The throttle position sensor on a 1994 Honda Accord LX has two primary functions: to signal the amount of throttle opening and the speed at which it is opening. This information, along with various other sensor information, is used by the computer to make adjustments to the ignition timing and the fuel injector timing. The sensor is essentially a variable resister (potentiometer) with an operating range between 0.2 and 5 volts. The throttle position sensor is mounted on the throttle body, on the same shaft but on the opposite side of the throttle linkage. It has a round, three-wire plug.
Examine the electrical plug on the throttle position sensor. You will see three wires in a horizontal line. Reading from left to right, the first wire -- green with blue stripe -- is the computer ground, the second wire -- red with a black stripe -- is the throttle position sensor signal and the last wire to the right -- yellow with a blue stripe -- is the computer-supplied 5-volt input wire.
Connect the voltmeter black lead to a good ground on the intake manifold. Use the red lead as a probe. It has a sharp point on the tip to pierce the insulation on a wire so the probe makes contact with the wire beneath. Pierce the middle sensor signal wire with the red voltmeter probe.
Turn the ignition key on without starting the engine. The voltmeter will display between 0.3 to 0.5 volts if the sensor is good.
Open the throttle plate slowly with the throttle linkage. The voltage will be around 0.5 volts and rise to 4.7 volts at full open throttle. During the throttle movement, watch for any voltage drop-outs. This is a term for a sudden drop or lack of voltage at one point in the throttle position sensor swing. Many times, the throttle position sensor will wear out in the area of cruise since that is the most heavily used. The voltage will be going up steadily, then suddenly drop to zero and come back as soon as the sensor moves away from this spot. Failing to meet any of the above criteria justifies replacement.
Move the red voltmeter lead to the far-right and probe the yellow with a blue stripe wire. If the displayed voltage is less than 5 volts, the computer is bad. If the voltage is good, the sensor is bad.
