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Home >> Pontiac >> 1996 >> Firebird Formula, 2D Convertible, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - 5.7L >> Diagnostic Trouble Codes >> DTC P0140 - Ho2S Insufficient Activity Bank 1, Sensor 2 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Start and warm engine to normal operating temperature. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, select ENGINE 1 DATA LIST and monitor bank 1 HO2S 1 voltage. If voltage is varying outside of 352-552 mV range, go to next step. If not, 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 the conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function, then enter DTC P0140. If scan tool indicates that this test failed this ignition, go to next step. If scan tool did not indicate that this test failed this ignition, see DIAGNOSTIC AIDS.
  4. Turn ignition on, with engine off. Disconnect Bank 1 HO2S 1 harness connector. Jumper high and low signal circuits to ground, on PCM harness side. If voltage is less than 200 mV, go to step 8). If voltage is greater than 200 mV, go to next step.
  5. Remove jumper wire. Using DVOM, check voltage between HO2S sensor high signal circuit and ground circuit. If voltage is greater than 375 mV, go to next step. If voltage is less than 375 mV, go to step 7).
  6. Turn ignition off. Disconnect PCM harness connector. Check resistance of Bank 1 HO2S 1 low circuit. If resistance is greater than 2 ohms, repair open or poor connection as necessary. After repairs, go to step 13). If circuit is okay, go to step 9).
  7. Turn ignition off. Disconnect PCM harness connector. Check resistance of Bank 1 HO2S 1 signal circuit. Resistance should be 2ohms. If resistance is greater than 2 ohms, repair open or poor connection as necessary. After repairs, go to step 13). If circuit is okay, go to step 10).
  8. Check for poor Bank 1 HO2S 1 signal or low circuit terminal connection at HO2S harness connector. Repair or replace terminals as necessary. After repairs, go to step 13). If terminals are okay, go to step 11).
  9. Check for poor Bank 1 HO2S 1 low circuit terminal connection at PCM and replace terminals if necessary. After repairs or replacing terminals, go to step 13). If terminals are okay, go to step 12).
  10. Check for poor Bank 1 HO2S 1 signal circuit terminal connection at PCM and replace terminals if necessary. After repairs or replacing terminals, go to step 13). If terminals are okay, go to step 12).
  11. Replace Bank 1 HO2S 1. After replacing HO2S, go to step 13).
  12. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.
  13. Clear DTC(s) using scan tool. Start and warm engine to normal operating temperature. Using scan tool, select DTC, SPECIFIC, then enter DTC that was set. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If test did not run or failed, repeat step 2).
  14. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If other DTC(s) are displayed that have not been diagnosed, go to appropriate DTC.
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