GM Can info & knowledge share

[antus]

GM are actually one of the best for information sharing. Except by share, they mean sell. But it probably does cost them a lot to pay many technical writers good salaries to work with the developers to gather and create such high quality documentation.

[series8217]

Hey all, first time poster, long time lurker. I am working on a project shown here:

https://ls1tech.com/forums/automatic-tr ... oller.html

I am working on a 07 Escalade with L92 and e38 ecm. I am trying to decode $199 (TCM -> Engine Torque Request) and $19d (TCM -> Engine Speed Request). I want these for torque cut and engine blips for shifting. I don't see a $189 message ever (limited driving conditions though). Seems series8217 has good info on the $199. It is interesting that the gmw8762 has about every other can message I see on the bus but these. GM worried about liability exposing these? What gives? Anyway, I no longer have a vehicle with a 6L80 (now have 10L80) to hack. I was hoping someone might shed some light on the $19D. Thanks.

Have you logged $19D yet?

I haven't figured it all out from my LFX Impala. The input shaft RPM and gear ratio look reasonable. I don't know what the first signal is. Rolling count is a counter for every frame. The next signal is a signal protection value, which is basically a checksum. The format for this is defined in the GM docs. I suspect that's what it is because it matches the pattern.

Code: Select all

BO_ 413 TransmissionInputSpeed: 8 TCM
 SG_ NEW_SIGNAL_1 : 5|14@0+ (1,0) [0|16383] "" XXX
 SG_ RollingCount : 7|2@0+ (1,0) [0|3] "" XXX
 SG_ UnknownSignalProtection : 21|14@0+ (1,0) [0|65535] "" XXX
 SG_ InputShaftRPM : 46|15@0+ (0.25,0) [0|65535] "" XXX
 SG_ GearRatio : 56|8@1+ (0.03125,0) [0|255] "" XXX

[series8217]

Most probably, the first signal is the requested RPM and the signal protection is for that RPM field. 0 probably means no request.

[Tre-Cool]

Heres some can data logged from a car with a tcm2650 standalone controller & 6l80e.

Theres quite a few can id's with fixed data that never changes, these are likely to keep error codes from being flagged by the trans for various os/calibrations for missing modules like EBCM,BCM etc.

it can emulate the bcm for tapshift controls too along with sports mode etc.

i did this logging for Link ecu because I was getting a neutral gear when shifting from 3rd. i.e no 4,5,6 gears, i started turning off the recieve side in a trans & had the below results.

Tested removing the listening of the following in the trans, once i turned it off, and it kept working i left it off:
4F1 - shifted fine
4E9 - shifted fine
3E9 - shifted fine
2F9 - shifted fine
1F1 - shifted fine
1F3 - shifted fine
3D1 - shifted fine
1E9 - shifted fine
1A1 - BINGO, WINNER WINNER CHICKEN DINNER. shifted 1,2,3, then when it went for 4th big old neutral gear. tapshift went straight to neutral. doesnt even flag dtc codes. re-enabled to continue below.
0C1 - shifted fine
0C5 - shifted fine
0F1 - shifted fine
18E - shifted, but firmness was a bit hard.

[nmstec]

Have you logged $19D yet?

19d.png (50.83 KiB) Viewed 1065 times

1A1 - BINGO, WINNER WINNER CHICKEN DINNER. shifted 1,2,3, then when it went for 4th big old neutral gear. tapshift went straight to neutral. doesnt even flag dtc codes. re-enabled to continue below.

18E - shifted, but firmness was a bit hard.

1a1.png (48.56 KiB) Viewed 1063 times

18e.png (29.93 KiB) Viewed 1063 times

[Tre-Cool]

I've got the global-a can dbc. the log files will have the tx & rx comms between tcm-2650 & the TCM itself.

I'm going through the data from the link-tcm log now to see what could be wrong.