This little car has less than 6000 miles on it. Came to us after a period of inactivity. Puts engine, abs and tpms mil on after a couple of short drives. We have replaced the battery and O2 sensor no2, both with Bosch parts. Battery was tired after extended period flat.

Watching live data in graph form, primary sensor voltage cycles as expected, secondary gradually falls from 1.28V to zero and stays there as long as engine runs. Stall engine and voltage will rise again after a while.

Theory no1: Sensor is incorrect. Possible but correct cable length and connector, bosch part no 0258006721.
Genuine sensor has a supercession, over £200 so would like some confirmation this is the problem before spending that much!

Theory no2: It needs a software update. Local dealer is not very cooperative on these matters. Does anyone have the ability to check or know how to check?

Any other ideas?

Happy Christmas
Phil

Hi Phil

Bosch also lists 0258 030 310 for 02/14 onwards.

Have you confirmed if it is running lean?

Regards

Glyn

Hi Glynn. Post cat sensor is reading lean, pre cat is cycling correctly. Just noticed there is a flexible ball joint in pipe between cat and secondary sensor. Has evidence of a small leak. genuine seal on order.
Watch this space...
Phil

Exhaust seal replaced, no change.
Original sensor has Bosch part no, different from replacement.
Refitted original, functions but takes seven minutes to change voltage when hot after immediate restart, sets fault code for slow response.
Fit a new sensor with matching part number and repeat test, this one reacts after 12secs, does not read continuously lean.

Conclusions.
Pay more attention to part numbers. We relied on Factors reg lookup catalogue, Glyn's suggestion was correct number.
Spend more time confirming nature of fault and rectification.