2006 TJ O2 sensor issue P0161

A Fangless Wolf

A Fangless Wolf

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Chesterton, IN
This has been such a weird week. after getting rejected for a smog test, 02 heater circuit not ready, no CEL. I scheduled an appointment with the local dealer for a TSB about that exact issue. Then a few days later after replacing brakes, CEL comes on for bank 2 sensor 2 faulty heater circuit.
Threw a new sensor in (walker) still throws the same code. Took it in to the dealer and they say it's the sensor, they said anything but oem will cause problems. So I put a NTK in this afternoon. Also pinned out the harness between the sensor plug and PCM. Everything pinned out fine. Not sure what else could be causing this issue with the downstream 02 sensor heater circuit. Any ideas would be appreciated

06 TJ 4.0L
 
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A Fangless Wolf said:
i really hope not, but ill keep it in mind
Click to expand...

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I think You're still in stage 1... Do a little reading on here about 05 06 PCM before throwing more parts at it.
 
The PCMs are a known problem. Not a matter of if, but when it will fail. My 06 LJ auto already has a aftermarket OEM replacement that I am replacing with a new one. My 06 TJ with 135K miles stick has given me zero trouble but knowing it also is failure prone it will be getting replaced. The auto's are a known problem but only recently did I realize the manuals also have failures.

Both replacements will be from @Wranglerfix Its the only way to go and they are great!
 
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Is there any way to test the pcm before just throwing parts at it?

Went for a drive and bank 2 sensor 2 is sticking at 1.3v way longer than bank 1. Dealer wants to replace the harness to bank 2 already due to a broken connector. I'm still hopeful it's just a damaged wire thats making intermittent contact.
 
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A Fangless Wolf said:
Is there any way to test the pcm before just throwing parts at it?

Went for a drive and bank 2 sensor 2 is sticking at 1.3v way longer than bank 1. Dealer wants to replace the harness to bank 2 already due to a broken connector. I'm still hopeful it's just a damaged wire thats making intermittent contact.
Click to expand...

Ways of verifying heater circuit function without sending it off.

1.) Graph O2 with scan tool. Start vehicle. With it in open loop, the PCM should activate the 02 heater via duty cycle. The cold/open loop bias voltage should drop drastically the moment the vehicle is started.

2.) Scope the heater circuit. Either watch for the same 12 volt duty cycle when in open loop, or, force the heater circuit on via bi-directional control.

I'm annoyingly against blindly loading the parts cannon, but in this particular instance you're more than able to assume your PCM is faulty so long as you've verified circuit integrity. It is as common an issue as they come and @Wranglerfix will be the route you should take.
 
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Did a pcm reset this morning but doesn't seem to have resolved the issue. Other than pcm being bad, is there anything else that will cause the heater circuit to stay at 1.3v? Dirty sensor maybe? Want to try other avenues before throwing money at it.
Red: bank 1 sensor 1
Blue: bank 2 sensor 1
Green: bank 1 sensor 2
pink: bank 2 sensor 2

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A Fangless Wolf said:
Just had the realization, it's staying at 1.3 because the heater isn't warming the sensor. Once the engine is at temp it starts working properly.
Click to expand...

That's correct.

The voltage you're seeing on pin 10 is a PWM or Duty cycle. If you're looking at that voltage with a standard multimeter, the reading is essentially useless. You need a scope or a graphing multi-meter to see it.

However.... it is interesting that you saw any voltage there at all.

Have you verified sensor ground integrity?

If not,

With Key off/Engine off:
1.) Unplug o2 sensor.
2.) With an incandescent light connected to battery positive, gently touch pin #2 (Black/Light Blue wire).
3.) Test light should light.

4.) IF it doesn't light, plug sensor back in, back probe the same wire with a T-Pin, and give it a ground. Problem should resolve itself. Repair faulty ground located at G105 (right rear of engine block).
 
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ItchyDong said:
That's correct.

