Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1998TRACKER 4D UTILITY, RWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODESDIAGNOSTIC TROUBLE CODESDTC P0121: THROTTLE POSITION (TP) SENSOR SYSTEM PERFORMANCEDIAGNOSTIC TEST
1998 Chevrolet Tracker 4D Utility, RWD
Diagnostic Test
1998 Chevrolet Tracker 4D Utility, RWDSECTION Diagnostic Test
- If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK .
- Turn ignition switch to RUN position. Use scan tool to clear information function. Operate vehicle within freeze frame conditions. If DTC P0121 is displayed, go to next step. If DTC P0121 is not displayed, check the follow and repair as necessary:
- Connection at PCM and TP sensor.
- Damaged wiring harness.
- TP sensor. See SENSOR RANGE CHARTS article.
- Start engine. Allow engine to reach normal operating temperature. Turn ignition switch to LOCK position. Disconnect TP sensor harness connector. Measure resistance between terminals No. 1 (Gray/Yellow wire) and No. 4 (Gray/Red wire) at TP sensor. See Fig 1 . If resistance is 3500-6500 ohms, go to next step. If resistance is not 3500-6500 ohms, go to step 8).
- Ensure throttle plate is closed. Measure resistance between terminals No. 1 (Gray/Yellow wire) and No. 3 (Gray wire) at TP sensor. If resistance is .3-2000 ohms, go to next step. If resistance is not .3-2000 ohms, go to step 8).
- Open throttle to wide open. Measure resistance between terminals No. 1 (Gray/Yellow wire) and No. 3 (Gray wire) at TP sensor. If resistance is 2000-6500 ohms, go to next step. If resistance is not 2000-6500 ohms, go to step 8).
- Insert a .020" (0.5 mm) feeler gauge between throttle lever and throttle stop screw. Measure resistance between terminals No. 1 (Gray/Yellow wire) and No. 2 (Blue/White wire) at TP sensor. If resistance is 0-500 ohms, go to next step. If resistance is not 0-500 ohms, go to step 8).
- Insert a .031" (0.8 mm) feeler gauge between throttle lever and throttle lever stop screw. Measure resistance between terminals No. 1 (Gray/Yellow wire) and No. 2 (Blue/White wire) at TP sensor. If resistance is not infinite, go to next step. If resistance is infinite, go to step 9).
- Adjust or replace TP sensor as necessary and go to step 10).
- Replace PCM and go to next step.
- Test drive vehicle under conditions that set the DTC. Check for other DTCs. If DTCs were retrieved, perform appropriate DTC test. If no DTCs were retrieved, system is okay at this time.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.