I have a 1985 2.8L v6 camaro. When I am driving the check engine light is always on. But when I try and jump the connectors on the ODB1 port nothing happens. I have even took it to a mechanic and he could not get the engine codes to show either. Could this be a bad ECU?

 

I just went through two reman ECU's in the last month, here is what I discovered from my own testing, and from info from members on here. Firstly, turn your key to the ON position and observe the check engine light. It should "bounce", or turn on and off quickly, then come on and stay illuminated. This is basically the initial check of proper ECU operation. If it doesn't do this, then right away you know something is preventing the check from being passed, although it doesn't necessarily mean the ecu is bad. You can check your ground strap from the back of one or both cylinder heads, and the main engine groend coming from the negative battery cable. Make sure those are good first. I can't help you much more wince you can't retrieve codes, but you could search the site for posts from Vader about ECU operation, he has multiple posts with a complete rundown of it's operation and testing.

 

I will go ahead an look at that tonight when I am off work and see if there is possibly a bad ground causing the issue and see how the ECU light comes on and I will reply back.

 

So when I put the key in the on position the check engine light comes on and stays on it does not flash or do anything like that. I did not have a chance to check all the grounds in the car yet though my neighbors needed help last night with their vehicle.

 

Do you have any driveability issues? Mine would run like a top and then die at will. As it got worse, the issues worsened until it finallyrefused to start. The absence of a bounce means it is failing the initial check and is likely bad. Pep boys has remans fairly cheap.

 

It is very difficult to start when it has been sitting over night but after like 10min or so of driving around and warming up it will no longer try and stall at a light and will be easy to start the next time. There are popping noises coming from my engine when it is in the warm up period. But I am afraid this may be related to a wiped cam lobe. But I suppose it could be related to the ECU.

 

It very well may be related. You can get all kinds of strange problems from a malfunctioning ecu. It could also be pinging when cold either because of using base tables or not advancing spark if in fact is it bad. If it's backfiring through the intake it's probably spark related anyhow. The hard initial start may be completely unrelated, sounds almost like a fuel system issue. Here are a few posts from Vader on ECM's, he really know his stuff about these and following his posts is what helped me track down and fix my issues.

I take no credit for these posts, they are from vader! Good luck tracking this down and post your results.


Steve,

The ECM is supposed to operate in this manner:

Install the key and turn the ignition to RUN (not start). The SES lamp should light briefly, turn off briefly, then relight and remain lit until the engine is running. This flash, or "SES Bounce", indicates the ECM has run and passed some rudimentary self-diagnostics, like scanning for a valid EPROM, scannig for valid firmware PROMS, an input voltage test, I/O test (to see if any loads are connected), and some other internal systems tests. If there is a problem during this test, the lamp will remain off or flash once and remain off, depending upon the type of problem.

When the ECM is placed in Field Service Mode, the electric fan will operate continuously.

It seems that you may have an issue with the ECM. The first thing to do is disconnect the battery ground, expose the ECM, open the EPROM cover, and reseat the EPROM in its socket. Next, you should disconnect each header plug, inspect the contacts for damage, then reconnect them. Repeat the disconnection and reconnection a couple of times, and the contacts will tend to wipe clean the traces on the circuit card or connection pins. While you're there, verify a good ground connection to the ECM, since that is crucial.

Reassemble the ECM in place but do not replace the covers just yet. Start teh engine and allow it to idle down normally. Once the engine is running, tap firmly on the ECM case with a couple of finger or lightweight screwdriver handle to see if any internal connections may be intermittent. If you detect a stumble, stall, or SES lamp as a result of the tapping, the ECM should come back out for further inspection.

Once that's accomplished, you may have solved your problems if the issue was poor connections from 15-year old contacts. Let's hope. If not, we're still here.
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Field Service Mode really shouldn't change any operational parameters, only monitor the fuel offsets and ECM feedback mode, and relay that information through the MIL lamp.

Field Service Mode

On the OBDI ECMs, you can jump 'A' and 'B' terminals on the ALDL while the engine is running.

WARNING! This must be done after the engine is running. This is called "Field Service Mode" and will not harm the ECM.

