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Home >> Chevrolet >> 1998 >> Forward Control P30, 6.5 F, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 5.7L) >> Diagnostic Trouble Codes >> DTC P0135 - Ho2S Heater Circuit Bank 1, Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Install scan tool. Turn ignition on, with engine off. Monitor HO2S voltage using scan tool. If HO2S voltage gradually decreases by .15 volt (150 mV), see DIAGNOSTIC AIDS. If HO2S voltage does not gradually decrease by .15 volt (150 mV), go to next step.
  3. Check for open HO2S fuse. If fuse is open, go to step 12). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect HO2S connector. Using test light connected to ground, probe HO2S connector terminal "D" (engine harness side). If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  5. Connect test light between terminals "C" and "D" of HO2S connector (engine harness side). If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  6. Allow HO2S to cool for at least 10 minutes. Using DVOM, check resistance between HO2S ignition feed and heater ground circuit at HO2S pigtail. If resistance is 3-10 ohms, go to step 9). If resistance is not 3-10 ohms, go to step 11).
  7. Check for open HO2S ignition feed circuit. After repairs, go to step 14).
  8. Repair open in HO2S heater ground circuit. After repairs, go to step 14).
  9. Check for poor connection at HO2S. If a problem is found, go to step 14). If connection is okay, go to next step.
  10. Turn ignition off. Disconnect VCM harness connector. Check resistance between HO2S signal and low circuit terminals at VCM connector. If resistance is greater than 5 ohms, go to step 13). If resistance is not greater than 5 ohms, go to next step.
  11. Replace HO2S. After replacing sensor, go to step 14).
  12. Check for short to ground in battery feed circuit. Repair as necessary. Replace fuse. After repairs, go to step 14).
  13. Repair open or poor connection in HO2S signal or HO2S low circuit. After repairs, go to next step.
  14. Allow engine to cool down for about 30 minutes. Turn ignition on, with engine off. Using scan tool, select DTC and CLEAR DTC INFO functions. Monitor HO2S voltage. If voltage gradually decreases by 150 mV, go to next step. If measured voltage does not gradually decrease by 150 mV, repeat step 3).
  15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test. If not additional DTCs are displayed, system is okay.
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