The voltage you're seeing on pin 10 is a PWM or Duty cycle. If you're looking at that voltage with a standard multimeter, the reading is essentially useless. You need a scope or a graphing multi-meter to see it.

However.... it is interesting that you saw any voltage there at all.

Have you verified sensor ground integrity?

If not,

With Key off/Engine off:
1.) Unplug o2 sensor.
2.) With an incandescent light connected to battery positive, gently touch pin #2 (Black/Light Blue wire).
3.) Test light should light.

4.) IF it doesn't light, plug sensor back in, back probe the same wire with a T-Pin, and give it a ground. Problem should resolve itself. Repair faulty ground located at G105 (right rear of engine block).
Click to expand...

Grounds good, but I did notice when I touched the pin 1 the light would flash briefly. Traced it back up and when I touch c3 pin 10 on pcm side it will flash briefly.

Wiring seems fine as when I probed c3 pin 10 test light illuminated and ohmes read correctly with sensor plugged in. Seems the only thing left is the pcm itself.
 
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A Fangless Wolf said:
Grounds good, but I did notice when I touched the pin 1 the light would flash briefly. Traced it back up and when I touch c3 pin 10 on pcm side it will flash briefly.

Wiring seems fine as when I probed c3 pin 10 test light illuminated and ohmes read correctly with sensor plugged in. Seems the only thing left is the pcm itself.
Click to expand...
The light is flashing because you're seeing the duty cycle. Chrysler products are inherently picky with the o2 sensor heater circuit. I'm a big fan of testing with a light, but testing the duty cycle of the o2 heater circuit with a light is almost useless on the Jeep because it's pulling so few amps that the PCM shuts it down. Which, leaves the troubleshooter wondering... is this momentary blip I'm seeing via test light the problem, or am I creating a problem and the PCM is shutting off the driver as programmed in response to my low amperage test light.

Again, the only way to perfectly see this is by means of a graphing multimeter or oscilloscope in open loop and via bi-directional control.

I will say this... I don't have warm and fuzzies about you're PCM being the issue at this point.

Before I pulled the trigger on it, I'd swap B1S2 and B2S2 (both downstream sensors) plugs around by running jumpers from one to the other, and graph the COLD O2 sensors in open loop while watching that same bias voltage. If the problem stays the same, assuming all of your wiring checks were done correctly, it's the PCM. If it follows the swap, you've got a bad brand new sensor.

P.S. Stop back probing the PCM at pin 10. It's incredibly easy to accidently jump 12 volts to a pin that shouldn't see battery voltage.
 
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ItchyDong said:
The light is flashing because you're seeing the duty cycle. Chrysler products are inherently picky with the o2 sensor heater circuit. I'm a big fan of testing with a light, but testing the duty cycle of the o2 heater circuit with a light is almost useless on the Jeep because it's pulling so few amps that the PCM shuts it down. Which, leaves the troubleshooter wondering... is this momentary blip I'm seeing via test light the problem, or am I creating a problem and the PCM is shutting off the driver as programmed in response to my low amperage test light.

Again, the only way to perfectly see this is by means of a graphing multimeter or oscilloscope in open loop and via bi-directional control.

I will say this... I don't have warm and fuzzies about you're PCM being the issue at this point.

Before I pulled the trigger on it, I'd swap B1S2 and B2S2 (both downstream sensors) plugs around by running jumpers from one to the other, and graph the COLD O2 sensors in open loop while watching that same bias voltage. If the problem stays the same, assuming all of your wiring checks were done correctly, it's the PCM. If it follows the swap, you've got a bad brand new sensor.

P.S. Stop back probing the PCM at pin 10. It's incredibly easy to accidently jump 12 volts to a pin that shouldn't see battery voltage.
Click to expand...
not sure how it would be showing a duty cycle with the key off but im also out of my element with this issue.
either way, i think im at the end of what i can do. ill probably be sending my pcm off to @Wranglerfix next week and just have them test it.
 
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