Corvette CCM Reverse Engineering Anyone?

**NomakeWan** · 10-01-2022

Originally Posted by -=Jeff=-

any one have a 94 or 95 BIN they can repost for me to look at? thanks

See attached.

As for the PASSkey thing, if you don't know it, all that should happen is your BINs will be missing the PASSkey information. The rest of the data should be intact.

**-=Jeff=-** · 10-01-2022

Originally Posted by NomakeWan

See attached.

As for the PASSkey thing, if you don't know it, all that should happen is your BINs will be missing the PASSkey information. The rest of the data should be intact.

But isn't the PASSkey Stored?

anyway, here is what I think is correct for the 1990 CCM for the flags, just based on relative locations between the 2.

**steveo** · 10-01-2022

the flash tool for these things never got well tested beyond my bench
definitely interested to see if it works for you

**-=Jeff=-** · 10-01-2022

Originally Posted by steveo

the flash tool for these things never got well tested beyond my bench
definitely interested to see if it works for you

What wires did you have connected, meaning do I need to apply power to all the power pins?

**NomakeWan** · 10-01-2022

Originally Posted by -=Jeff=-

What wires did you have connected, meaning do I need to apply power to all the power pins?

You don't need to apply power to all of the pins as many of them are tied together internally. Please follow the pinout I posted a few posts ago.

Originally Posted by -=Jeff=-

But isn't the PASSkey Stored?

It is. But if the correct key is not "inserted" (that is, the correct resistance value is not applied between pins E12 and F5) then the CCM will not allow external devices to read those locations in memory. They will appear as blank data instead of the correct PASSkey data.

**-=Jeff=-** · 10-01-2022

at this point, it is probably easier to work through my harness to get he wires I want as all the connectors are there..

**-=Jeff=-** · 10-02-2022

I am getting data on the serial bus but having this issue:

Reconnecting to ALDL bus, please wait....
ERROR! The bus is still noisy (retry)...
ERROR! The bus is still noisy (retry)...
ERROR! The bus is still noisy (retry)...
ERROR! Could not become the ALDL bus master.
ERROR! Error reading segment 0[40]
ERROR! Could not complete read procedure.

how do I get it not noisy?

**NomakeWan** · 10-02-2022

According to the source code for flashhack, those error messages in that order will be sent if no bus master is found within 5 seconds, and yet there is still data on the line every half-second for three retries.

What is likely happening here is that you did not power up the CCM in the proper sequence, and so it is not sending the proper bus master heartbeat message (which starts with F0, and is the "CCM requesting the presence of external bus master" call).

On my wiring layout I posted earlier, you'll notice two of the entries say "when key is inserted into cylinder" and "when key is turned to run position." These mean exactly as I wrote. You do not connect them until the rest are connected. Then you first "insert the key" by connecting C11 to ground, followed by "turning the key" by connecting both E4 and E5 to +12V. Doing this should tell the CCM that it should run the power on sequence, which will start broadcasting F0 diagnostic messages. It's this message which Flashhack looks for in order to become the bus master.

If you just power the CCM up but don't follow the correct sequence, it will broadcast its normal status request messages ($40 and $10) but will not broadcast the bus master request message (F0).