Throttle Position Sensor: Adjustments

Linkage Measurement:

CAUTION: Before attempting to test the Throttle Position Sensor (TPS), verify the linkage adjustment dimension shown in the figure above. This dimension MUST be 126.5 mm (5.0 inches) BEFORE testing. For linkage adjustment procedures, refer to Throttle Linkage Adjustment.

CAUTION: Before testing the TPS, verify that the engine is set at correct low idle speed. Refer to Idle Speed Adjustment. This can be found in the Fuel Delivery and Air Induction system adjustments section.

1. After confirming the correct linkage adjustment and idle speed, proceed to the following:

Throttle Position Sensor Location:

2. Attach a paper clip into the center terminal of the TPS electrical connector. Do not remove the connector from the TPS for this test.
3. Attach the positive lead of a voltmeter to this paper clip and the negative lead to a good ground.
4. Turn the ignition switch to the ON position. Do not start engine.
5. The voltage at the TPS center terminal should be 1.0 volt (+/- 0.2 volt) with linkage at idle position. The voltage at the wide open throttle position should be 3.5 volts (+/- 0.4 volts). If voltage is not correct, proceed to adjusting linkage.

Throttle Lever Linkage Adjustment:

6. The linkage rod connecting the throttle lever to the fuel injection pump lever is adjustable. To prevent damage to the ends of linkage, attach locking-type pliers to the flat located on the linkage rod before loosening locknuts.
7. Loosen the right-hand-threaded nut.
8. Loosen the left-hand-threaded nut.
9. Slowly rotate the flat on the linkage rod (lengthen or shorten) to achieve 1.0 volt (+/- 0.2 volts) on the voltmeter with the linkage in the idle position. With the throttle in the wide open position, voltage should be 3.5 volts (+/- 0.4 volts). Do NOT lengthen or shorten the linkage rod more than 1 mm from the dimension shown. If voltage requirements cannot be met by linkage adjustment (125.6 to 127.6 mm), replace the TPS.
10. Tighten both nuts after adjustment.
11. With the engine OFF, operate the throttle from accelerator pedal and check for throttle lever action and binding. Be sure throttle lever stop is against the low idle speed screw after throttle is released.
12. Be sure of wide open throttle (WOT) when accelerator pedal is pressed to the floor. This is checked by observing throttle lever breakover position. Proceed to the following:
a. Key OFF and engine OFF for this test.
b. Two people are needed for this test. From inside of the vehicle, press the accelerator pedal about half-way to the floor. Movement of both the throttle lever and throttle lever-to-injection pump lever linkage rod should be observed.
c. Continue to press the accelerator pedal to the floor. If throttle lever breakover is operating correctly, the throttle lever-to-injection pump lever linkage rod should have stopped moving while the throttle lever continues to move towards the rear of vehicle.
13. Again, check and verify low idle speed. Adjust if necessary.