What's this Lexia error?

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Mandrake
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Re: What's this Lexia error?

Post by Mandrake »

The waste gate is controlled by the ECU on the 2.0 TCT, so I'm assuming that error means that the ECU is not happy with the boost pressure reading its getting when trying to regulate the boost pressure...

Will the Lexia show you the measured boost pressure in the parameters measurement section ? Looking at that while revving or driving the car may shed some light on the issue. It could potentially either be a fault with the pressure sensor causing a false pressure reading, or alternatively something causing the boost pressure to actually be wrong.
Simon

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Re: What's this Lexia error?

Post by Mandrake »

Mike - I got no emissions sheet with my MOT a few weeks ago either, when I phoned back and asked for it they posted it out for free, but in a way I wish I hadn't got it as it only passed the CO test by the skin of its teeth, and had probably been "fudged" through the test! :? (Sometimes ignorance is bliss)

Either things have changed since last year and you no longer get an emissions result sheet as standard, or perhaps like me yours was a very marginal pass that had a helping hand which they through was best left unsaid...

Fluctuating brake I haven't had before but I'd assume that would be a warped or otherwise non-uniform disc surface.

As far as your boost problem goes the reading will come from the MAP sensor but on a turbo you'll have a special high pressure MAP sensor.

A non-turbo engine MAP sensor only reads up to just over 1 bar (absolute) as it only has to read between full vacuum and atmospheric pressure, or up to about 1050 millibars.

A turbo engine measures boost relative to atmospheric pressure so if you have a maximum "boost" of 1 bar then the pressure in the manifold is 1 bar plus whatever atmospheric is, eg about 2 bars absolute.

As I said earlier, the first thing I'd do is put the Lexia on the car and monitor the MAP reading under parameters measurement and see if its giving a sensible reading. With the key on but engine not running it should read ambient atmospheric pressure which is a good first check. (Compare the millibar reading to your local weather report! :) But remember it will drop with altitude increase above sea level...most weather report millibar readings are normalised to sea level even if the weather station is above sea level)

Under load while driving the pressure should go above atmospheric so should be somewhere between 1000 and 2000 millibars, as I think the maximum boost of the TCT is about 1 bar at low rpm falling off at higher rpm. (Anyone know actual figures for the boost curve?)
Simon

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Re: What's this Lexia error?

Post by KevMayer »

This brings back memories for me.

On an 2.0 TCT the engine management light will come on if you have overboost.
Is your EML on all the time? If it only comes on under load then it will be due to overboost. This will be due to a leak on the pipe/Solenoid/pipe from your inlet manifold to the waste gate controller on the turbo. If this pipe is split, say, there'd be no pressure feed to the waste gate control diaphragm and so the waste gate would remain closed and you'd have no boost control. When you put your foot down the EML would light up.

If your EML is on all the time, even on tickover, then there's a different problem.
Cheers, Kev

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Re: What's this Lexia error?

Post by KevMayer »

Could you have a boost leak?

Do you get loud hissing noises?

Could the intercooler be split or a hose split or loose?
Cheers, Kev

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Used to have:- Xantia 1.9 TurboD SX. 1996 Blue & 1998 Silver Activa. + 1992 BX TZD Turbo.
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Post by addo »

I'd say it's a blocked exhaust.

No, seriously, first check the battery cables, then the ignition amplifier, then the tachymetric relay.
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Re: What's this Lexia error?

Post by Mandrake »

Can you not get a few of your pals to help you push the car out of the way to free the V6 ? :twisted: I've pushed my V6 by myself on occasion while in the middle of doing work that won't allow me to start the engine, albeit on level ground. Two or three guys shouldn't be a problem unless you have a steep drive...
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Re: What's this Lexia error?

Post by Mandrake »

I'd start by measuring the voltage on the starter solenoid terminal on the starter while someone turns the key. If the voltage appears as it should in the start position give the starter a whack with the end of the wheel brace in case its worn brushes...

Is there not even a click from the starter or any of the relays in the under bonnet fuse box when turning to start ? If you post the RPO number and engine/gearbox/body type of the car I'll see if I can dig up some starter wiring diagrams for you tonight.

