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Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 12:05 am
by sdelasal
John, matthew, I'd suggest the following. Assuming a 0-5v range, and assuming that below 10% and above 90% are for diagnosing open circuit and closed circuit faults, then that gives a workable range of 0.5 to 4.5V. So closed throttle should be one of those values, depending on what way the sensor works with respect to the throttle. WOT should then be the other value. 3.8V is somwhere in the middle and not right for closed throttle. These voltages can be checked with engine off, ignition on.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 6:09 am
by xantia_v6
Some of the current symptoms are certainly puzzling.

One thing that might have been misinterpreted earlier is the split in the manifold sensor hose. An air leak hear will cause the sensor to see less vacuum and the ECU will add more fuel and the engine will run rich, not lean.

If the engine has run consistently rich for some time, the catalytic converter can have overheated, and could now be partially blocked.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 10:41 am
by xmexclusive
When the Lexia arrives it may be worth making reference checks on another V6.
I have mentioned ECU limp mode a few times so it may be worth giving examples:
Component malfunction - Butterfly position.
Values measured - outside tolerances.
Back up values used - Single fixed value used with minor adjustment for accelerator released or fully depressed.
Warning lamp - on.
So in this state visual position of the butterfly is no indication of ECU instruction to the engine.
I think that butterfly position has been used as a part of the fault finding analysis.
Component malfunction - Mixture richness.
Outside tolerances - Fixed value used.
Warning lamp on.

So it is effectively that the ECU has a "do its own thing" engine protection mode.
In that situation what will the Lexia read?
Not found an answer to that, I suspect it could be values read, the alternative is values used by the ECU.

Note that the Fenix 3B is unusual in that any glitch in the 12 volt feeds or earths to the ECU wipe all stored fault codes as does battery disconnection.
If the keypad immobiliser is fitted Citroen require it reset to 0000 (isolated) before any maintenance work is attempted.
This is to avoid inadvertent immobiliser lock out caused by component disturbance.

There is also the note about wrong wiring of oxygen sensors.
This can destroy them so correcting the wiring does not then repair the sensors.

John

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 10:43 am
by MTXM
Reading this makes me so grateful for my dull, boring, lethargic but reliable 2.0 Si!!!
The 2.0i is a nice motor Rob that also an ecu and all the same sensors to boot, so I do not think it is a specifically V6 problem! Regards, Matthew T.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 10:53 am
by MTXM
The spec is 0-5v linear over 0-6500rpm
Thank you for that John and just a brief update initially to confirm that I checked the throttle sensor with a meter and the range is 0.85-2.85v approx., which I think is acceptable and that might suggest the Lexia is fibbing!

I am also not convinced about there being an issue with the oxygen sensor, since after unplugging and substituting for a known good sensor fitted loose there was no change. The removal of the sensor also brought up the appropriate fault code.

In response to Mike I had expected a inlet manifold leak that apparently does cause a lean mix and then found the split pressure sensor pipe, which if resulting in a rich mix may have been the cause of the high oxygen sensor readings possibly? The disconnection was extremely brief so I think the cat will be fine.

With regards,

Matthew T.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 10:58 am
by MTXM
When the Lexia arrives it may be worth making reference checks on another V6.
I also thought that would a good idea John and I have at least two trouble free cars on which I can run checks!
With regards,
Matthew T.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 11:01 am
by Dean
You are right Matthew but with the 2.0i I find the fault finding process a lot easier on a wet and windy day if I can take a coffee and sit in front of the engine, usually on the front cross member and if the weather gets too foul, close the bonnet over myself, it makes life a little easier and more comfortable, I would have to be considerably slimmer to do the same with a V6, probably with weird alien like triple jointed fingers and arms.

D

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 11:03 am
by xmexclusive
Hi Matthew

According to the manual anything less than 4.5 volts on full throttle puts the ECU into limp mode.

John

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 12:17 pm
by MTXM
That is very interesting John and it certainly does feel like limp mode! I have just tried two other sensors and none will read above 3.3v, even when removed from the throttle, so what could cause the volt drop, other than a bad connection including an earth? The wires have continuity to the ecu and the ecu itself also appears to be good. With regards, Matthew T.

Re: S1 V6 auto back on the road at last!! - fourth time luck

Posted: Wed Feb 22, 2017 12:35 pm
by MTXM
I also meant to mention that I did this check following your earlier post John and the readings I obtained were around 4.85v and 0.8v, so not far off being correct. Regards, Matthew T.