1988 Codes 33 and 36 Help!
 

Well, I've followed the factory service manual, checked all the connections, followed all the procedures for both 33 and 36 but one thing confuses me. Diagnosing code 33, it would appear I need to replace the MAF sensor. But when I get to code 36, it says "A faulty MAF sensor should not be considered as the cause if a code 36 is set" Following all the diagnostics to the end of code 36, it says it could be a faulty ECM. Is there any way to test the ECM or the MAF sensor? Help!

....you sure the relays behind the battery are ok?...had a similar problem and changed out both and problem disappeared....as far as testing the ecm - can't help ya there but, if the car runs crappy with the maf connected, pull off the connector and if it "smooths out", chances are the maf is "kaput" (only after checking the aforementioned relays 9both are same and same number, about $12.00/apiece.....

Code 33 Problems
 

CODE 33 PROBLEMS

There are a few things that can cause a code 33 which is a high MAF signal. These could include a) an open wire or terminal at or to the MAF; b) faulty relays (or installed backwards and with this I mean there are two different relays used one for power and the other for burn off, and if they are switched I have seen them give code 33, don't know why but I have seen this even though they seem to be the same relay with the exception that one comes with a shock absorbing strap and the other one does not so one thing can be to just swap relays and see if that helps). Relays could be a good possibility and would be worth checking and you also need to try swapping them to make sure they are not the problem.; c) faulty MAF sensor and the last possibility being; d) the ECM.

PROME REVISION - I want to point out that Chevrolet has come out with a revised PROM for the 1986 Corvette due to code 33 problems. Now before you go off and order the revised PROM we need to find out a little bit more of the problem you are having. This is not a hard code to fix but you may have to do a little looking.

WIRING - Wiring is not a common code 33 problem but if you have an intermittent problem that could be a sign of a poor connection of one of the terminals at the MAF sensor. If the light comes on right away that could also be a sign of a broken wire. If one of the MAF sensor wires becomes open it will set a code 33 but, this condition would happen all the time probable shortly after start up. If you have access to a scan tool I would hook it up and read the airflow; when warm it should be around 6.0 grams per second. Then try wiggling the wires and if it shoots up you having a wiring problem. If it's high all the time then you could have an opening in the wiring. I would suspect that seeing how you tried a new sensor that would not be the problem but I would check it anyway to begin with.

ECM Upgrade - I suspect that you have a #1227165 ECM in the car and that could be the problem. This is the original style ECM used in the 86 to 89 Corvettes. Chevrolet has had a real problem with the internal circuit board cracking on these original units and when this happens there can be all kinds of problems including code 33, 36, 34, 15, 51 and a few more. Drop down the ECM and see what the service number of the unit is and if it's a #1227165 replace it, if it's an aftermarket rebuilt painted black one replace it as I do not trust that old style ECM at all and I have found that just about all aftermarket replacement ECM units are of the old style. The GM number you need to go back in the car with is a #16198259 it is the GM replacement for the original #1227165 and is much better.

Had the same issues one time.
Just buy the two new relays, replace them and remove your battery cable to clear the codes and see how it goes.
It will probably fix you right up unless you have a bad MAF or wiring issue.

:cheers:

Thanks everybody for your help and insight - I REALLY appreciate it :cheers:

As it turns out it was the MAF sensor.

pmihaltian, thanks for the replacement ECM part number. I'll keep that number on hand for when the day comes that I need to replace it. One question on the upgraded ECM, in addition to the improved circuit board, would there be any performance improvement as well?

Thanks again for taking the time to help me.

Greg

I had the same problems, replaced the MAF power and burn off relays and never has the codes again. I was getting intermittent 33 codes.