Lexia live data- how to interpret?

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discv
Posts: 46
Joined: 12 Jul 2017, 17:40
x 2

Lexia live data- how to interpret?

Post by discv » 10 Jun 2019, 13:07

Thought I would take the liberty of shifting my problem from the Citroen area to this sub forum.
My problem is an emissions failure on the C3 1.4i. My first hurdle was to get Lexia to play- but with invaluable help from Marc.......

So now I am collecting data. I know I am zoning in on the issue- but it is going to take time to learn how to interpret what I am seeing. I need help please!
This screen shot of the O2 sensors is trying to tell me something
SCR 01.JPG
Next stop[when the rain stops!] will be Fuel Trims
My head hurts trying to learn from this link-https://scanneranswers.com/read-live-da ... -fuel-trim

discv
Posts: 46
Joined: 12 Jul 2017, 17:40
x 2

Re: Lexia live data- how to interpret?

Post by discv » 12 Jun 2019, 13:38

So it’s a steep and rocky learning curve- and this is where I’m at. I think!
The graph above shows the two O2 sensors, one at each end of the cat.
The upstream one seems to be OK. The downstream one looks odd. My understanding is that curve should be a lot more flat
I think that the cat. is toast and therefore I might expect the curve of both sensors to be similar . The sensors are the same- I might try switching them.
My thinking is that I need to look closely at the fuelling. The fuel consumption is high, and I gather a rich mix kills cats.
The odd thing is I have not seem the MIL light up.
None of these ramblings are definitive! But perhaps other members might throw some ideas into the mix.

discv
Posts: 46
Joined: 12 Jul 2017, 17:40
x 2

Re: Lexia live data- how to interpret?

Post by discv » 14 Jun 2019, 11:46

So now I am taking a look at the MAP sensor. This is the sensor on the intake manifold that measures air pressure.
SCR003.JPG
I cannot make sense of it. The ambient air pressure where I am is around 1010 Mb.
I would have expected the 'reference pressure' to be around what the real pressure is.
The first 5 secs. are with the engine not running, so the air pressure in the manifold must surely be the same as on the outside?

discv
Posts: 46
Joined: 12 Jul 2017, 17:40
x 2

Re: Lexia live data- how to interpret?

Post by discv » 14 Jun 2019, 16:09

Today I unplugged the Map sensor, and ran the engine. This did not cause the MIL to come on, but it did store up the expected codes.
I then went on to have a look at a couple of things I have been noticing in diagnostics i.e throttle track 1 has been showing zero voltage, and engine status has being showing 'idle'- regardless of rpm. See here;
SCR004.JPG