I have a 2008 Cooper S with 95K miles that I've owned for about 2 months. Check engine light came on a few weeks ago with downstream O2 sensor code P0141 for the heated circuit. I replaced the number 2 sensor with a cheap $28 aftermarket Chinese one after the Dealer wanted to charge me $379. CEL went out for a few days, then the car started idling badly and stalled backing out of the driveway. Got it restarted, ran OK then CEL came back on with multiple codes for rich idle, misfires and the same O2 sensor code. I suspected the cheap aftermarket sensor, bought a new Bosch OE sensor and installed it with the same result. CEL will not go out. Runs seemingly OK but does hunt at idle slightly. Seems to be running rich. I re-checked the connection at the connector, all seems good and clean. Help!!! I'd love to save spending hundreds at the dealer... Any ideas?

 

2009 MCS

FWIW - I was advised to always replace both O2 sensors (upstream and down-stream) at same time when getting a O2 sensor related CEL.

When i replaced mine, I used a Bosh one for upstream, and a NTK one for down-stream, ordered from rockauto

Good luck,

W

 

CEL will only go out after so many warm up cycles with the error absent. You can use an OBD2 code reader/data viewer/logger to erase the code, which should extinguish the CEL but the code is probably permanent which just means it can only be erased by the engine controller after so many warm up cycles with the error condition absent.

For the other symptoms you can use the code reader's data viewer feature to view real time engine telemetry.

The symptoms may be sensor related. O2 sensors can fail at any time. I had some fail at less than 95K miles. Even if they do not get bad enough to trigger a CEL they can degrade and engine performance suffers.

My SOP is unless a new sensor fails if any sensor fails due to "old age" and 95K miles qualifies as "old age", I replace all sensors at the same time.

But you can check for a abnormal MAF reading (if of course the engine uses a MAF). If not then there will be a MAP reading or something that lets the engine controller know how much air the engine is using at any time and thus let the engine controller supply the proper amount of fuel.

You can check the intake air temperature to see if it is reasonable. And you can check the coolant temperature. I had a VW that developed some engine problems, not severe but I can't recall the details now, but which I suspected were due to a malfunctioning coolant temperature sensor. Upon observation it was reading low and I had it replaced and symptoms went away.

 

Just replaced the upstream O2 sensor with OE Bosch.... CEL will not relent. Still shows P0141 O2 heater circuit. Stalls occasionally at idle, running rich. I've replaced 3 O2 sensors, so the problem is somewhere else despite the code. Any ideas?

 

Hello,

After replacing O2 sensors, did you clear the CEL with an appropriate scan tool?

Might be worth a try, to disconnect battery for 5min also...

Good luck.

W

 

I did erase the codes with my scanner, but CEL comes back on immediately when the car is started again.

 

Checked (pulled) a couple of engine compartment fuses, and now I have new codes: P0B49 Hybrid battery voltage sense "C" Circuit intermittent/erratic, and P0602 Powertrain Control Module Programming Error. Maybe I pulled the ECU fuse???!!! did it reset or something? ARRRGGGHHHHHHH

 

Update: I took the car to a local garage where it stayed for 3 days getting checked out. They erased the codes, and said there were no issues. They even performed a smoke test to ensure the intake was not leaking anywhere. Car was fine for 3 weeks with no CEL, now has CEL back on and the SAME CODE AGAIN. Number 2 O2 Sensor, heated circuit. Car idles a little rough and has stalled a few times. Seems OK otherwise. Both O2 sensors are brand new Bosch. What else can cause this P0141 code?

 

Are you also getting a P0136 Code along with the P0141?

 

I have the same issue with a 2013 S model. did you find a solution?

 

i am. just pulled codes- got 0030, 0136 and 0141.