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HOMESERVICE MANUALSCHEVROLET2001CAVALIER LS, 2.4 TREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L & 2.4LDIAGNOSTIC TESTSDTC P0134: O2S1 CIRCUIT - INSUFFICIENT ACTIVITY (2.2L - CNG)DIAGNOSTIC PROCEDURES
2001 Chevrolet Cavalier LS, 2.4 T

Diagnostic Procedures

2001 Chevrolet Cavalier LS, 2.4 TSECTION Diagnostic Procedures
  1. If alternative fuels engine controls diagnostic system check has been performed, go to next step. If alternative fuels engine controls diagnostic system check has not been performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)  under SELF-DIAGNOSTIC SYSTEM. After performing alternative fuels engine controls diagnostic system check, go to next step.
  2. Using scan tool, communicate with AF ECU. Record DTC data, clear DTCs and reset fuel trim values. Start engine and allow to idle until normal operating temperature is reached. Using scan tool, monitor suspect O2S voltage. If O2S voltage is fixed between zero and one volt, go to step  5 . If O2S voltage is not fixed between zero and one volt, go to next step.
  3. Conditions necessary to set DTC are not present at this time. Check for intermittents open or high resistance in Purple wire between O2S connector terminal "B", PCM connector C2 terminal No. 22 and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A", PCM connector C2 terminal No. 21 and AF ECU White/Clear connector C002 terminal No. 5. See Figure and Figure . Check for poor connections at PCM, AF ECU and O2S. Check for high resistance in AF ECU ground circuits. Check for an exhaust leak approximately 12" upstream from O2S. Repair as necessary. After repairs, go to step  16 . If connections, components and circuits are okay, go to next step.
  4. Fault is not present at this time. If any additional DTCs are set and need to be repaired, go to appropriate diagnostic procedure. If no additional DTCs are set, go to DIAGNOSTIC AIDS  .
  5. Start engine and allow to idle until normal operating temperature is reached. Using scan tool, communicate with AF ECU. Using scan tool, select special functions and force a switch over to gasoline. Communicate with PCM. Verify engine is operating in closed loop fuel control. Monitor suspect O2S voltage. If O2S voltage is fixed between zero and one volt, go to next step. If O2S voltage is not fixed between zero and one volt, go to step  11 .
  6. Turn ignition off. Disconnect suspect O2S connector. Connect a fused jumper between negative battery terminal and O2S connector terminal "B" (Purple wire). Turn ignition on. Monitor suspect O2S voltage. If O2S voltage is less than 20 mV, go to step  10 . If O2S voltage is more than 20 mV, go to next step.
  7. Turn ignition off. Remove fused jumper wire. Disconnect PCM connectors. PCM is located inside right front fender. Using DVOM, measure resistance of Purple wire between O2S connector terminal "B" and PCM connector C2 terminal No. 22. See Figure . Also measure resistance of Tan wire between O2S connector terminal "A" and PCM connector C2 terminal No. 21. If resistance for both circuits is less than 5 ohms, go to next step. If resistance in either circuit is more than 5 ohms, go to step  9 .
  8. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  16 . If connections are okay, go to step  15 .
  9. Repair open or high resistance in circuit that measured more than 5 ohms. After repairs, go to step  16 .
  10. Check for exhaust leaks approximately 12" upstream of O2S. Repair as necessary. After repairs, go to step  16 . If exhaust is okay, go to step  13 .
  11. Turn engine off. Disconnect O2S, PCM and AF ECU connectors. PCM is located inside right front fender. AF ECU is located behind left front fascia, below headlight. Using DVOM, check for continuity in Purple wire between O2S connector terminal "B" and AF ECU White/Clear connector C002 terminal No. 4 and Tan wire between O2S connector terminal "A" and AF ECU White/Clear connector C002 terminal No. 5. See Figure . Repair as necessary. After repairs, go to step  16 . If circuits are okay, go to next step.
  12. Replace AF ECU. See ALTERNATE FUEL ENGINE CONTROL UNIT under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECU with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL UNIT  under PROGRAMMING. After performing repairs and procedures, go to step  16 .
  13. Perform fuel system diagnosis then return to this test step. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (2.2L - CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system problem is found and repaired, go to step  15 . If fuel system problem is not found and repaired, go to next step.
  14. Replace O2S. After repairs, go to step  16 .
  15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. To perform CKP variation learn procedure, a switch-over to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switch-over. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing repairs and procedures, go to next step.
  16. Reconnect all disconnected components and connectors. Using scan tool, clear DTCs for PCM and AF ECU. Start engine and allow to idle until engine reaches normal operating temperature. Select DTC and specific DTC function. Enter DTC number and operate vehicle, within conditions for setting this DTC, until scan tool indicates diagnostic has run. If DTC diagnostic runs and passes, system is okay. If DTC resets, go to step  2 .
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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.