TEC-II - serial protocol

[Zublin, Bryan (SD-MS)]

This email was posted to the Toyota-mods list and I received permission from 
the author to post it to the DIY_EFI list as it is relevant.

Bryan Zublin
bzublin at nlvl.com
 ----------
From: GSMnow at aol.com
To: fjo at escape.ca; toyota-mods at cyberauto.com
Subject: Re: TEC-II - serial protocol???
Date: Saturday, August 02, 1997 8:52AM

For the programs that I have written to interogeat my TEC, this is what is 
in
my notes. Wow, it has been a while since I messed with this stuff. A little
dissclaimer here, this info was arrived at by experimenting with a prom
version 33 TEC !! unit, there is no gurantee that it will work on any other
version.

open the serial port for no handshaking no parity at 2400 bps 8 bit

Send the string   T8       yes just a capital T and an 8 no return or
anything else, and there must be a short amount of time between them, fast
computers sometimes crash the link without a delay.

The TEC will respond by sending back 17 bytes of data. The first 2 bytes are
the rpm sent as a 16 bit number, first byte is the high 8 bits. But it is 
not
the exact rpm, I have to multiply the 16 bit number by 1.4652, 1.5 is close
enough

manifold pressure is the fourth byte with 0 to 255 representing the 0 to 5
volts from the MAP sensor, mine has a little offset and tops out at 208 kpa
or about 15.5 psi of boost. I use the calculation raw MAP val * .7378 +
20.6692 to get kpa from the 0 to 255 value

ignition advance is byte 3. 0 is zero advance and each count is 1/4 degree 
to
60 degrees at 240

coolant temp is the 5th byte   air temp is the 9th byte  I have not got the
scaling for these yet.

tps sensor is byte 10    0 - 255 is 0 to 5 volts

O2 sensor is on byte 16 with 0 to 255 equal to 0 to 1 volt

battery volts is on byte 11     forgot the scale

Knock sensor is byte 8       big number is knocking

Accelerator pump appears to be on byte 7

The current gama value being used by the injection appears to be byte 6

I also remember finding bits that change when it is rich or lean and trying
to correct, and when the injectors would go into coast down cut out, but I
can't find thi sinfo now

I hope this helps someone. I have several data logging and tuning aids I 
have
written, but they are giving me trouble trying to get them working on my
HP200 palmtop. I will be using the huge 1989 386sx laptop I wrote them on
today.

Gary M.