TA-Swede

iTrader: (4)

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.

slow

iTrader: (7)

2000 f-bodys do not have an oil pressure sensor that goes to the pcm, so you won't get the data.

TA-Swede

iTrader: (4)

I thought there was an "Oil pressure sender voltage" that could be translated into pressure ?

slow

iTrader: (7)

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

TA-Swede

iTrader: (4)

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.