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[arthill]

Hi all

Had car serviced last week also had oil and ATF changed. THe MIL had come back on after being off since fitting MAF, O2 post cat sensor was found to be incorrectly fitted, after correcting this no faults were present and no MIL. it stayed out untill yesterday, had ECU read today can't remember exact code mechanic told me it was the O2 sensor (post cat bank 2 ) Emissions test last week were fine, he said this would rule out cat, Car is still running well, only this light coming on, would replacing this sort problem, or could something else be causing this sensor to play up. :-/  

[Dazzler]

A good garage should actually be able to SEE what the Lamda sensor is reading as well as just reading the code.
This would tell you the sensor is faulty or not.

[arthill]

Going back into garage tomorow, they were very busy monday and could only do a quick read of ecu. I believe post cat sensor is to report on operation of cat, mechanic said since emissions were fine cat is ok. I wondered if there is something else that could affect sensor without affecting performance, he switched MIL out monday and still out but for how long.?

[Big_Mart]

Hi all

Had car serviced last week also had oil and ATF changed. THe MIL had come back on after being off since fitting MAF, O2 post cat sensor was found to be incorrectly fitted, after correcting this no faults were present and no MIL. it stayed out untill yesterday, had ECU read today can't remember exact code mechanic told me it was the O2 sensor (post cat bank 2 ) Emissions test last week were fine, he said this would rule out cat, Car is still running well, only this light coming on, would replacing this sort problem, or could something else be causing this sensor to play up. :-/  

How can a 02 sensor be fitted incorrectly? was the plug in the exhaust and the sensor rammed into the plug

[Kevin Wood]

This sounds very similar to the problem that keeps occurring on the 3.2.

If the setup is similar, the post cat sensor is after a small "first stage" cat but before the main cat. For some reason, this sensor appears to be troublesome but, even if the emissions after the first stage cat are problematic, the main cat clears the emissions up so they are within the MOT limits.

I have had this problem crop up a few times on my 3.2, as have a number of members, but AFAIK it's not common on a 2.2.

The theory is that the first stage cat is a little small to handle the flow of the 3.2 engine and hence doesn't clear up the emissions adequately. Once this has happened a few times the light comes on, and it will clear if the emissions remain OK for a certain number of engine start/stop cycles.

The problem is unlikely to be a faulty lambda sensor. Some members have reported that a dose of "cataclean" stops the fault recurring and I would be inclined to try this as a next step, followed by clearing the codes and seeing if the light stays off.

If this doesn't work, and bearing in mind that it's not a common problem on the 2.2, cleaning (in an ultrasonic bath) or replacing the post cat sensor might be worth a try.

As with all such problems, make sure the inlet, and exhast system upstream of the sensor have no leaks.

Kevin

[arthill]

Thanks for replies , will investigate tomorrow and report back.
  

  John