Error code 43

I have a 1993 Lumina with the 3.1L V-6.

I bought it used, and have changed the EGR and MAP sensors and have given the engine a thorough de-carboning with seafoam. About two weeks ago, I had a CEL come on, and found it to be a code 43-Electronic Sensor malfunction. My only problem is, I've heard that MANY things can cause this: clogged fuel filters, arcing spark plug wires, even a defective ignition coil. The strange thing is, the CEL doesn't come on unless I drive for awhile at sustained highway speeds-it will then drive rough and stumble before the light shuts off on it's own.

I've noticed the Lumina has run pretty rough off and on; little or no throttle response at times since this CEL went on. There's also a horrible rotten egg smell coming from the exhaust, but the car passed emissions last month with flying colors. Since this car sat for awhile and had evidently little maintenence (the prior owner went into a nursing home), it is time to swap out the coil and plug wires anyway?

Rotten egg smell is the Cat if i remember correctly (IIRC)

might want to get that replace, also check your fuel filter, make sure it is not clogged. do a fuel pressure test, also check the vacuum hoses.

I figured the cat would be the cause of the rotten egg smell, but it passed emissions without any issues; MA now has CA emissions, so they are jerks about any of that stuff.

Code 43 is electronic spark control fault. This could be caused by three things.

1. Bad ignition module or corroded terminals on it's wiring harness.
2. Bad crank sensor(s) or corroded harness(s)
3. Bad computer or corrosion at the computer harness

All three would be affected by underhood heat, so each would worsen on a long drive due to higher underhood temperatures. I listed them in order of probability. The crank sensor is the cheapest, followed by the computer, and the ignition module is the most expensive. Also, if the GM service number on your computer is 1227727, there is a good chance it is bad, as that particular number has a much higher failure rate than other GM ECM's. The rotten egg smell is from all the unburnt fuel due to the spark problem getting into the exhaust and overwhelming the catalytic converter.

Thanks Rich!!

What would you suggest my plan of attack be?

Should I just check the coil and replace first (I'm assuming the ignition module is the one on the front of the motor- facing the radiator under the valve cover) and then the crank sensor? I planned on changing it anyway, as this car has evidently been sitting for awhile...

Anything else you could think of to fix as well??

thanks again!!

Thanks Rich!!

What would you suggest my plan of attack be?

Should I just check the coil and replace first (I'm assuming the ignition module is the one on the front of the motor- facing the radiator under the valve cover) and then the crank sensor? I planned on changing it anyway, as this car has evidently been sitting for awhile...

Anything else you could think of to fix as well??

thanks again!!


What do you think of replaceing the module? i was also thinking of "heat sink" issues with the DIS module itself...

Any thoughts on where to pick up a new ignition module cheap?? The cheapest I can find is 79.99 at Autozone....