Lexia data interpretation help needed! (Mot failure on emissions)

New to your forum, having had various Citroens in the family for years, this is the first C3.

My problems started with a Mot failure on emissions. Having the good fortune to own Lexia I was not too worried. But......! The ambient pressure around these parts is circa 1010 Mbar. So I would expect the reference to be at that figure, and with the engine not running (first 5 secs.) the manifold to be showing that same sort of reading. No apparent output from Throttle track 1, engine shown as at idle even though Rpm can be seen.

Believe me, I have not a clue what I am talking about! But I aim to learn- being an old and disabled geezer garages just take the.......
My track record- I have just finished a 1.6Hdi rebuild. It took me a year crawling round the front garden- and it runs like a dream.

discv wrote: ↑Fri Jun 14, 2019 4:00 pm My problems started with a Mot failure on emissions. .

Hi discv

Did you get a printout of the emissions or something to indicate what is wrong with the emissions?

Do you have the MOT history of the car? I am wondering if the emissions have been an ongoing problem..

discv wrote: ↑Fri Jun 14, 2019 4:00 pm No apparent output from Throttle track 1, engine shown as at idle even though Rpm can be seen.

Are there any P codes stored?

"Did you get a printout of the emissions or something to indicate what is wrong with the emissions?"
No. The tester was concerned about his machine!

"Do you have the MOT history of the car? I am wondering if the emissions have been an ongoing problem.."
This I am looking into- but I suspect there is history.

"Are there any P codes stored?"
There were dozens. Mostly relating to the brake pedal switch. I cleared them all- and now just get the brake switch coming up occasionally.
But I noticed that the Mil did not come up. The Mil is working at ignition on. So I unplugged the Map sensor, ran the engine, the Mil did not come on but the expected codes got stored.

I'm now thinking I am chasing my tail! Beginning to think I have a ecu/water issue.

I can find no history of emission problems with this car- but we all know there are ways round everything!
I've had all the electrical plugs off the ECU and the engine fuse box. I've also pulled off and inspected every other connection in the area.
There is no sign of water anywhere [ or any other discolouration] Everything has been put back with lots of Vaseline.

Where next? That flat line on the track 1 voltage + the engine status being reported as 'idle' despite being at 2k rpm looks like it deserves focus of attention

discv wrote: ↑Sun Jun 16, 2019 5:05 pm Where next? That flat line on the track 1 voltage + the engine status being reported as 'idle' despite being at 2k rpm looks like it deserves focus of attention

Is the MOT your concern or the strange readings from Lexia?

You say you have error codes stored. It would be worth fixing the codes you have left after doing the delete/re-read thing* as these are ones that the computer thinks is important enough to present to the one reading them.

* read the codes, make a note of them, delete the codes, run the car again, then re-read the most recent or permanent ones.

This gives you a historical perspective and a current 'most wanted' list.

discv wrote: ↑Sat Jun 15, 2019 10:25 am No. The tester was concerned about his machine!

It will be difficult to know what to fix if we don't know what is out of spec.

Some of these lexia readings don't work because the version of lexia is too low for the car, makes sense as old lexia would never know about the workings of a new car without an update.

"Is the MOT your concern or the strange readings from Lexia?"
The emissions and the high fuel consumption are the primary concern

"You say you have error codes stored."
I cleared the old codes, and the only codes that come up now relate to the brake switch [part on the way] and the Map open circuit- which I know about because I unplugged it!
But the MIl does not seem to trigger. And no code is getting stored for faults that I think are present. i.e the flat line on track 1

"It will be difficult to know what to fix if we don't know what is out of spec."
True- this is probably the best next stop

"Some of these lexia readings don't work because the version of lexia is too low for the car,"
The car is a 2007 build and I am running lexia 7.02 which is valid for cars up to 2009.

I appreciate your input on this one- no one else will discuss my problem- not even French Cars forum experts!

discv wrote: ↑Sun Jun 16, 2019 6:08 pm But the MIl does not seem to trigger. And no code is getting stored for faults that I think are present. i.e the flat line on track 1

The MIL doesn't always trigger for all faults, all engine faults or even when you would *expect* it to be on, so don't worry about that.

Track1 of the throttle measurement sounds like part of the feedback loop of the throttle body butterfly valve. The ECU says to the throttle body to 'open' and the feedback loop reports back to the ECU that it has actually opened.
The signal from the throttle pedal goes to the ECU and this decides how much to open the butterfly throttle body by.

The throttle body 'tracks' that feedback the signal can be investigated, maybe swapping parts (throttle body) to confirm?

There is also an electronic accelerator pedal and this has a twin track for dual signals that are a form of cross-checking for signals that concur. The TPS signal passed through a plug only found in the RHD models due to the design conversion from LHD and that plug gives problems. This topic covers the fix but I would expect error codes stored related to this.

Useful stuff Arfur, thank you. That's tomorrows agenda sorted!