Possibly the ECM

[Intruder]

Hi guys, a noob here. Got a tough one here. This may take a while...
Got a 94 Camaro coupe, had it since new. Freeze plug went bad and so my uncle and I had to pull the starter, exhaust and motor mount to replace the one on the passenger side. While reinstalling the starter he grounded the ingnition terminal and the batter terminal on the solenoind against one another. Now to the problem.

Right off the bat I noticed the ABS and airbag lights remained on and never drove it. The car sat up for a while and recently I began a bit of a restoration attempt. I have come to realize that of the relays under the hood are working. I realized this because the fan will not work.

I replaced temp sensor & sending unit. Tested the fan motor. Tested the fusable links at the block underhood. At the suggestion of a GM tech I replaced the ignition switch which was not bad.

I have a Haynes manual but they do not have a diamgram for the ignition or ecm.

I suspected the ECM/PCM was bad but the GM tech said that it is unlikely because the car will run. However; the OBDII can not comunicate with the vehicle. I have also by passed the Passkey 2 system due to a bad lock cylinder.

I have constant power to the relay block but no switchable power. And all the fuses and relays test good.

If anyone can solve this enigma, I will send you a case of your favorite beverage (yes, even adult beverage as long as you are drinking age). HELP!!!

PS
I had the remaining freeze plugs replaced. The shop that pulled the tranny to do the ones in the back of the block said they found rodent droppings in the under carriage. We have lots of squirrels, so I traced the wiring under the car as best I could and found no immediate signs of chewed wires. Food for thought.

[Injuneer]

Right off the bat I noticed the ABS and airbag lights remained on and never drove it.

Not connected to the main PCM, they each have their own computer.

I have a Haynes manual but they do not have a diamgram for the ignition or ecm.

Shoebox has the wiring diagrams for his 95 on his website. You 94 is virtually identical, except for a couple fuse assignments.

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_wiring

I suspected the ECM/PCM was bad but the GM tech said that it is unlikely because the car will run. However; the OBDII can not comunicate with the vehicle. I have also by passed the Passkey 2 system due to a bad lock cylinder.

Find a new "GM Tech", and get a new scanner..... your 94 has a 12-pin ALDL connector, and is OBD-I.

[Intruder]

2 out of 4

I have managed to clear up all the issues with the exception of no air bags cooling fan or AC.(And the cooling fan and AC should be one in the same problem)
I have not located an OBD1 as of yet. I did however try to "jump" pins a&b in the OBD1 port which should have fired the fan through the pcm. No luck.

Thanks for your help, any other advice would be greatly appreciated.

[Intruder]

Mystery solved... I think?

I got the scanner to work, I reset the ICM and that took care of the security light and suddenly the scanner communicated with the PCM.

Still the air bag system and the cooling fan/A/C would not work. The scanner indicated that the A/C clutch had been disabled, so I read the line pressure on the scanner, 7 lbs. Shot in a can of refrig with sealer and oil. As soon as the line pressure hit 20 lbs. cooling fan and A/C kicked right in. So the GM tech was correct, problem was not PCM, yet just a pile of minor issues that seemed to take forever to identify.

Now can anyone tell my WHY GM would design the cooling system and AC to be dependent upon one another?

I did get very high temp reading from the gauge in the dash, but the scanner read a much lower temp and when the scanner read 225 the fan kicked in. I have replaced the sending unit... so I believe I have a bad gauge. So now I have an excuse to install pod gauges! LOL. Not unless someone can give me some other solution or plausable explaination.

Thanks for all your input and help guys!

[Injuneer]

Which coolant temp sensor did you replace? The gauge is driven off the one in the driver's side head, the PCM gets its signal from the one in the water pump. The 1st fan (or low speed, depending on when your 94 was built) is programmed to turn on at 225*f, the 2nd fan (or high speed) at 236*F.

The air bag system has its own controller and isn't tied into the PCM. Its called the DERM module. The fact the light is on could be indicating that an airbag harness connector is disconnected, the airbag is defective or one of the sensors is not functioning. You need a special scanner (e.g. OTC Tech II) to read the DERM module.

What do you mean by " I reset the ICM"? What does the ignition comtrol module have to do with the security light?

[Intruder]

Possibly the ECM

I replaced both the sensor and the sending along with the relay... because I was getting such a high reading on the gauge I would shut the car off hence not allowing it to reach a high enough temp to fire the fan relay. I have a universal manual temp gauge I plan to use as a tester along with the scanner to make sure the PCM is reading correctly.

As for the security system and the ICM, the security light would not extinguish after I replaced the lock cylinder. I then pulled the ICM fuse, switched on and then off again. Put the fuse back in and low and behold the security functions properly now... I even tried to use the blank key that came with the cylinder, no start. Put the chip key in and it fired right up. I do not know how or why but that is what happened.

Also where I got a message that the scanner "can not comunicate with the vehicle" suddenly gone. Now it works fine.