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Home >> Chevrolet >> 1998 >> Venture Base, Van Cargo Extended >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0135 - Ho2S Heater Circuit Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Allow engine to completely cool down before proceeding. Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. If voltage changes from about 300-600 mV, see DIAGNOSTIC AIDS. If voltage does not change as indicated, go to next step.
  3. Remove and inspect fuse for HO2S 1 ignition feed circuit. If fuse is blown, go to step 15). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect HO2S 1 connector. With test light connected to ground, probe ignition feed circuit terminal at HO2S 1 harness connector. If test light does not illuminate, go to step 7). If test light illuminates, go to next step.
  5. Connect a test light between heater ground circuit and ignition feed circuit terminals at HO2S 1 harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  6. Allow HO2S 1 to cool for a minimum of 10 minutes. Using DVOM, measure resistance between ignition feed circuit and heater ground circuit terminals at HO2S 1 pigtail. If resistance is 3.4-4.4 ohms, go to step 9). If resistance is not 3.4-4.4 ohms, go to step 14).
  7. Repair open in HO2S 1 ignition feed circuit. After repairs, go to step 16).
  8. Repair open in HO2S 1 heater ground circuit. After repairs, go to step 16).
  9. Check for poor connection at HO2S 1 harness terminals. Repair as necessary. After repairs, go to step 16). If terminals are okay, go to next step.
  10. Turn ignition off. Disconnect PCM connector. Measure resistance of signal circuit and ground circuit between PCM and HO2S 1 harness connector. If both readings are less than 5 ohms, go to next step. If one or both readings are 5 ohms or greater, repair open in appropriate circuit. After repair is completed, go to step 16).
  11. Check for poor signal circuit or ground circuit terminal connection at HO2S 1 harness connector. Repair as necessary. After repairs, go to step 16). If terminals are okay, go to next step.
  12. Check for poor HO2S 1 ground circuit terminal at PCM. Repair as necessary. After repairs, go to step 16). If terminal is okay, go to next step.
  13. Check for poor HO2S 1 signal circuit terminal at PCM. Repair as necessary. After repairs, go to step 16). If terminal is okay, go to next step.
  14. Replace oxygen sensor. After replacing sensor, go to step 16).
  15. Locate and repair short to ground in HO2S 1 ignition feed circuit. Replace fuse. After repairs, go to next step.
  16. Allow engine to completely cool down before proceeding. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. If voltage changes from about 450 mV to 600 mV or from about 450 mV to 300 mV, repair is complete. If voltage does not change as indicated, repeat step 2).
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