My code 36 won't go away on my '88 IROC. I've done the troubleshooting as instructed by the GM service manual. On the step where I ground CKT 900 (black wire), I use a test light and the test light is dim when I back probe the MAF burnoff, when i poke the black wire just before the relay, and when I poke the black wire (CKT 900) just outside the ECM connection (D12).

The test light burns bright on anything "hot" like the battery or whatever cicuit is "always hot." I've used an analog voltmeter to measure voltage. "Hot" wires show 12 volts. CKT 900 shows less at about 10 volts.

I've already replaced the oil pressure switch, all of the relays (MAF power, MAF burnoff relay, fuel pump relay, fan relays), the ECM, and still code 36 returns. My connection at the MAF sensor appears to be good, but I have a new MAF senor harness with connector just in case. I've read the the MAF is usually not the cause of code 36. So, is it a bad ground somewhere? Anyone who has had this problem, where did you look to solve the problem if replacing the relays didn't correct code 36?

 

Just looked at my service manual and according to what im seeing ckt 900 is a ground for the maf sensor that the ECM controls. If your seeing voltage at all on that ckt you found your problem. Somewhere your shorted to another wire carring voltage. Check your wiring harness for a pair of wires touching that shouldnt be. If you already found the short and seperated the wires and still have a code 36 the ECM may be fried. Good luck.

 

If your seeing voltage on the ground side it could be a poor ground. Now I haven't looked at the wiring diagram so I'm assuming it's been described correctly here. If the ECM supplies this ground and your checking the circuit after the load there should be no voltage. So you have one of just a few issues here.

884+3's theory that there is a short, unlikely in my experience but possible.

The ECM has a poor ground and is unable to ground the circuit.

Resistance in the circuit. Somewhere between the MAF and the ECM

Or the ECM has an internal fault

All voltage should be used up at the load. If not there is a secondary load on the circuit somewhere the requires the voltage. It's Ohm's law, I understand it but can't explain it well.

I hope this makes sense, and helps.

 

So the new (rebuilt) ECM I put in could be no good due to a short?

I guess I'll go and look at every ground and see if there's corrosion or look for broken wires touching each other. Thanks.

 

Don't be so quick to condemn the ECM. I've almost never had one bad when other people say they were "bad". The only tiem I can recall is when an external load shorts and the fuse protection had been tampered with, or the system voltage went crazy high, causing crispy components:



Do you have both the MAF power and burnoff relays replaced? Corrosion in either (or the connector sockets) can result in a partial short, providing power to circuits that should not have it.

 

I did replace the MAF power and burnoff relays and checked for corrosion in both. No corrosion in the connector sockets. I still get code 36 everytime I start the car.

I checked the grounds that I could see from the top of the engine bay and all were tight. I noticed that in the "1988 Camaro Electrical Diagnosis Service Manual Supplement" there is a ground called "S143." It's a ground for the ECM, Fan pressure switch, MAF relay, fuel pump relay, gear selector switch. S143 ground is supposed to be where the heater hoses connect to the firewall. I looked really hard since it was difficult to see back there and behind the block. All I see is a braided ground strap. Do you know where it is? Or am I looking somewhere that is irrelevant?

It seems that no one on this site has had a code 36 problem that won't go away.

 

I dont have a ground distribution diagram but if memory serves correctly there should be three or four ground wires attached to the stud holding the air pipe for the cat. If theyre not there check the back of the drivers side head for them. You did disconnect the battery cable for a minute or two to clear the codes from memory. Sorry had to ask.

 

What you can do so as not to chase your tail also is one of two simple tests on the ground circuit. Check resistance on the ground circuit. Simply unplug the ECM and check resistance from the ground leads back to the battery or block. The other way is voltage drop, this is how Ford prefers we check this stuff. Keep the ECM plugged in and with it powered up check from the back of the pin to the battery or block with the volt meter on 12v scale. If you read voltage than you have a poor ground and need to go further. Neither test will pinpoint it but they can eliminate or confirm this is the issue.

I hope that helps

Dave

 

You should have a group of grounds coming out of the wiring harness directly behind both heads on ring terminals bolted to the head.

"S" denotes a splice & "G" denotes a ground ( VIN specific: )
Splice S125: Engine Harness, Top LH Rear Of Engine
Splice S143 (VIN F): Engine Harness, RH Side Of Dash
Splice S145 (VIN E): Engine Harness, Above Rear Of Engine
Splice S145 (VIN F): Engine Harness, Above LH Rear Of Engine

The above splices are connected to ground at:
Ground G112 (VIN F): Rear Of LH Cylinder Head
Ground G118 (VIN F): Rear Of RH Cylinder Head

 

Yes, I did clear the codes each time. I have to clear it each time I drive the car. Once it's cleared, the car drives fine.

Thanks, I'll go looking behind the engine or from underneath and see if there are any loose wires or broken ones.

 

Yesterday, I tried to find the grounds on the rear of the heads (firewall side). I looked from underneath and from the top. Very difficult to see even with lights and mirrors. Was anyone able to get to these without removing a lot of things? I didn't remove anything except the entire distributor assembly. I still wasn't able to see back there. Is it better to remove the right valve cover and A.I.R. system? I still have a fully functional air condition system, so I will avoid removing that on the firewall.

 

The valve covers is the most you'd need to remove. But, as Mstrtch said you'll really need to do continuity test from the unplugged connectors to ground to isolate which side of the engine harness to repair.