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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 4 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.3L)DIAGNOSTIC TESTSDTC P0121: TP SENSOR PERFORMANCEDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8

Diagnostic Procedures

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION 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. NOTE: If any other DTCs are set, diagnose those DTCs first.
  2. Turn ignition on, engine off. Using scan tool, observe TP sensor angle parameter while slowly opening throttle to WOT. If TP angle increases steadily and evenly from 0-98 percent, go to next step. If TP angle does not increase steadily and evenly between 0-98 percent, go to step  4.
  3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC failed this ignition cycle, go to next step. If DTC did not fail this ignition cycle, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect TP sensor connector. See COMPONENT LOCATIONS . Turn ignition on, engine off. Using scan tool, observe TP sensor voltage parameter. If voltage is zero, go to next step. If voltage is not zero, go to step  6.
  5. Turn ignition off. Connect a fused jumper between TP sensor connector terminals "A" (Gray wire) and "C" (Dark Blue wire). See Figure. Turn ignition on, engine off. Using scan tool, observe TP sensor voltage parameter. If voltage is 5 volts, go to step  9. If voltage is not 5 volts, go to step  7.
  6. Check Dark Blue wire between TP sensor and PCM for short to voltage. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  12.
  7. Check Gray wire between TP sensor and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to next step.
  8. Check Dark Blue wire between TP sensor and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  11.
  9. Check Black wire between TP sensor and PCM for open or high resistance. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to next step.
  10. Check TP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  12.
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  13.
  12. Replace TP sensor. After repairs, go to step  14.
  13. Replace PCM. Program PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. 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.
  15. 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.