I just finished swapping my Blazer engine into a Jeep and I'm trying to get a signal from the gear driven, 3 wire speed sensor from the Jeep TCase to my Blazer's ECM. All I can find is that the Blazer VSS wires are "High" and "Low". What exactly does that mean? Does anyone know if this is even possible?

 

One of the wires on your Jeep sensor is probably 12V+ and the other two are the same as the Blazer. What year/model is the Jeep? I can probably find you a wiring diagram. The other two wires would be the "high" and "low". I don't think you can do any damage by hooking them up to see if it works, then reversing them if it doesn't.

Also, the number of pulses from the Jeep VSS may be wrong for the Blazer ECM. You may need to have it reprogrammed or replace the existing Jeep VSS with one that puts out 40 pulses per revolution.

 

The Jeep is an '89 YJ, the speed sensor wires are 12v, 5v, and ground. I've grounded the ground wire and hooked the other 2 up to the Blazer wiring both ways but get no signal. If I understand correctly, the Jeep sensor needs to be powered and the Blazer sensor doesn't? So I need to run power to the sensor and hook up the other wire and the ground to the Blazer wires? Also, I have had the PCM programmed for the Jeep sensor but mainly need a signal so the engine runs right.

 

In that case, yes, you want to hook up the 12V wire on the Jeep sensor to power. The 5V should be HI and the ground should be LO. I'm not sure why it's not working if you hooked it up that way.

 

Okay, I will try it that way. I understand why it's not working the way I have it now. I don't have power to the sensor. Thank you for your help!

 

No problem. Good luck!