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1988 Camaro Check Engine Lights

gmbellew said:
the only thing that should make the engine light flash while driving is if it is in field service mode if ALDL terminal B is grounded (either jumpered to A, or perhaps a wiring issue). the flash speed varies based on open or closed loop. but it should not affect drivability, I don't believe.

but I've also read accounts of a bad ECM or PROM or Calpak, etc causing a flashing light while driving.

if the light comes on solid and later goes out, the code should be stored for 50 starts or power removed from the ECM for 30sec. so something strange is going on that no codes are stored.
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I’ve replaced the ECM but not the prom. I’m not driving with the OBD jumpered.
 
gmbellew said:
when you replaced the ECM, did you swap the previous PROM to the new ECM.
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Yeah. Can the prom go bad? I’m a computer guy so I have a hard time believing that static memory can go bad, but I also know anything is possible.
 
Occasionally. Actually those and the ecm are fairly stable

The probability of a wiring issue is just as or more likely
 
It’s really weird. I’m gonna let my kid empty this tank of gas then see about replacing the fuel pump. Although, it’s nice to know that all the stuff I’ve replaced is not bad and that I’ve got spares on the shelf.
 
I'd check fuel pressure before replacing a working pump.

if you still have the old ECM, might try swapping it back. or at least check to make sure the PROM is fully seated. also check the harness connections at ECM and the harness for any chaffed wires behind the glove box.

you can probably get a new PROM off ebay....just get the same number.
 
Decided against going after the fuel pump just yet. Instead I'm going to get after the Throttle body this weekend with some cleaner. Maybe even rebuild it. Upon further research maybe my IAC is bad or the TPS. I also found a way to test the EGR solenoid too.
 
If terminal B of the ALDL, or its wire, is grounded, the SES flashes at 2.5s intervals in open loop (cold engine) and 1s intervals in closed loop (warm engine). Is that what it is doing?
 
gmbellew said:
If terminal B of the ALDL, or its wire, is grounded, the SES flashes at 2.5s intervals in open loop (cold engine) and 1s intervals in closed loop (warm engine). Is that what it is doing?
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There is no specific pattern. Sometimes it doesn't flash at all other times it comes on and goes off quickly/consistently. Sometimes it starts to light up and goes right out.
 
Still chasing gremlins…..here’s the thing though, the Check Engine Light flashes when the ignition is on and the car is not running. This has got to be an electrical problem somewhere right? I’m pretty sure it’s always been this way, but I’m not sure anymore.

We added a stereo when we got it, but it ran fine for months before this CEL problem started. However, the stereo quit working this morning and I can’t help but think it’s all related somehow.

Looking for any suggestions, but really just need to share my frustrations.

Happy Thanksgiving!
 
Is it flashing in a controlled pattern, or does it look like its flickering?

I'd recommend finding the GM digital service/wiring/emissions manual set online somewhere, and looking at the portion that discusses codes. I don't have access to any of my reference material, but I'm pretty sure the flowcharts have things like "CEL not illuminating" and what not. Understanding how the light is supposed to operate (on with key on, engine off, etc.) may help you better diagnose.
 
dyeager535 said:
Is it flashing in a controlled pattern, or does it look like its flickering?

I'd recommend finding the GM digital service/wiring/emissions manual set online somewhere, and looking at the portion that discusses codes. I don't have access to any of my reference material, but I'm pretty sure the flowcharts have things like "CEL not illuminating" and what not. Understanding how the light is supposed to operate (on with key on, engine off, etc.) may help you better diagnose.
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Everything I’ve read so far mentions nothing like this. It flickers randomly. The flickering is accompanied by stuttering in the engine when it’s running. I’m thinking it’s gotta be electrical somewhere.
 
It’s weird because the CEL will flash even if the key is just in the on position. I’ve been wiggling wires all day and haven’t found anything yet.
 
try wiggling the wires heading from the ALDL to the ECM?

remind me - does the SES flash appropriately if you try checking for codes?
 
Yes, if I jump the pins and turn the key on position it will flash 12 as expected.

After messing around with it last night I think there's a short in the the alarm system. I'm going to try to remove it completely from the loop and see if that resolves it.
 
Jumppr said:
Yes, if I jump the pins and turn the key on position it will flash 12 as expected.

After messing around with it last night I think there's a short in the the alarm system. I'm going to try to remove it completely from the loop and see if that resolves it.
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If something is sending strange voltage to the ECM somehow, I can see that causing issues for sure.
 
Well I removed the Hotwire from the alarm and it ran great long enough to get to the gas station. Half way home the lights started flashing again. Still not completely convinced it’s not the alarm though. It may have more wires somewhere causing problems.
 
I am thinking the aldl wires might be shorting. Give them a good look over.
Yep total alarm delete time. Repair the janky crap wiring splices from install
 
That thing doesn't have the GM security system does it? I want to think it was called VATS? Just a shot in the dark, I think that can cause issues when it stops working properly?
 
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