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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G3500, VAN PASSENGER EXTENDED, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 4 (ENGINE CONTROLS SELF-DIAGNOSTICS - 5.0L & 5.7L)DIAGNOSTIC TESTSDTC P0121: TP SENSOR PERFORMANCEDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 F

Diagnostic Procedures

2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 FSECTION Diagnostic Procedures
WARNING: This page is about a different variant/trim than selected.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. Install scan tool. Turn ignition on, engine off. If scan tool displays throttle angle at more than 2 percent, go to step  6. If scan tool does not display throttle angle at more than 2 percent, go to next step.
    3. NOTE: Engine must remain off for this step.
  3. Depress throttle slowly to Wide Open Throttle (WOT) while watching throttle angle increase through specified range. If TP sensor range reaches a maximum of 100 percent, go to next step. If TP sensor range does not reach a maximum of 100 percent, go to step  10.
  4. Release throttle. If scan tool displays throttle angle at more than 2 percent, go to step  6. If scan tool does not display throttle angle at more than 2 percent, go to next step.
  5. DTC is intermittent. If any additional DTCs are set, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no additional DTCs are set, see DIAGNOSTIC AIDS .
  6. Disconnect TP sensor connector. See COMPONENT LOCATIONS . If scan tool displays TP sensor at zero volts, go to next step. If scan tool does not display TP sensor at zero volts, go to step  9.
  7. Turn ignition off. Using test light connected to battery voltage, probe TP sensor connector terminal "B" (Black wire). See Figure. If test light is on, go to next step. If test light is off, go to step  14.
  8. Turn ignition on, engine off. Using a DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire) and ground. If voltage is more than 5.2 volts, go to step  15. If voltage is not more than 5.2 volts, go to step  19.
  9. Turn ignition off. Disconnect PCM C2 connector. Turn ignition on, engine off. Using a DVOM, measure voltage between TP sensor connector terminal "C" (Dark Blue wire) and ground. If voltage is more than zero volts, go to step  13. If voltage is not more than zero volts, go to step  22.
  10. Turn ignition off. Disconnect TP sensor connector. Connect a jumper wire between TP sensor connector terminals "A" (Gray wire) and "C" (Dark Blue wire). See Figure. Turn ignition on, engine off. If scan tool displays throttle angle at 100 percent, go to step  17. If scan tool does not display throttle angle at 100 percent, go to next step.
  11. Turn ignition on, engine off. Using a DVOM, measure voltage between TP sensor connector terminal "A" (Gray wire) and ground. If voltage is about 5.2 volts, go to next step. If voltage is not about 5.2 volts, go to step  16.
  12. Turn ignition off. Disconnect PCM C2 connector. Using a DVOM, measure resistance of Dark Blue wire between TP sensor and PCM. If resistance is about zero ohms, go to step  22. If resistance is not about zero ohms, go to step  18.
  13. Repair short to voltage in Dark Blue wire between TP sensor and PCM. After repairs, go to step  24.
  14. Repair open in Black wire between TP sensor and PCM. After repairs, go to step  24.
  15. Repair short to voltage in Gray wire between TP sensor and PCM. After repairs, go to step  24.
  16. Repair low voltage condition in Gray wire between TP sensor and PCM. After repairs, go to step  24.
  17. Check TP sensor connector for poor connections. If problem was found, go to next step. If problem was not found, go to step  19.
  18. Repair circuit as necessary. After repairs, go to step  24.
  19. Check throttle shaft, linkage, throttle and cruise cables for binding and sticking. If problem was found, go to next step. If problem was not found, go to step  21.
  20. Repair throttle shaft, linkage, or cables as necessary. After repairs, go to step  24.
  21. Replace TP sensor. After repairs, go to step  24.
  22. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  24. If problem was not found, go to next step.
  23. Replace PCM. Program PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  24. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step  2.
  25. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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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.