ALDL data stream information - An update

[Scot Sealander]

Ludis Langens wrote:

> The table called "TBI(ALL), and Pontiac MFI(TPI)" looks like it is the
> conversion table for the MAT sensor.  It _exactly_ matches what someone
> "reversed" out of Diacom for the MAT sensor on the Pontiac 2.8 M(P)FI.

There is a reason for that.  Most ECMs use two different pull-ups for the 
engine temp sensor.  The resulting A/D values for the temp sensor are 
then linearized, and sent out the ALDL.  The TBI's (like the 1227747) just 
use a 1k pull-up resistor for engine temp.  Because most ECMs also just use 
a 1k pull-up for MAT, the raw A/D MAT values are the same as the TBI engine 
temp values.

In both the 1k pull-up cases, the raw A/D value is sent out, rather than 
the linearized value that is often sent for engine temp.  The conversion is 
the same, as the same sensor is used in most MAT and engine coolant temp 
applications.

Scot Sealander    Sealand at clarityconnect.com