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Home >> Isuzu >> 1996 >> Trooper LS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0161 - Ho2S No. 2 Bank 2/Heater Circuit (A/T Only)

DTC P0161 - Ho2S No. 2 Bank 2/Heater Circuit (A/T Only)

NOTE: ALWAYS inspect a faulty HO2S for contamination and correct cause before installing a new HO2S.
  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
  2. Allow engine to cool. Turn ignition on. Observe HO2S No. 2, bank 2 parameter on scan tool. If display is greater than 650 mV or less than 250 mV, check for an intermittent problem. See TESTS W/O CODES article. If display is not as specified, go to next step.
  3. Inspect HO2S heater fuse (20-amp) in engine compartment fuse box. If fuse is blown, check for short circuit and replace fuse. Retest system. If fuse is okay, go to next step.
  4. Turn ignition off. Raise and support vehicle. Disconnect HO2S No. 2, bank 2 harness connector. Turn ignition on. Using a test light connected to ground, probe HO2S No. 2, bank 2 ignition feed circuit at connector (PCM side). If test light comes on, go to next step. If test light does not come on, go to step 7).
  5. Connect test light between ignition feed circuit and heater ground circuit at connector (PCM side). If test light comes on, go to next step. If test light does not come on, go to step 8).
  6. Turn ignition off. Ensure HO2S No. 2 is cool. Using an ohmmeter, measure resistance between ignition feed circuit and heater ground circuit at HO2S No. 2 harness connector (sensor side). If resistance is 3-6 ohms, go to step 9). If resistance is not as specified, go to step 10).
  7. Repair open in HO2S No. 2 ignition feed circuit. Retest system.
  8. Repair open in HO2S No. 2 ground circuit. Retest system.
  9. Check for poor connection at HO2S No. 2, bank 2 harness terminals. Repair as necessary. Retest system. If harness is okay, go to next step.
  10. Check for poor connection at HO2S No. 2, bank 2 high or low circuit terminal connections at harness connector. Repair as necessary. Retest system. If connections are okay, go to next step.
  11. Turn ignition off. Disconnect PCM harness connector terminals. Using an ohmmeter, measure resistance of HO2S No. 2, bank 2 high and low signal circuits at PCM harness connector. If either circuit resistance is greater than 5 ohms, check for an open or poor connection. Repair as necessary. If wires are okay, go to next step.
  12. Check for poor HO2S No. 2, bank 2 terminal connections at PCM. Repair as necessary. If connections are okay, replace HO2S No. 2, bank 2. Retest system.
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