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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 377 (Engine Controls - Self-Diagnostics - 4.3L) >> Diagnostic Tests >> DTC P0135, P0141 Or P0155: Ho2S Heater Circuit (Bank 1 & 2, Sensor 1 & 2) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Whenever the HO2S heaters are commanded ON with a scan tool, they will continue to be pulsed ON once per second until the ignition is turned OFF for 30 seconds.
  2. Turn ignition on, with engine off. Command the HO2S heaters ON with a scan tool. Wait 15 seconds to allow the HO2S heater current to stabilize. Observe the affected HO2S heater current parameter with a scan tool. Is the HO2S heater current parameter within 0.25-2.50 amps? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  4. Inspect the OXYSEN fuse. Is the OXYSEN fuse open? If yes, go to next step. If no, go to step  6.
  5. Test the ignition 1 voltage circuit for a short to ground. Did you find and correct the condition? If yes, go to step  20. If no, go to step  8.
  6. Disconnect the affected HO2S. Turn ignition on, with engine off. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test light that is connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  17.
    7. NOTE: The test light may blink prior to commanding the heaters ON. This is because the heaters were commanded ON in a previous step. To command the heaters OFF, turn ignition off for 30 seconds.
  7. Connect a test light between the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side and the HO2S heater low control circuit of the HO2S harness connector on the engine harness side. Command the HO2S heaters ON with a scan tool. Does the test light blink once per second? If yes, go to step  9. If no, go to step  10.
    8. NOTE: Perform the following test on all HO2S which are supplied voltage by the suspect circuit.
  8. Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Is any sensor shorted to ground? If yes, go to step  18. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  9. Using a DVOM, measure the resistance of the HO2S heater low control circuit and ignition 1 voltage circuit. Is the resistance of either circuit more than 3 ohms? If yes, go to step  16. If no, go to step  14.
  10. Is the test light on steady? If yes, go to next step. If no, go to step  12.
  11. Test the HO2S heater low control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  20. If no, go to step  15.
  12. Test the HO2S heater low control circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  20. If no, go to next step.
  13. Test the HO2S heater low control circuit for an open. Did you find and correct the condition? If yes, go to step  20. If no, go to step  15.
  14. Test for an intermittent and for a poor connection at the HO2S. Did you find and correct the condition? If yes, go to step  20. If no, go to step  18.
  15. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  20. If no, go to step  19.
  16. Repair circuit with high resistance. After repairs, go to step  20.
  17. Repair open in the ignition 1 voltage circuit. After repairs, go to step  20.
  18. Replace affected HO2S. See appropriate REMOVAL & INSTALLATION article. After repairs, go to next step.
  19. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  20. Replace the OXYSEN fuse, if necessary. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  21. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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