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Home >> GMC >> 1999 >> Forward Control 6.5 F, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0135-P0204 >> DTC P0140 >> DTC P0140: Ho2S Circuit-Insufficient Activity-Sensor 2 (1.9L SATURN) >> Diagnostic Procedures

Diagnostic Procedures

  1. If DTC P0140 and P0141 are both set, diagnose DTCs first using DTC P0141 test. Operate engine for 3 minutes or greater. Connect scan tool. Ensure ECT is at greater than 140°F (60°C). Increase engine speed to 3000 RPM. Monitor HO2S 2 voltage. HO2S 2 voltage should vary greater than and less than 450 mV. If voltage is varies as specified, problem is intermittent. See DIAGNOSTIC AIDS . If voltage does not vary as specified, go to next step.
  2. Turn engine off. Turn ignition on. Disconnect HO2S 2 harness connector. Using a jumper wire, jumper HO2S 2 harness connector terminals "A" and "B" together. If scan tool reads less than 100 mV, check tightness of harness connector terminals. If scan tool reads 100 mV or greater, go to next step.
  3. Remove jumper wire. Connect jumper wire between HO2S 2 harness connector terminal "B" and chassis ground. If scan tool reads less than 100 mV, check for open in ground circuit between sensor and chassis ground. If scan tool does not read less than 100 mV, go to next step.
  4. Remove jumper wire. Measure voltage on HO2S 2 signal circuit at harness connector terminal "B". If voltage is 300-600 mV, replace PCM. If voltage is greater than 600 mV, check for open ground circuit, terminal tightness or faulty PCM. If voltage is less than 300 mV, check for open signal circuit, terminal tightness or faulty PCM.
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