
 
Quote:
Originally Posted by sntrym95 (Post 8988806)
Did you get the same number ECM as the old one? Also, was a chip already installed or did you swap your chip into the new one? Any info on the numbers on the ECM or chip you can provide would be helpful
Yes it is the same.
It gets programmed according to the VIN, and yes, I put the Blue “Chip” from the original into the New.
As I said, once I put the new one it it fires up and runs fine, it’s just that light irritates me that I can’t figure out why it’s signaling

sntrym95 11-01-2021 04:12 PM
Re: Check engine light flashing
 
Quote:
Originally Posted by custom10nut (Post 8990806)
Yes it is the same.
It gets programmed according to the VIN, and yes, I put the Blue “Chip” from the original into the New.
As I said, once I put the new one it it fires up and runs fine, it’s just that light irritates me that I can’t figure out why it’s signaling
Sounds like there could also be an issue with the blue 'chip' as that contains the parameters, settings, etc. I would see about getting it reflashed or another one just to be sure.

Just call me Sean 11-01-2021 11:59 PM
Re: Check engine light flashing
 
The light flashes when you start it with the diagnostic terminal grounded, so maybe you have a bad wire.


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