Many COMPUSHIFT customers are using a carbureted gasoline or diesel engine. For these applications, the throttle position sensor provided in the COMPUSHIFT kit is used. But, if you use COMPUSHIFT with an electronically fuel injected engine, you can often use the existing throttle position sensor instead of the provided one. Here’s a little explanation on how the TPS works, and how to use the existing one:

A throttle position sensor usually has three wires: +5 power, ground, and signal. The power and ground wires supply a reference voltage to either side of a variable resistor. As the shaft rotates, the signal wire has a voltage varied between +5 and ground.

In order to connect COMPUSHIFT to an existing TPS, you only need to connect two wires, the ground wire and the signal wire. These can be piggybacked on top of the existing wiring using an in line wiretap, but they should be done as close as possible to the sensor. The +5 volt wire coming from the COMPUSHIFT should be left disconnected, but insulated to prevent a short circuit.