O2 SENSOR ON 98 RODEO

  • Tiny
  • dirt1962
  • 1998 Isuzu Rodeo
  • 6 CYL
  • 4WD
  • automatic
  • 189,432 miles

I replaced the rear passenger O2 sensor with a dealer O2 sensor in my 98 Isuzu Rodeo, disconnected the battery for 30 minutes, drove the car ~100 miles, the light came back on. Disconnected the battery for 12 hours, drove >200 miles, the check engine light came back on. Is it possible the catalytic converter is shot? The car has >189K miles on it and still runs strong, but I can't get it throughinspection with the check engine light on. Do both battery terminals need to be disconnected - I only disconnected the ground.(Seems like a dumb question, but I'm out of ideas). I'm thinking of bringing the car into the dealer to have them clear the error message/code.

Thursday, February 3rd, 2011 AT 4:53 PM

7 Answers

  • Tiny
  • KHLow2008
  • Expert
  • 41,938 posts

Get a scan done and let me know the EXACT trouble code. Most parts stores provides free scanning services.

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Wednesday, February 9th, 2011 AT 4:36 PM
  • Tiny
  • dirt1962
  • Member

P0161 - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 2

I had put an aftermarket sensor in prior to the dealer one, and had gotten the same error message. I have cleared the error code 3 times now, check engine light keeps coming on. I was told I may have been sold a bad sensor from the dealer as well. Is it really that common? Is it possible the catalytic converter is bad, or is that error code specific to a O2 sensor failure? What is your suggested course of action? Thank you for your time.

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Tuesday, August 23rd, 2011 AT 10:13 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,938 posts

I believe you have replaced the wrong sensor.

Bank 2 refers to left cylinder bank, meaning driver side and is it is the one rear of left catalytic converter.

DTC P0161 : HEATED OXYGEN SENSOR (HO2S) NO. 2 BANK 2/HEATER CIRCUIT

NOTE: ALWAYS inspect a faulty HO2S for contamination and correct cause before installing a new HO2S. Bank 2 refers to left cylinder bank.

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. If DTC cannot be duplicated,
check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. Go to next step.

2. Allow engine to cool. Disconnect fuel pump relay. On 3.2L, connect fused jumper between fuel pump relay socket positive battery terminal No. 5 (White/Black wire) and relay wire that goes to fuel pump and HO2S fuses (Black/Red wire). On 3.5L, connect fused jumper between fuel pump relay socket positive battery terminal No. 4 (White wire) and relay wire that goes to fuel pump and HO2S fuses (Red wire). On all models, turn ignition off. Install scan tool. Turn ignition on. Observe HO2S No. 2, bank 2 parameter on scan tool for several minutes. If display is greater than 650 mV or less than 250 mV, check for an intermittent problem, see DIAGNOSTIC AIDS. If display is not greater
than 650 mV or less than 250 mV, go to next step.

3. Inspect HO2S heater fuse (20-amp) in engine compartment fuse box. If fuse is blown, check for short in 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. Connect test light between ground and ignition feed circuit (Red/Blue wire - 3.2L; Red/White wire - 3.5L) 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 (Red/Blue wire -
3.2L; Red/White wire - 3.5L) and ground circuit (Black wire) 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. Measure resistance between ignition feed circuit (Red/Blue wire - 3.2L; Red/White wire - 3.5L) and heater ground circuit (Black wire) at HO2S No. 2 harness connector (sensor side). If resistance is 3-6 ohms, go to step 9). If resistance is not 3-6 ohms, go to step 10).

7. Repair open in HO2S No. 2 ignition feed circuit (Red/Blue wire -
3.2L; Red/White wire - 3.5L). Retest system.

8. Repair open in HO2S No. 2 ground circuit (Black wire). 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. Measure resistance of HO2S No. 2, bank 2 high and low signal circuits (White/Blue and Orange/Blue wires - 3.2L; Blue and Green wires -
3.5L) 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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Tuesday, August 23rd, 2011 AT 10:49 PM
  • Tiny
  • dirt1962
  • Member

Oh my. That's both a relief and a drag. I have been wasting all this time because I was told bank 2 was the passenger side. I never even considered something so basic could be the issue. I'll get another sensor, and swap it out. Thank you SO much for your help. Unreal. I'll let you know how it goes. Have a great night.

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Wednesday, August 24th, 2011 AT 1:05 AM
  • Tiny
  • KHLow2008
  • Expert
  • 41,938 posts

You're welcome.

Have a nice day.

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Wednesday, August 24th, 2011 AT 11:59 AM
  • Tiny
  • dirt1962
  • Member

Well, it's been a month and the check engine light has never come back on. You have been a huge help. Thank you very much, have a great weekend.

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Saturday, September 24th, 2011 AT 3:30 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,938 posts

You're welcome and thanks for the feedback.

Have a great weekend.

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Sunday, September 25th, 2011 AT 6:31 AM

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