2C7F - lambda probe after catalytic converter

[Thermaltake]

Had the engine warning light come on the other day.

Ran quickly through INPA which i had on an old laptop. Only 1 error was present which was 2C7F -lambda probe after catalytic converter 2 trim control

full error report:
Error: 1(1) Nr: 11391
type of error: 2
readiness flag: error-statur: MIL - Status:
MSV70 Fehlerspeicher lesen
2C7F Lambdasonde nach Katalysator 2, Trimmregelung (10) Abgas nach Katalysator zu mager
(16) Testbedingungen erfüllt
(33) Fehler momentan nicht vorhanden, OBD-entprellt
(49) Fehler wuerde das Aufleuchten der Warnlampe (MIL) verursachen
EndOfList

Unfortunately my INPA is only in german from what i can figure out. transalation:

exhaust after catalytic converter too lean
test conditions met
error currently not available
error would cause the warning lamp to light up

anyone any idea where to start looking before the 02 sensor itself? Car seemed to be driving fine although thinking back i may have noted some slight hesitation around 2500/3000rpm on occasion and MPG may be slightly down which could be related.

been doing some google but everyone else with this code seems to have some others to go along with it, I just have this 1 code. I seen something about an INPA 02 test but couldnt seem to find it or at least find it german or is it just checking the live data of the 02 sensors in which case i dont know what they should be.

Any help would be appreciated.

[colb]

Check for air leaks in the vaccum system for holes or splits that lets unmetered air into the system that is being picked up by the exhaust sensors as a lean mixture. Look at live data fuel trims of they are high it's a good indication for air leaks check all rubber and plastic pipes.

[Mike6]

My Lamda sensor lights have been coming on for a post cat. Hasnt made any difference to running of car although it is an MOT failure. All started when the new fuel was introduced but I doubt its related. One of the sensors is very hard to find on my 2005 E85 so I have been coding it out . My local friendly garage says the reason car has been running fine will be that the sensor itself will be fine, it will be the heater element which has gone.
After many months of searching this week I noticed that Autodoc have a few in stock so I have put in an order for both. Dont bother with the generic sensors where you have to cut and join cables and make sure you buy Bosch which I am told are BMW ones without the BMW packaging.

[Thermaltake]

Is anyone able to make sense of these readings? Annoying in half english/german. Not shown in the photos in the adaption page i was seeing lambda voltage after catalyst bank 1 around 0.87 while lamda boltage after catalyst bank2 was at 0.04 and bank 1 was jumping around a fair bit. All at idle.

Although the rough running page (filtered irregular running and 02-sensor-voltage) doesnt seem to paint a pretty picture.

RPM at idle was steady but was making some faint popping.

Details code was p114d, No other codes though which is strange as normally people seem to get multiple related codes where i only have 2c7f/p114d

[ThePocketGT]

I had the same code come up on mine, O2 sensor downstream of cat 2. There is limited information on what cause this and the N52 forum typically will respond with "blocked cats".

Mine went into a mechanic and he was unable to find the source of the problem and replaced the sensor, reset the code and all was good for a couple of miles.

In the end I decided to identify the fault myself and through process of elimination I found the following.
No vacuum leaks.
Endoscope on the cats both fine. I ran dpf/cat cleaner on both as a precaution.
Checked all spark plugs and replaced.
Test maf sensor, all OK.
Slight oil leak on the sump seal (common on engines over 100k).

Through process of elimination I had two more things to try and they were the VVT solenoids and vanos filters.

I wasnt able to check the VVT and Vanos filters due to my coupe being deemed a totalloss by the insurance company after an accident. I never actually found out if either of these was the cause of the problem, I suspected it was the VVT solenoids

Hope this helps

[Mike6]

Sorry, cannot translate that but my advice would be to get yourself one of the code readers in English. You will probably need it in future

[colb]

Post cat sensors will look preety staticin live data unless they react to high levels in the exhaust. The pre cat sensors should be producing a good rising and falling wave form as they range up and down thier voltage range.

[Thermaltake]

For any future readers coming across the same issue.

Took car to mechanic, He weirdly couldnt communicate with the o2 Sensor or clear the fault code on 2 different readers. He took all the o2 sensors out and gave them a good clean, After he took out and cleaned the affected o2 sensor (bank 2, post cat) the EML light extinguished itself and hasnt came back.

Car now feels alot better to drive. I suspect the car had been running lean on bank 2 for a while but not enough to trigger the lean running error code as the car now coasts a lot more freely off throttle and MPG has improved by a fair margin.

So if you get the 2c7f/p114d codes with no other identifying upstream codes, I would start straight away with the o2 sensor.

[Mike6]

I think you will need to get yourself the Creator fault finder. Not much money but really helps with diagnostics and resetting fault codes. When I reset mine the warning lights stay of for a bit but then come back for a post cat lambda sensor. Managed to get hold of the two sensors (not worth replacing one) from Autodoc but unfortunately despite my best efforts I cannot get under the car enough to reach them. Car runs fine and most probably the heater element inside the sensor playing up.

[Mike6]

Has anyone been able to replace the post cat lambda sensors other than from under the car. Having eventually got hold of the sensors I attempted to get access from under the car using trolley jacks and axle stands but there was simply not enough room to enable reasonable access to the sensors. I think I read somewhere that if you unbolted the heat shield near the steering rack then made a cut in the shield so that you could bend it up over the steering universal joint you could get to the sensors. Dont know whether this is true but I ask the question incase anyone has done this. Thanks