Throttle Position Sensor: Adjustments

Before performing any adjustments, repair any vacuum leaks, ensure all switch tests pass, check that ignition timing is correct and turn A/C off. Depress Outside Temp button to turn off Outside Temperature indicator.
1. Turn ignition on, then enter diagnostics. Note all trouble codes displayed between the time ``-1.8.8'' is displayed and ``.7.0'' is displayed. Diagnose any trouble codes by referring to appropriate diagnostic procedure before continuing to step 2.
2. Perform ``switch tests'' as previously described. Diagnose any trouble codes which do not pass by referring to appropriate diagnostic procedure.
3. Remove air cleaner, then run engine until normal operating temperature is reached. Check engine timing with A/C off and adjust as necessary. Refer to ``Fixed Mode Spark Procedure'' under ``Diagnosis.''
4. Turn off all electrical accessories, shift transmission to Park and center the steering wheel, then retract ISC motor plunger as follows:
a. Unlock ISC motor electrical connector. Do not disconnect connector from motor.
b. Open throttle and hold at approximately 1500 RPM, while simultaneously closing the throttle switch by depressing ISC plunger.
c. With ISC plunger fully retracted, disconnect ISC motor electrical connector while holding throttle open and throttle switch closed. Do not power ISC motor for more than 4 seconds while fully retracted to avoid damage to ECM.
d. Release throttle switch and return throttle to idle.
e. Ensure ISC plunger is not contacting throttle lever. Adjust as necessary by turning in plunger with pliers until there is no longer contact.
5. Enter diagnostics, then turn ``A/C Clutch'' status light off by depressing ``outside temp'' button.
6. Display parameter .1.1 and observe ``engine speed'' at minimum air. If displayed value is 40-50, proceed to step 7. If ``engine speed'' display does not read between 40 and 50, connect tachometer to engine and adjust throttle stop screw to obtain 450 RPM. If engine speed cannot be adjusted to 450 RPM, ensure throttle is not held off minimum stop screw due to binding linkage or interference with ISC motor plunger.
7. Turn ignition on, enter diagnostics and display parameter .0.1.

Fig. 38 TPS voltage specification chart:

Fig. 39 Throttle position sensor adjustment:

8. Open throttle, then let it snap fully shut against throttle stop screw. If value of parameter .0.1 is 0, proceed to step 12. If value of parameter is not 0, disconnect TPS electrical connector and measure voltage between terminals B and C of ECM side of TPS connector. Refer to Fig. 38 for specifications.
9. Reconnect TPS, then connect suitable digital voltmeter to TPS harness test point, Fig. 39, as follows:
a. Turn ignition on. Do not start engine.
b. Connect positive lead of voltmeter to test point corresponding to pin A (dark blue wire).
c. Connect negative lead of voltmeter to test point corresponding to pin B (black/white wire).
d. Set voltmeter to the 2 volt DC scale.
10. If TPS voltage is within .05 volts of values shown in Fig. 38, with throttle fully shut against throttle stop screw, proceed to step 12.
11. If voltage reading is not within specifications, loosen TPS attaching screws just enough to allow rotation of the sensor. With throttle fully shut against throttle stop screw, turn sensor until voltage is within specifications, then retighten attaching screws. To avoid damaging the sensor, do not overtighten TPS attaching screws. After tightening screws, recheck voltmeter reading to ensure voltage is still within specifications.
12. With throttle fully shut against throttle stop screw and ISC motor fully retracted, adjust gap between ISC motor plunger and throttle lever to .060 inch by turning plunger adjusting screw as necessary.
13. Disconnect test equipment and reconnect all connections.
14. Turn ignition off for at least 10 seconds, then start engine and check ISC motor for proper operation. If any of the adjustments performed set an intermittent trouble code, the code can be eliminated by entering diagnostics, clearing the stored code(s) and turning ignition off for a minimum of 10 seconds.