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Home >> Isuzu >> 1998 >> Trooper S, Standard >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Tests W/Codes - 3.2L & 3.5L >> Self-Diagnostic Tests >> DTC P0154: Heated Oxygen Sensor (Ho2S) No. 1 Bank 2/Insufficient Activity >> Diagnostic Aids

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.

Using scan tool, monitor signal voltage while wiggling HO2S related connectors and wiring harness with a warm engine running at part throttle in closed loop. If a failure is induced, signal voltage will change from normal fluctuating voltage to a fixed voltage. A change in voltage will assist in isolating location of fault. DO NOT  solder HO2S wires.

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
  2. Start engine and allow it to reach normal operating temperature. Apply parking brake and increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, observe HO2S No. 1, bank 2 parameter. If reading is not 400-500 mV, turn engine off and go to next step. If reading is 400-500 mV, go to step 4).
  3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0154 is set, go to next step. If DTC P0154 is not set, check for an intermittent problem, see DIAGNOSTIC AIDS  .
  4. Inspect sensor harness for damage. Repair as necessary. If harness is okay, go to next step.
  5. Check for poor signal circuit (Red and White wires - 3.2L; Blue and Pink wires - 3.5L) at HO2S No. 1, bank 2 harness connector. Repair as necessary. Retest system. If circuit is okay, go to next step.
  6. Check for poor HO2S No. 1, bank 2 signal circuit (Red and White wires - 3.2L; Blue and Pink wires - 3.5L) at PCM harness connectors. Repair as necessary. Retest system. If circuit is okay, go to next step.
  7. Turn ignition off. Disconnect PCM connectors. Measure HO2S No. 1, bank 2 high signal circuit resistance between PCM and HO2S. If resistance is greater than 5 ohms, repair open or poor connection. Retest system. If wire is okay, go to next step.
  8. Measure HO2S No. 1, bank 2 low signal circuit resistance between PCM and HO2S. If resistance is greater than 5 ohms, repair open or poor connection. Retest system. If wire is 5 ohms or less, reconnect PCM connectors and go to next step.
  9. Disconnect HO2S No. 1, bank 2 connector. Turn ignition on. Connect fused jumper wire between ground and high and low signal circuits (Red and White wire) of HO2S No. 1, bank 2 (PCM side). If scan tool display is 0-10 mV, replace HO2S No. 1, bank 2. If scan tool display is not 0-10 mV, replace PCM. Retest system.
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