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TPS - 1987-1990

The 1987-90 sensor has two pigtail leads. One has an in-line 3 pin
connector, containing 3 wires. The other has a square four pin
connector with 3 wires. The square connector is the one that is used
for the transmission controller. These wires can be identified by the
letters which are stamped into the connector.

Adjustment is simple though backward by most TP standards. With the
harness connected, test the voltage on pins A, B & D. The voltage on
pin A (reference voltage) should be approx. 5v

Voltage on pin D (ground) should be less than 0.1v. If the voltage is
higher, an additional ground wire can be spliced into the circuit.

Pin B is the TPS signal to the controller. The voltage on pin B should
be 4.0 - 4.4v at closed throttle. At full throttle, the voltage should
be 0.2-0.5v. The TP sensor has elongated holes for the hold-down screws which allow it to be ajusted.

Adjustment is as follows: (comments in brackets are mine)

1. Turn the ignition switch to the "ON" position

2. There are 2 wire harness connectors attached to the TPS. Inout/output voltage is checked at the SQUARE, FOUR TERMINAL CONNECTOR (though it only actually has 3 pins). The terminals are identified by the letters A,B,C,D molded into the connector.

3. Do not unplug the connector. The voltmeter leads must be inserted through the back of the connector to make contact with the terminals. Connect the positive lead to terminal A and the negative lead to terminal D.

4. With the throttle plate in the closed position, note the "input" voltage. It should be approx 5.0 volts

5) Remove the voltmeter positive lead from terminal A and connect it to terminal B. The "output" voltage should be 4.2 volts - 82% of input voltage. (NOTE: on my XJ, the input voltage was only 4.6 volts so I had to adjust the closed throttle output voltage to 3.8 volts as this is 82% of 4.6)
If this is not the case, continue with this procedure

6. Adjust output voltage as follows: with the voltmeter leads still attached to, carefully loosen the sensor mounting screws and slowly rotate the sensor until the output reading is 4.2 volts with the throttle closed (or 82% of your input voltage). Then, toghten the sensor mounting screws securely.