I have a problem with my PCM and need to replace it.
I have an intermittent code 22, which I've traced to the 5V PCM output for the TPS having no voltage intermittently.
Car is a 1994 Camaro LT1 M6.

My question is, exactly what do I need to do when I get the replacement PCM?
Does it need to be flashed to my VIN so that the pass-key will work?
If I get an ALDL cable, what software do I need?

I would rather get a cable and software to do it myself than take it to a dealer. Plus I'd like to be able to do tuning in the future.

Thanks...

 

Tuner Cat or LT1 edit is what your going to use to tune with. THere both good programs to use. As far as PCM swapping, dont worry about it as long as it came from an obd1 fbody or b-body you should be fine. Once you have both you can throw in a m6 or an a4 program of your choice.

 

The computer does not care about VIN for Pass-Key. It merely gets a signal from the theft deterrent module.

 

Thanks for the help guys, you're awesome!

One other question...
Where will I get the m6 program to flash to the new PCM? Does that come with the software, from the old PCM, or do I download it?

Thanks again!

 

It'll be easiest to get the program from your old PCM.

Have you checked the TPS signal wire for a bad ground?

 

Why do you assume this is a PCM problem. Unless I am misunderstanding what you posted, it sounds more like the TPS is bad, or something in the wiring.

Rich

 

I have tried two new TPS sensors, but that hasn't changed anything. I also confirmed that both are working correctly with an ohmeter.

I have confirmed that all 3 of the wires from the TPS to the PCM (signal ground, 5V supply, and TPS signal) are not shorted to ground, and have zero resistance between the TPS connector and PCM connector. In other words there are no shorts or breaks in the wires.

When the car was having the problem, the 5V supply for the TPS circuit had no voltage. When the problem went away, the 5V supply was working normally, and the TPS resistance was in the correct range (~0.6 at idle). I also checked the MAP and IAT circuits to make sure my check method was correct, and they were working normally the whole time with 5V on their circuits.

Again, the problem is intermittent. I'm not sure what's causing the TPS supply voltage to drop out, but it seems to be internal to the PCM.

Let me know if you have any ideas for other things I should check.

Thanks...

 

So, can I upload the program from the old pcm using tunercat or lt1edit?

Thanks again for your help...

 

How and where were you measuring the +5V reference signal from the PCM?

 

what u should do is get a scan tool and stop guessin bud.all of your tests are in vain.back probe your signal & ground your other lead, w/koeo set ur meter to volts.closed throttle should be 0.4-0.7v open throttle slowly and check 4 spikes or drop in reding.WOT should be 4.5-4.9v.this is kinda innacurate.u need a o-scope or a scantool.b4 u buy a new pcm atleast have somone run a pcm onboard diagnostic check(scan tool)then u will know if pcm is shot

 

I have already checked the TPS signal voltage by back-probing. Sorry I mis-spoke in my previous reply, I meant that it was 0.6V at closed throttle.
I am checking the black (signal ground), gray (5V), and blue (signal) wires for the TPS circuit at the PCM. The 5V across the gray and black wires is dropping out intermittently, which also makes the TPS signal drop to zero. The sensor itself is working fine and has the correct voltage range as long as there is 5V supply.
I don't have acess to a scan tool, although I'm not sure what else that would tell me on an intermittent voltage problem. Please explain if it could verify the source of an intermittent sensor voltage supply problem.
Is there anyone in central OH with an OBD-I scantool that could help me out?

 

If you're wanting to get into flashing your own stuff anyway and tuning, you have to have a laptop for the LT1 Edit or Tunercat sw and the needed cables. So why not just get DataMaster or other laptop scan tool why your at it. Then buy another PCM...if it turns out the problem is not the PCM and it continues, then you have yourself a spare PCM for when the communications drop in the middle of flashing and the PCM is rendered usless until you can pull the chips and physically have them reburned.

You can probably get all of the needed software/hardware for the price it will cost you to have the dealer reflash a PCM anyway
I bet the problem is in the wiring somewhere and only does it when its bounced around due to a bare wire somewhere or a loose pin on the harness connector to the PCM...I've had that prob before.

 

Thanks for the help 2quik6.
I have a laptop, and have been considering getting a USB to ALDL cable from aldlcable.com for $65. It looks like LT1Edit is $200 and Tunercat is $90 with the ECM definition file. Unless there are some significant advantages to LT1Edit, Tunercat seems like the way to go.
The local Chevy dealer says they will flash the replacement PCM for $60.

I thought it might be a loose wire too, but I was measuring the voltage at the PCM across the gray and black wires and it was zero. Then it suddenly came back to 5V without anything else changing. This is all while sitting in the garage. While driving, sometimes it's ok, sometimes it's not. No rhyme or reason that I have noticed. All of the pins looked ok and set when I pulled the connectors off of the PCM to check.

The only other options I can think of are to try splicing new wire in between the TPS and PCM, or connecting the TPS 5V supply to one of the other 5V supply wires that I can verify is working correctly. That seems like a bad idea though...

 

Just thought I'd post the outcome of all this...
So, I ended up replacing the PCM with a reman from Advance. Bought a USB to ALDL cable from aldlcable.com, and Tunercat, and downloaded Datamaster.
Tunercat worked great for reading the data from the stock PCM and flashing the new one.
Unfortunately, the PCM wasn't the problem. Using Datamaster, I was able to see that when my TPS voltage was dropping to zero, that the MAP signal and A/C Pressure switch signal were also dropping out, and the car was setting codes 22, 34, and 66.
TPS uses B28 for 5V. MAP, A/C Pressure, and A/C Evap Temp all use B29, and B28 and B29 are linked in the PCM (according to the Serv. Manual). With the VOM, I was finally able to track down that the 5V gray wire for the MAP sensor was shorted to ground somewhere between the PCM and the sensor. But it was only causing the problem when the engine was warm.
Anyway, after running a new 5V supply wire from the PCM to MAP sensor, and also splicing it in to supply the A/C pressure and evap temp sensors, all is good again.
I haven't pulled the original 5V MAP wire out yet to see exactly where the problem was, but hopefully there aren't any other problems that will surface later.
I'm out the price of the reman PCM, but if I hadn't done that I probably wouldn't have bought the cable and Tunercat, and now I'm having fun with that!
Thanks for everyone's help...

 

want to sell the PCM you pulled out? put it up in the classifieds