If the ECM is in Open-Loop mode, the SES light will flash rapidly, about 2½ times per second. If it's in Closed-Loop mode, it will flash about once per second. When in Closed Loop mode, flashing less than once per second indicates the ECM is enriching the mixture above the 128 count base line. Flashing more than once per second indicates the ECM is leaning the mixture below the 128 base line.

Backup Fuel Mode

A 3.9K resistor installed between ALDL terminals 'A' and 'B' forces the ECM into Backup Fuel mode. This mode forces the ECM to use predetermined fuel calculations in the ECM PROM instead of the learned inputs in active RAM. This is more commonly referred to as the "Limp Home" mode of operation. Backup fuel is usually around 12:1 or richer from the factory.

If your engine seems to run better in this mode, there is likely a sensor input that is reporting incorrect data to the ECM. Likely suspects are the oxygen sensor, CTS, and MAT sensor, but a MAP or MAF can skew the mixture as well.

 

Thanks for the info ravage. The reason I say the cam lobe may be flattened is because I did not have the valves not adjusted correctly because of my chilton did not give that a great of a method in adjusting them. I had replaced one cylinder head and had the other machined. The up and down method of moving the push rod worked like a charm though. It could be related to a fuel issue or spark though. The plugs are black with dry carbon like it is running rich or there is not enough spark. I think the spark is fine though. new spark plug wires, plugs, rotor, distributor cap, ignition coil, pickup coil, ICM. My ignition is new and if anything I think its a fuel problem or more likely a ECU issue since these odd things are occurring with it. I will take it apart after work and look in it to see if I see any damage and clean it.

 

I just replaced the ECU and it made a huge difference. My old one must have been damaged somehow or 28 years just took its toll. The car runs much much better than it did before. The check engine light flashes when I turn the key to the on-position. I really appreciate the help Ravage your awesome and so are the other people on this site who have gathered all this useful info.

 

So what if I say I never seen that light in my 1990 camaro rs vert does that mean I have a bad esu

 

Ecu

 

Ravage and Vader you sound the men for my question. I have a 89 TA GTA It has a 383 Stroker in it. I ran perfect for a year after I bought it. Lately it is idiling a little rough however the big issue is when you are giving throttle it misses really bad. The second you stop giving throttle it runs fine. I have tried replacing EVERYTHING from the MAP, TPS ICM, MAT you name it. I Have decide the ECM must be bad. It was reprogrammed by the motor builder who's name I do not know. VATS and EGR Have been unhooked. My main question is, Should I be able to get a replacement ECM and put my programmed EPROM in it without any issues?? It acts just like an old carburator excellerator pump when bad. Any ideas would be greatly appreciated. Thanks

 

Ravage and Vader you sound the men for my question. I have a 89 TA GTA It has a 383 Stroker in it. I ran perfect for a year after I bought it. Lately it is idiling a little rough however the big issue is when you are giving throttle it misses really bad. The second you stop giving throttle it runs fine. I have tried replacing EVERYTHING from the MAP, TPS ICM, MAT you name it. I Have decide the ECM must be bad. It was reprogrammed by the motor builder who's name I do not know. VATS and EGR Have been unhooked. My main question is, Should I be able to get a replacement ECM and put my programmed EPROM in it without any issues?? It acts just like an old carburator excellerator pump when bad. Any ideas would be greatly appreciated. Thanks
Darren1 is offline vBGarage Page Report Post

 

Does your "SES" light flicker on, then off quickly, then off again when you tuen your key to the ON position? Do you get code 12 when attempting to retrieve codes? IF both of those check out, chances are it is operating properly. Sounds more like you need to check the ignition and fuel systems to me. Check for vacuum leaks as well. Nothing worse than replacing parts that don't need to be replaced.

 

Thanks for responding. I installed a fuel pressure gauge at the fuel rail and I have excellent pressure. I replaced the cap and rotor also plugs. Also I tried a spark control module off a camero that runs great with no difference. I have ECM out of car now so no I have not checked for the flashing engine light. I will have to reinstall and check that. I do not remember the code number but it showed I had a ignition spark issue which is why I tried to other spark box controller. Still scratching head but will hook ECM and check for the flashing light. Do the EPROM's go bad or can I stick my programmed EPROM in a new ECM with good results?
Thanks again.