1994 z28 ses codes I can't figure out to fix problem

[Z-28_collector]

i have a 1994 camaro z28 and just borrowed a scanner from a buddy and i have scanned and got these codes can anyone make sense of what the main problem might be?

dtc 42,43,44,45,51,53,54,55

Runs and drives the alternator is putting out 14v while charging and battery was tested with showing 12.50v and running 13-14v tested all grounds in engine bay, all fuses, and power terminals all checks out. Do I just have a bad PCM?

[94Blackbird]

It's likely since that 51 is an EEPROM program error code.

[Z-28_collector]

I have tried everything else and it still runs and drives would the code 51 still let that happen?

[Injuneer]

I think I've seen this same post on another site. It was suggested that the DTC 53 for high system voltage, if accurate, could be causing codes on the voltage dependent items. Did you check for high voltage at the PCM? It would have to be an intermittent problem - always hard to find.

If you clear the codes, how quickly do they come back?

It was also noted that DTC 54 is not a valid code for a 94 F-Body, but it is valid for a 94 Y-Body with the OBD-1.5 PCM.

[Z-28_collector]

yes I did post on another form site, im just so frustrated about this electrical problem. so with that said to answer your questions, yes I disconnect the battery for 30 mins and pull fuse and codes will not clear they come back as soon as I hit the key switch. I have checked all the ground and power supplies in the engine bay top to bottom and they all check out. I did have a time when pulling codes it showed nothing, and other times it would just pull a trans circuit code. I have not checked the power supplied coming from the PCM could you explain on how to find the right circuit for that? and yes I am pulling that 54 code on and off and I know that's not for fbody so im wondering if someone thought they cold just swap PCMs without programing to the cars vin and parameters . I just bought this car a few weeks ago and its real clean top to bottom other than that issue, so I could not vouch for the previous repair history of it other than the owner did not know a wrench from a screw driver lol. thanks for replying and helping me figure this out.

[bobdec]

Sounds like car has been doing this since you got it a few weeks ago. You said .." pull fuse and codes will not clear they come back as soon as I hit the key switch" Are we saying with just key on w/o engine running the PCM is posting codes for a Y-Body (DTC 54), and a DTC 44 which requires engine running in closed loop for 50 seconds. Also DTC 53 requires voltage at 17.1 volts and the engine running. Way to many invalid things happening, you either have incorrect/corrupted PCM code, or your scanner is not reading correct. It's not impossible, but it's hard to see, a defective PCM allowing engine to run perfectly and still be so confused. If you had a laptop, $50.00 cable and free software, DataMaster-20 free logs, Scan9495 or Freescan resolving this would be a lot faster.

[Z-28_collector]

yea im going to by a an adapter for the serial port on my scanner. but yea its pulling a DTC 54 and it comes on with the key on engine off even when i try to pull fuse to reset but code does come on right way. i think either its not the right pcm or pcm is fried. and it required 17.1 volts for operation? or is 17 to much voltage because the scanner was telling me the pcm was getting to much current.

[Z-28_collector]

the 54 code thats not suppose to be in there i herd from people on here and other site that they came in the Y body PCMs but just to let people know i tested all the PCM pig tails with my power probe 3 and red,blk,blue, and clear all were good and no breaks in the circuity on that end and all the grounds and power supplies were good, so i think the culprit here is the PCM it self i think its not throwing the correct voltage out to all the sensors and causing current spikes and lows. causing all the codes. or it might be an y body computer all together. so any suggestions or commits on my reasoning let me know. i can all way appreciate many other brains than just mine.

[Injuneer]

Easiest check would be the knock sensor (DTC 43). Key on/engine off, harness connector off the sensor, see if you have 5V when measured between the single dark blue wire in the connector and a good/clean ground on the engine block.

Another odd thing - DTC 55 can't set if DTC 44 or 45 is set.

What scanner - make and model - are you using?

[Z-28_collector]

i have a 1994 camaro z28 and i used a innova obd1 scanner and the check engine light automatically comes on i have swapped pcms with my daily driver and still same result so its somewhere in the wiring. i will check the knock sensor tomorrow on the lift. so could that be the main cause in the wiring loom?

[Injuneer]

You are looking for symptoms that set codes. If the KS voltage goes over 4.1 it sets DTC 43. Since the PCM is supposed to be supplying a regulated 5.0V (and the KS pulls it down to about 2.5V), it's remotely possible the PCM voltage regulation is screwed up. That would show up as more than 5V on the harness wire.

What do you mean when you indicate "the check engine light automatically comes on"?

[Z-28_collector]

when i turn the key on to the on position it will automatically light up with no delay so i have swapped pcms from my daily driver and same result so it has to be a component in the wiring harness but i cant figure out where to start with it. im going to put it on the rack later and check all wires underneath the car again for shorted or cut wires. but im trying to figure out what componet in the car engine bay would set off all the codes do they all run off eachother? could it be my optispark.ICM?

[Z-28_collector]

i think it just might be the wrong scanner im using can someone recommend a good one besides a cable. i found someone was having the same problem with the innova scanner just as i have with the same codes and pulling 3.8L codes as well

[Injuneer]

Here's someone else on CamaroZ28.com who has a very similar problem, and is using the Innova.

http://www.camaroz28.com/forums/lt1-based-engine-tech-9/cant-erase-trouble-codes-94-z28-875259/