Corvette CCM Reverse Engineering Anyone?

[steveo]

i found another corvette enthusiast that i've been helping out too, so we have another dump coming.
would it be helpful if we had RPO sheets for any of these to do some feature association? might help figure out a few config flags? or are we already way past that

[kur4o]

i found another corvette enthusiast that i've been helping out too, so we have another dump coming.
would it be helpful if we had RPO sheets for any of these to do some feature association? might help figure out a few config flags? or are we already way past that

I can get rpo codes from vin stored in the file, so it won`t be an issue if there is a need to see the options.

[spfautsch]

I think it's a little soon to say, but here's what I'm basing the two option bytes on, from the A297.DS file:

..PAGE
..HEAD02L CCM ALDL DATA LIST 
..HEAD03L NUMBER OF DATA WORDS - 23
..HEAD04L CCM ALDL MODE 1 DATA LIST (MESSAGE 1)
 BYTE  BIT  DESCRIPTION
 ----  ---  -----------
 1          FIRST PROM ID WORD (MSB)
 2          SECOND PROM ID WORD (LSB)
 3-19       VEHICLE IDENTIFICATION NUMBER

 20    0    REAL TIME DAMPING          0 = NO        1 = YES
       1    ANTI-LOCK BRAKES           0 = NO        1 = YES
       2    ELECTRONIC THROTTLE CONTROL              1 = YES
       3    RESERVE FUEL INDICATION    0 = NO        1 = YES
       4    OVERSPEED WARNING          0 = YES       1 = NO
       5    SPEEDOMETER BIASING        0 = YES       1 = NO
       6    ROUGH ROAD DETECTION       0 = NO        1 = YES
       7    NOT USED

 21    0    ENGINE                     0 = LT1       1 = LT5
       1    TRANSMISSION               0 = AUTO      1 = MANUAL
       2    MAGNETIC SPEED-DEPENDANT VARIABLE ASSIT  1 = PRESENT
       3    HVAC                       0 = C60       1 = C68
       4    LOW TIRE PRESSURE WARINING SYSTEM        1 = PRESENT
       5    SELECTIVE RIDE SYSTEM                    1 = PRESENT
       6    POWER SEAT, DIRVER SIDE                  1 = PRESENT
       7    POWER SEAT, PASSENGER SIDE               1 = PRESENT

 22    0    NOT USED
       1    NOT USED
       2    NOT USED
       3    NOT USED
       4-7  NOT USED

 23    0-7  NOT USED

Bytes 20 and 21 match $b6c6-$b6c8 pretty much exactly. The only "mainstream" head scratcher is the C68 option which seems like was standard equipment after 90 or 92. Everything else that was optionally available before 97 was incredibly rare save the FX3 (selective ride system). NomakeWan's 94 has this and the bit's cleared on the dump he posted. I have a message out to someone with a 92 ZR-1 with the FX3, but he would need hand-holding and his wife is in the hospital with cancer / chemo + covid so I think I'm going to leave him to be with his wife for the moment.

Everything else was either not available, or doesn't make any difference to the unit.

Real time damping wasn't an option until much later afaik.
ABS might have been a delete-able option but would have been a special order
ETC didn't come into the picture until the LS1 in 97
Bits 4-6 are all 1s in everything we have

In byte 21 the engine option was pretty obvious. I think this one is probably the most complained about fault code with a mis-configured ccm.
Transmission seems documented well enough
Electric power steering was also not available until 200?
C68 versus manual A/C controls is still a grey area, but I think not relevant to the function of the module since all our cars have it but none have this bit set
TPMS was a very rare option so may have some bearing on things - good luck finding someone with that option
FX3 seems to not have bearing on the ccm function
The power seat options are irrelevant because there are no inputs / outputs it could possibly effect

I'm still open to discussion on how to handle the reman pin location and whether to include (odometer) in the .xdf. An "experimental" version is attached.

[steveo]

this is really awesome. nobody hacks body control modules.

for the reman pin i would not think its dirtier information than anything else we do with these modules. im in a country where reverse engineering for repair purposes is legal. totally your find and your call. but if you are that worried maybe just start really detailed rumors and let someone else do it.

if the general cared that much they would have put some proper protection on it.

my main concern is scumbags rolling odos back

[steveo]

speaking of odometers, i see you managed to wipe it, but did you actually decipher it? if not, i'd like to help with that too, give me what you've found so far ? i enjoy code breaking this old stuff

[spfautsch]

speaking of odometers, i see you managed to wipe it, but did you actually decipher it? if not, i'd like to help with that too, give me what you've found so far ? i enjoy code breaking this old stuff

What I've found is pretty much contained here. PM me if you want a more intelligent explanation, sometimes I omit very important details when I'm excited from cracking 30 year old engineering.

my main concern is scumbags rolling odos back

Edit: Me also, but keep in mind you have to take 1/3 of the interior apart to remove this module. It's slightly easier than pulling the engine and just a bit more difficult than replacing all four wheel bearing hubs in an afternoon. (end edit)

I have no idea where this could go. If you look on ebay the ccms that are there all have the mileage stated as if it's some measure of value. Personally I would like to keep mine correct to wear as a badge of courage. But who knows if the run-of-the-mill C4s will ever come to be coveted by car collectors. Plastic and unreliable electronics considered.

I'm posting this for those who understand the protocol. Please don't post a public dissertation about how I accomplished it if you figure it out.

TX+F15605B4
RX+F1570500B3
TX+F15A040020002071
RX+F15604B5
TX+F15605B4
RX+F15705AA09

Looks like I will be putting mine back together in the next few days once I run some "free" miles up on the salvage ccm. :-D

[NomakeWan]

I'm posting this for those who understand the protocol. Please don't post a public dissertation about how I accomplished it if you figure it out.

TX+F15605B4
RX+F1570500B3
TX+F15A040020002071
RX+F15604B5
TX+F15605B4
RX+F15705AA09

That is insanely cheeky, I like it.