16197427 PCM info

[WEG1192 at aol.com]

I have found out some interesting info for those using a 16197427 PCM (194-95 
TBI PCM). According to Jagsthatrun, you need a 40 reluctor ring type speed 
sensor in the tranny for this PCM to get a speed signal. But on a hunch, I 
ran one with a JTR 4 pulse per rev magnetic speed sensor and got a reading 
double my actual speed. Also, I got no reading at all until about 45 MPH and 
up, and an erratic one at that. So, knowing that the 2000 PPM speed sensor 
was an optical one and not a magnetic and that it would give me half the 
pulses, I tried the 2000 PPM on the 16197427 and it works perfectly. 
Apparently the 40 tooth speed sensor goes to a DRAC which then sends a 2000 
PPM signal to the PCM. This means you don't need  the DRAC at all and can run 
a cable driven speed sensor directly into the later model  PCM.

Now, why would you want to do that you ask? So that you can use Datamaster 
with a P4 PCM and get some high speed data for tuning a TBI system. Problem 
is, even with a working speed sensor, I can't get the BLM (LT Counts) to move 
off 128. The Integrator  (ST counts) moves as it should and is correcting the 
AFR in closed loop, but my BLMs stay locked at 128 for a full 20 minute 
drive. The fuel trim cell #s shift around as well. Anyone know what could be 
keeping the BLM locked at 128?

Thanks,
JW
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