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Home >> Saturn >> 2000 >> LS Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0140: Ho2S Circuit - Insufficient Activity - Sensor 2 >> Diagnostic Procedures

Diagnostic Procedures

  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.
  2. Operate engine at 1500 RPM for several minutes. Ensure ECT is greater than 176°F (80°C). Using scan tool, monitor HO2S2. If voltage reading is within 425-460 mV, go to next step. If voltage reading is not within 425-460 mV, problem is intermittent. See DIAGNOSTIC AIDS .
  3. Turn ignition off. Disconnect HO2S2 harness connector. Turn ignition on, with engine off. Using a jumper wire, connect jumper wire between ground and HO2S2 harness connector terminal "A" (Tan/White wire), and then between ground and terminal "B" (Purple wire). Observe scan tool reading for both terminals. If voltage reading is not less than 100 mV, go to next step. If voltage reading is less than 100 mV, check for terminal tightness. Repair as necessary. If terminals are okay, replace HO2S2 sensor.
  4. Using a DVOM, check voltage between ground and HO2S2 harness connector terminal "B" (Purple wire). If voltage reading is less than 300 mV, go to next step. If voltage reading is 300-600 mV, replace PCM. If voltage reading is greater than 600 mV, go to step  6.
  5. Check for terminal tightness or open in circuit between HO2S2 harness connector terminal "B" (Purple wire) and PCM. See WIRING DIAGRAMS article. Repair as necessary. If circuit or terminals are okay, replace PCM.
  6. Check for terminal tightness or open in circuit between HO2S2 harness connector terminal "A" (Tan/White wire) and PCM. See WIRING DIAGRAMS article. Repair as necessary. If circuit or terminals are okay, replace PCM.
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