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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P1133: Ho2S Insufficient Switching (Bank 1; Sensor 1) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, clear DTCs. Reset fuel trim values. Start and warm engine to normal operating temperature. Using scan tool, monitor O2S voltage for sensor that applies to this DTC. Does the O2S voltage read fixed within 300-600 millivolts? If yes, go to step  4. If no, go to next step.
  3. Were any other DTCs set? If yes, diagnose affected DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, see DIAGNOSTIC AIDS .
  4. Check exhaust system for leaks upstream of suspect O2S. Leak may be very small and typically be within 12 inches of suspect O2S. Did you find and correct the condition? If yes, go to step  14. If no, go to next step.
  5. Turn ignition off. Disconnect the O2S connector for the sensor that applies to this DTC. Jumper the O2S high signal circuit to a known-good ground. Turn ignition on, with engine off. With the scan tool, monitor the O2S voltage for the sensor that applies to this DTC. Does the voltage read less than 20 millivolts? If yes, go to step  7. If no, go to next step.
  6. Turn OFF ignition. Remove jumper from O2S terminal. Disconnect PCM connector containing the O2S high circuit. Use a DMM in order to measure continuity of HO2S high signal circuit between PCM connector and O2S connector. Does resistance read less than 5 ohms? If yes, go to next step. If no, go to step  10.
  7. Check for a poor connection at PCM harness connector. Repair as necessary. After repairs, go to step  14. If connections are okay, go to next step.
  8. Disconnect PCM connector containing the O2S low signal circuit. Connect a test light between the O2S low signal circuit at the PCM and battery positive. Does the test light illuminate? If yes, go to step  12. If no, go to next step.
  9. Turn ignition off. Reconnect the O2S connector. Disconnect the PCM connector containing the PCM ground circuits if not already removed. With a DMM, measure the resistance between the O2S low signal circuit at the PCM connector and engine ground. Does the resistance measure less than 5 ohms? If yes, go to step  13. If no, go to step  11.
  10. Repair circuit with high resistance. After repairs, go to step  14.
  11. Repair high resistance in Tan wire. After repairs, go to step  14.
  12. Replace O2S sensor. After replacing sensor, go to step  14.
  13. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  15. Using scan tool, observe the stored information, Capture Info. Does 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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