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Home >> Pontiac >> 2000 >> Firebird Base, 2D Convertible, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Engine Control System Self-Diagnostics - 5.7L) >> Diagnostic Tests >> DTC P0140: Ho2S Circuit Insufficient Activity - Bank 1, Sensor 2 >> Diagnostic Procedures
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Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
    NOTE: Ensure HO2S is not loose. A loose sensor can cause DTC to set.
  2. Start and warm engine to normal operating temperature. Increase engine speed to about 1200 RPM for 2 minutes. Using scan tool, select ENGINE 1 DATA LIST and monitor HO2S voltage. If voltage reading is 350-550 mV, go to next step. If voltage reading is 350-550 mV, go to step  4.
  3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function, and then enter this DTC. If scan tool indicates that this test failed this ignition, go to next step. If scan tool does not indicate that this test failed this ignition, see DIAGNOSTIC AIDS .
  4. Turn ignition on, with engine off. Disconnect HO2S connector. Connect jumper wires between HO2S high and low signal circuits to battery ground. Monitor HO2S voltage with scan tool. If voltage reading is less than 200 mV, go to step  8. If voltage reading is not less 200 mV, go to next step.
  5. Remove jumper wire from HO2S low circuit. Check voltage between battery ground and HO2S low signal circuit. If voltage reading is about 5 volts, go to next step. If voltage reading is not about 5 volts, go to step  7.
  6. Turn ignition off. Disconnect PCM harness connector. Check continuity of HO2S high circuit. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  10.
  7. Turn ignition off. Disconnect PCM harness connector. Check continuity of HO2S low circuit. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  10.
  8. Check for poor connection at HO2S. Repair as necessary. After repairs, go to step  12. If connection is okay, go to next step.
  9. Replace HO2S. After replacing sensor, go to step  12.
  10. Check for poor connection at PCM. Repair as necessary. After repairs, go to step  12. If connection is okay, go to next step.
  11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  12. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2
  13. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no undiagnosed DTCs are displayed, system is okay.
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