Here's a couple of grabs of the lambda sensors on my X300.

Am I right in thinking the blue one looks a bit poorly? I will swap the sensors over after lunch and see if the fault follows the sensor.

Jonathan

ETA: One sensor was fitted April 2013 (to get through an MOT), the other was fitted January 2014. I haven't yet found out which is which.

 

Hi Jonathan,

Yes, you are correct! That blue trace definitely looks lazy - the sensor is not swinging high and low consistently.

I'm not sure how the ECM will respond to swapping the sensors. The ECM "adapts" to each sensor individually over time, and swapping the sensor connectors is known to cause problems, so you'll have to take that into consideration if the next chart looks funky.

Let us know what you find.

Cheers,

Don

 

Thanks for that. My understanding, based on talking to 'XJR' Andy, was that the ECU adapts fuelling in real-time based on lambda (and other) sensor readings, but it had no real memory to speak of. Or at least there's nothing you can do to reset it, but swap stuff around and let it figure it out. I may well have misunderstood - I'm fairly new to automotive engineering.

Anyway, now to find some crow's feet.

 

I've swapped the lambda sensors and the dodgy looking trace has followed the sensor.

New sensor on order, so fingers crossed.

PS: What an utter PITA they were - not helped by a pool of rain water on my garage floor right where I needed to lay. The top one wasn't so bad now I've got my new set of crows feet.

 

Hi theJPster,

Just for the record, here are some quotes from the AJ16 Engine Management System Dealer Training Publication:

Section 6 page 9

"Adaptive Idle Fuel Metering is used to allow for minor engine mechanical variability and engine ageing.

The ECM contains an adaptive idle fuel metering software function that automatically makes a baseline correction to the idle fuel metering strategy using long-term information from the oxygen sensors. The adaptation values are held in non-volatile memory (EEPROM) and will be retained even if the battery is disconnected."


Section 5 Page 7

"If the oxygen sensors are to be removed or the exhaust system replaced, the sensors and harness connectors must be labelled to ensure that they are installed in their original locations.

Oxygen Sensor Orientation
If the oxygen sensors are not installed in their original locations, the ECM can be reprogrammed using PDU to match the sensor locations to the ECM. This PDU routine is called Oxygen Sensor Orientation.

CAUTION:
When a new ECM or new sensors are installed or the wiring harness is changed, the ECM must be reprogrammed using PDU."


If I read this correctly, it appears that the ECM not only stores adaptation information for all four O2 sensors individually, but that this adaptation is sensitive enough to take into account the resistance of the wiring harness to each sensor.

I hope this offers some clarity on the issue.

Cheers,

Don

 

Don:
You are exactly right about what the manual says, and I believe you are also right about the reasons for re-orientation, but I know that many folks change the sensors without doing the orientation. I would guess that works OK because the oxygen sensor works in an almost binary fashion, with transitions between high and low state being more significant than either state's actual resistance reading.

The more significant purpose of the re-orientation is almost unbelievable- the lambda sensors do not have an absolute connection for bank A and bank B- it is determined by the orientation procedure and then stored in the ECU. That means that if you replace the ECU, there is a chance that either pre cat or post cat plug connections are stored in the opposite orientation. That leads to the controls on each channel "winding up", one high and one low trim.

 

I had that on my car. I bought it as a mostly non-runner. Turned out the PO had tried to jump start it after the battery went dead and he connected the booster cables to the wrong polarity. Took out the ECU and the AFM, but only randomly.

I bought a used ECU and the O2 sensors were oriented the opposite direction. I changed them so both ECU's were the same.

I'm more amazed that Jaguar used the same colour coded wire for all the sensors. It would have made so much more sense to have them all different.

 

Jagboi-
Actually, at least on some versions, the wire to the sensor plugs is different so you can identify which is which, That is way some folks do not believe that they did what they did! It amazes me too.

 

New lambda sensor fitted today. Idle was rough initially, but a brief run seems to have helped. My guess is that it took a run with the new sensor for it to adapt and home in on a reasonable air/fuel mix at idle.

 

Aaaaand it's running rough again.

Next step, scope the MAF. I've got one I can swap in, so that'll be a quick test.