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So I was driving around today and my CEL lit up for about 30 seconds then shut off. Then as I was coming home it came on and stayed on.

According to this chart: ECU Trouble Codes the problem is the A/F Learning Control.


Ok. So now I know what the problem is, but how do I fix it?[/url]

Which car, the 91 or 93?

The learning control is really a function of the ECU. I'd try resetting the ECU, and if it continues I'd double check all the sensor connections, and if tha doesn't do anything, swap out the ECU for another.

Are you having any symptoms?

Oops. It's on the 91 SS.

On my way to my friends house the light popped on for about five minutes and then turned off again.

It didn't come back at all on the drive home.


The car hasn't been acting funny at all. It still drives great. The only weird thing was the CEL.

Hmmm so I swapped out the ECU with another one that I had lying around and I'm still getting the same problem.


So what could be the problem? What sensor connections do I need to check? Could a vacuum leak cause this?

I decided to check the codes again and I'm still getting the Code 41 along with Code 45 which is the atmospheric pressure sensor...

Code 45 is the pressure sensor and pressure exchange solenoid valve

Not sure what to tell you about code 41.

Hmmm. I am running one of Vikash's FCDs. I know that I had to tap into the pressure sensor and exchange solenoid valve to install it, but I've had that installed for almost six months now. Seems funny that it would just start acting up...

Any thoughts or ideas from anyone else? The light comes on for awhile and then once I start driving for a bit it'll go away. Occasionally it will still come back on after it's already gone off..

Ok. So I installed the third ECU I had lying around because I was told that there's an atmospheric pressure sensor in it. Voila! The code 45 went away, BUT the code 41 for the A/F Learning Control continues to pop up!

What the heck?! This is frustrating...

Lol so anyone want to help? I could really use it.

Is it bad to drive the car even though its A/F Learning Control isn't working properly? The car seems to run fine...

Where does the ECU get it's A/F ratio information???

O2 sensor.... I'd start there.

I was going to do that, but I replaced my O2 sensor about a year ago. Do they really go bad that quickly?!

I haven't had one go bad yet (Knock on wood), but I did have to replace the one on my White wagone when I got it because the wires were torn out. I'd try a used one first and see what it does.

I had a van that would throw an O2 code only on the highway, was fine around town. I suspect it was reading on the ragged edge of lean, adn th elight cruise pushed it over the edge.

Problem Solved!


So before spending $150 on a new O2 sensor, I thought about what else controls the A/F mixture. Instantly I ran to my car and pulled off my air filter and MAF. The MAF was covered in oil.

I used some MAF Cleaner on it, plugged it in and voila! No more code!

nice work, weird how the maf would do that, makes sense though, where do you get maf cleaner?

They have it at the autostore. Make sure you get one that's lubricant free. Typically an electrical contact cleaner works pretty good as long as can states it leaves no residue.

Rubbing alcohol works too.