Quote Originally Posted by lionelhutz View Post
The VSS sensor signal should be capable of driving both inputs. I'm thinking you're just seeing a ground issue between the circuits. I'd try connecting only the high side of the VSS to the DRAC. That should be pin 21 on the '0411 to pin C12 on the DRAC picture Dave posted. Both should be ppl/wht wires.

If that doesn't work, then ohmmeter the VSS wires into each module and see which ones are connected to the ground terminals.

The ppm for each signal is listed on the DRAC pictures. Speedometer is 2000ppm, cruise is 4000ppm and the RWAL is 128,000ppm. So, the speedometer would read double and the RWAL would not work if you used the VSS output on the PCM. You could fix the speedometer with a frequency divider circuit, but the RWAL would be lost.


Hello Lionelhutz,

Thank you for your input, i`m not sure i have the DRAC on my truck, haven`t found it, it seems that I don`t have it.

I was thinking of changing the RWAL module to a full 4 wheel ABS module of the same 1998 Tahoe i got the wiring from, and getting the hubs, sensors, and sensor plates for the front wheels. Then i gues i will be able to use the PCM C50 speed signal to run it...

Before i have paralleled the VSS signal right out from the sensor to PCM and speedo, and unles i dropped one of either of them would work, i will try using just hi side, all thaw, i have to measure, in my 1990 schematics the Hi signal is YEL (not PPL/WHT) and on the 1998 Hi is PPL/WHT, that is where the problem could have been hiding, that is probably the reason the cluster didn`t work in parallel with PCM...

I will try connecting the wiring back to the vehicle this weekend and see if it all works out fine or not, i`d bother splice to connect the speedo at the fender, under the hood, then splicing in under the car at the trans...