Hi guys,

I've been trying to get my cruise control working in my conversion car (94 Lt1/T56 inside an 84 XJ6). However, I'm still having wierd issues with my speed readouts, and what speed the PCM says the car is going. For the LT1 cruise control to engage, I have to be going around 40mph. However, when I'm on the freeway, my speed on datamaster clocks in at 15mph.

My speedometer is reading correctly at the moment because I am using an external damper box. Does anyone have an idea what could be causing this?

I've attached a link to my datamaster file. Can anyone help me out?

http://dl.dropbox.com/u/24984984/Freeway.uni

Here's my tunercats file too, if that helps...

http://dl.dropbox.com/u/24984984/94C...ler%20Mods.bin

 

Was the PCM flashed for an M6 trans? The automatic VSS outputs 40 pulses per output shft rev. The M6 outputs 17 pulses per rev. That means if you are still running the A4 program in the PCM, the PCM will only report (17/40) x the actual MPH. At a true 40MPH, the PCM would indicate 17 MPH. Sounds pretty close to what you have.

Appears you have only altered the pulse signal to the speedometer, and not to the PCM.

 

The PCM was flashed correctly -- i verified it with tunercats, and posted the tune. If you open the tune in TunerCats you can see that it is set for an M6 tune. I am not throwing any A4 related codes.

If somehow TunerCats isn't flashing the PCM correctly, the speed readings still make no sense -- as you can see in the DataMaster file, the speed reaches around 14-15mph and just stays there, even though I am going around 80mph. It will read 14-15mph going a true 14-15mph as well -- it just stops at 15~. I have no idea what it means.

 

Where is the "damper" (do you mean something like the Dakota Digital SG5 box?) located in the wiring? Between the VSS and the speedo, between the VSS and the PCM, or between the PCM and the speedo? Is this primarily to compensate for the difference between the F-Body and the Jaguar speedo?

 

The damper box is very similar to the Dakota Digital box -- it is located between the PCM's speedometer output wire and the speedometer in the cab. It's use is wholly to convert the GM signal to something the Jaguar's speedometer can use. I believe the GM's signal is 4000ppm, and the Jaguar's is 2000ppm.

 

Just an update to this.. it was resolved in another forum and the problem was a corrupted PCM code load.. OP loaded a stock '95 M6 code .bin file and the PCM started displaying the correct MPH data.