As far as I know no schematics exist for the CCMs (outside of GM). Also, 30-60 seconds, or 30-60 minutes?

That is so beyond cool. Way to go!!

Apologies for my imprecise language. You are correct--it's not really that the PCM/CCM are using metric units. It's that the way the human squishy bit interfaces with those units is given, by GM, in...

That's very strange indeed. All the code in the car itself uses metric measurements for temperatures, and I have confirmed via the ADX files for 1990-1996 that the equation never changed from 1990,...

I wanted to bring this post back to say that it's precisely correct. I was looking through my FSM while analyzing a totally separate system and stumbled onto this description of the FEDS security...

Interface board? I don't recall seeing such a thing on BATEE. As someone who also owns a 90 I'm quite curious.

Congrats on successfully swapping in the '91 CCM!

Hahaha, nah, she doesn't have a name yet and is arctic white. But every so often, yeah, she does do some weird shit.

Just fired it up yesterday to move it out of the driveway so I could work on...

Yeah, the trip going to 0.0 was totally expected. That's why I thought initially that I had somehow gotten into trip mode instead. Only to flip over and realize no, that was the normal odometer...

Hilariously during one of my team's races we did actually get affected by space weather--it made the datalogging we did pretty much unusable becaus the GPS coords were unreliable (the datalogger...

I haven't tried plugging in and asking it for a Mode 5 yet. I plan on doing that next. It started raining only a few minutes after I managed to get the battery in (which was why I was in such a hurry...

I've got a bizarre one for you.

So the past month I've been away from home due to family emergencies across the US. I've barely had any time to be with the car, so it just sat in the driveway....

DTC 81 is “Engine Configuration Mismatch,” and must have been added in 1994 when the diagnostic message protocol changed.

DTC 41 is “ECM Serial Data Loss” and indicates a lack of response to the...

Oh, you're right, 81 wasn't in the 90 definition. But I was more talking about the 92-93 CCM anyway. Interesting that in the older CCM, getting the 'wrong' bit on the reply would just make the CCM...

I would be down, if only because the fact that Rob Dahm has stuffed a stock PCM and entire throttle body into the fender of his rotary-swapped C5 drives me absolutely freaking bonkers. There is no...

Bingo!! Thanks so much, that completely clears everything up. So yes, electrically the F-body PCM is a 'bus master', while the Y-body is a 'bus slave'. In a situation where all devices on the line...

You are correct on the DTC thing, yes.

I don't believe you need to leave the resistor open. I think the timer only sets when you attempt to turn the key to run.

It's not wiring, no. The 1995 definition specifically says, and I quote:

"During start-up, the CCM requests and receives information from the PCM or ECM as long as a DTC 41 is not present. This...

This I am actually super curious about as well. The error about L98/LT5 exists in the 1990 CCM, but there is no bit in the ECM reply message specifying engine type. There is, however, mention that...

Again, it was never tested on a 92. You are the first person to attempt it. I think it's right but since I didn't have a 92 to test with there was no way to be sure.

It should work perfectly on a...

Thanks! Did you get a chance to check those resistance values? I know you've been pretty busy with this stuff over the past few days, so figure I'll just give a gentle reminder.

With the...

Okay so then yeah, it won't allow programming if it's in lockout, which would suggest that it won't allow read in lockout either. I do still wonder how reman facilities are doing what they do.
...

When I tested CCM comms in the car, I unplugged the blue connector from the PCM to remove it from the bus, and then unplugged the ignition PASSkey connector to remove the resistor from the circuit....

I was giving this some thought lately--the difference between the Y-body PCM and the F-body PCM. While code-wise, yes, there's the bit where the F-body is its own bus master...there may be an actual...

That's awesome! I wonder if 94-96 is the only one that doesn't do F0 messages when PASSkey is wrong. Maybe they enhanced the security in the 92-93 to require the ECM to be on the bus, but kept the...

I have an update!

I was able to run experiments on my '95, and have concluded that the security was likely beefed up after the 90-91 CCM, just as was suspected. While on a 90-91 you may be able to...