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Dave1392 04-30-2013 08:33 AM

O2 Sensor Bank 1 Sensor 2
My daughter purchased a 2005 Jeep Liberty and loves it. About a month ago she recevied an O2 sensor (P0038) code. I replaced the sensor and all was good until a few days ago. The same error code is back. I replaced the O2 sensor again but this time it will not clear. I checked the connector at the O2 sensor and I am not getting 12 volts to the heater circuit. Is there a fuse or relay that feeds the O2 sensor? If so which one is it?

Frango100 04-30-2013 09:36 AM

Re: O2 Sensor Bank 1 Sensor 2
Welcome to the garage.
For sure there is a fuse for the O2 heaters. Not familiar with the liberty, but some jeeps even have a relay in the heater circuit. Have a look in the power distribution center (relay/fuse box under the hood), you will see on the inside of the cover which relay and which fuse is for what. Did you use original sensor ( also not sure for the liberty, but on the WJ its Denso), because other brands may give problems with slow heating and the PCM sees this as a heater fault.

Dave1392 04-30-2013 09:40 AM

Re: O2 Sensor Bank 1 Sensor 2
I did look (last night) and didn't see anything that refered to O2 sensor. I'll check again today when I can see better. Thanks

Frango100 04-30-2013 09:50 AM

Re: O2 Sensor Bank 1 Sensor 2
Also depending on emission package, the O2 heaters are fed via the auto shutdown relay. This relay falls off after some seconds when the PCM sees that the engine is not running. In that case you will not have the 12V at the connector. But did you use original sensor?

Dave1392 04-30-2013 10:32 AM

Re: O2 Sensor Bank 1 Sensor 2
I used a Bosch sensor.

Dave1392 04-30-2013 10:54 AM

Re: O2 Sensor Bank 1 Sensor 2
I used the same Bosch O2 sensor on Bank 2 Sensor 2 without any issues.

Frango100 04-30-2013 05:35 PM

Re: O2 Sensor Bank 1 Sensor 2
The Bosch sensors are very good, but they heat up more slowly then the Denso sensors. If the heating takes too long, the PCM will see it as a fault and set a fault code and switch the check engine light on. I have heard of more guys who used Bosch without problems, but also many others who encountered problems with the Bosch sensors. This is normally solved by using the original Denso sensors.

Dave1392 04-30-2013 05:59 PM

Re: O2 Sensor Bank 1 Sensor 2
Thanks for the input. I still don't have 12 volts at the connector to the O2 sensor. The dealer told me that the PCM module feeds the 12 volts to the sensor, it is not fused or run through a relay.

Frango100 04-30-2013 06:33 PM

Re: O2 Sensor Bank 1 Sensor 2
I don't have schematic manual for the liberty, so can't confirm this. But it would be strange that the PCM would.continue feeding the heaters when the engine doesn't run. On my jeep its also the PCM who switches the heaters, but via the auto shutdown relay. Maybe a member with Liberty wiring schematic could confirm the way its wired.

Silly02Jeep 10-26-2013 06:47 PM

Re: O2 Sensor Bank 1 Sensor 2
I'm looking at a wiring diagram for the '02 Liberty and there is a oxygen sensor downstream relay in the PDC in the '02 model, but both rear O2's are being feed off of the same circuit; so if you have power at the 2/2 but not at the 1/2 then look for a wiring issue.

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