The throttle position sensor is used by the TCU to determine what the driver’s intent is. The TCU will use the TPS, engine RPM and road speed to calculate a shift pattern to use. This sensor is very important and must be a stable signal. Most of the time the TCU will operate side by side to the ECU. The TCU can tap into the signal from the existing TPS or as with Spitronics ECU’s there is a yellow wire that is installed in the harness for this signal. Do not connect any supply or earth to existing TPS connections. Just the signal wire is connected. See the drawings on this.

TPS Sensor Wiring MTSX02-2 Stand Alone

TPS Sensor Wiring MTWX02-2 With ECU

Operation:
The TPS is a variable resistor normally around 5K ohms. The signal voltage varies as the wiper moves. It is connected to 5 volts from the ECU and then the wiper signal will produce a voltage between 0 and 5 volts, proportional to the angle of the throttle plate.

Which Pin is which?
Use a multi-meter set to the 20,000 ohm (20 K) range.

– With throttle closed, find the two pins with the lowest resistance between them. They are C & B. The remaining pin is the 5 V pin A.

– With one probe on the 5 V pin A, find the pin whose resistance changes when the throttle moves. This is the Signal pin B.

– The remaining pin is the earth pin C.

This same route can be used on a four pin throttle position sensor, note that only three of the four pins will be connected or one pin may be a switch to ground or 5 Volt as an idle activation switch. The Spitronics ECU does not require this pin.

Pre-load the Sensor
The sensor has a dead band at either end so it must be rotated slightly to move the wiper into the operating range of the sensor.

Connecting the TCU TPS to an existing ECU TPS sensor.

TPS Sample Pin outs: