GM Mode22 PIDs
GM Mode22 PIDs Hi guys,
I'm writing a piece of software that reads data from the ECM and presents them in a way that could be considered a virtual dash. I've got most of it working, but I'm missing a few small pieces of information. Hopefully you guys can fill in the gaps.
First is regarding the $1991 PID (TCC Slip speed). I'm getting two data-bytes in return, but I'm unclear on how to decode them.
Right now, I'm using ((A * 256) + B)/4, but as TCC Slip can be a negative, this is not correct. (I'm also getting slip-speed of ~1300rpm at a 500rpm idle, which is also incorrect)
Should I regard the first databyte as a signed integer, and thereby get a negative value ? What factor should I divide by?
Second is the engine oil pressure, which I'm completely missing a PID for.
All this is for a 2000 F-Body.
I'm writing a piece of software that reads data from the ECM and presents them in a way that could be considered a virtual dash. I've got most of it working, but I'm missing a few small pieces of information. Hopefully you guys can fill in the gaps.
First is regarding the $1991 PID (TCC Slip speed). I'm getting two data-bytes in return, but I'm unclear on how to decode them.
Right now, I'm using ((A * 256) + B)/4, but as TCC Slip can be a negative, this is not correct. (I'm also getting slip-speed of ~1300rpm at a 500rpm idle, which is also incorrect)
Should I regard the first databyte as a signed integer, and thereby get a negative value ? What factor should I divide by?
Second is the engine oil pressure, which I'm completely missing a PID for.
All this is for a 2000 F-Body.
The pcm may support it, the corvette has an oil pressure sensor going to the pcm, the f-cars just do not use this as a pcm input.
What hex data are you getting back when it should be 500 rpms?
Ryan
What hex data are you getting back when it should be 500 rpms?
Ryan
Can't really recall. But I think I've got the TCC slip figured out.
(((signed)A * 256)+(signed)B)/8 seems to give results that are much more reasonable.
Idle slip speed is now at ~560rpm, and the formula gives me +/- 4096rpm as the slip speed, which seems like a reasonable range for GM to pick.
(((signed)A * 256)+(signed)B)/8 seems to give results that are much more reasonable.
Idle slip speed is now at ~560rpm, and the formula gives me +/- 4096rpm as the slip speed, which seems like a reasonable range for GM to pick.