Edit: Another obvious thing you should check - measure the battery voltage directly at the battery while someone turns the key to the start position. What do you get ? If its below about 10 volts in the start position you might just have a flat or faulty battery...
Simon

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Re: What's this Lexia error?

Post by Mandrake »

The immobiliser system has nothing at all to do with the starter - the starter will still turn the engine over on an immobilised car, so don't worry about what the immobiliser says until you have the starter ticking over.

For the starter not to work it has to be a basic electrical fault:

* Flat battery
* Faulty battery
* Faulty wiring
* Blown fuse
* Faulty relay (if any are involved)
* Faulty starter solenoid
* Faulty ignition switch
* Faulty starter motor (brushes etc)

That's about all the possibilities really, ECU is nowhere in that list. (At least on a Xantia :) )

Batteries can die (as in faulty) suddenly and without warning so just because it was working yesterday doesn't rule out a battery problem.

Check the battery voltage with the key turned to start, if that seems ok (above 10 volts approximately) then let me know the details for the car and I'll get you the starter wiring diagrams - they're pretty simple and easy to follow but do vary a bit from model to model.
Simon

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Re: What's this Lexia error?

Post by Mandrake »

No rain up here, lovely and sunny :-D

It's not unusual for there to be no click at all when trying the starter on a flat battery, because if the voltage is too low to engage the starter solenoid (which is basically just a massive relay) then nothing will happen, no turn over, no click.

I'll tell you a little story about a flat battery on my V6 - I was doing injector balance testing which basically involves energising the fuel pump for a few seconds, then using an "exciter" to pulse an individual injector 50 times (over about 5 seconds) to measure fuel rail pressure drop. After testing all the injectors the engine has to be started and run for a few seconds before repeating the test to clear out any fuel to avoid filling the cylinder up with fuel and hydro-locking the engine. (read: bent con-rods)

Well I was having a bit of trouble with my exciter not working properly at first and also my fuel pressure gauge not giving consistent results, so the test was repeated a number of times over about an hour. The fuel pump uses about 8 amps, the injectors a couple of amps, but the real killer is the frequent engine starts with no period of running afterwards to replenish the charge lost during the start.

The engine was starting perfectly with barely any sign of turning over slower than usual - right up until it completely failed to start, only 10 minutes after the last time it started ok. No movement of the starter, not even a click from the starter solenoid, just silence like you're getting. Surely the battery couldn't have dropped so much in that 10 minute period with only a few amps being drawn for the injector testing ?

Apparently so, because the battery was flat and was dropping to less than 8 volts with the key in start which is insufficient to activate the starter solenoid. (10.5v is normal at the starter solenoid after voltage drops are taken into consideration)

I charged the battery up over night (I only have a trickle charger) put it back in the next day and it was fine. The car has never failed to start since so its not a faulty battery, it was just discharged.

It just goes to show how quickly you can go from starting to a no start condition when the battery is discharged. With a faulty battery that's not holding a good charge it can happen even more abruptly.
Simon

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Re: What's this Lexia error?

Post by DHallworth »

Turning the key and nothing happening was exactly the same fault that the C5 I bought had.

To check it if you get a couple of lengths of wire with a crocodile clip on each end for ease and attach one of them to the positive on the solenoid on the starter motor and the other to the negative on the starter then put them onto a headlight bulb if the wiring on the car is ok you will see the headlight bulb illuminate when you turn the key to the start position.

This will rule out any wiring/immobiliser faults on the car and will tell you straight away if the starter is knackered as if the car is giving power to the starter (illuminating the bulb) then the wiring etc is ok, if the bulb doesn't light then you know you have a fault somewhere other then the starter.

In my case the C5 starter didn't even try to click or anything, I checked the above and when the bulb lit I swapped the starter for another one which is running perfectly now.

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Re: What's this Lexia error?

Post by Mandrake »

Unfortunately I don't have the exact wiring diagram for your car as Sedre doesn't cover the Series 1 Xantia :( However what I've done is entered RPO 7750 which is a January '98 Series 2 Xantia and chosen the Turbo Engine, I think this will be very close if not identical. Here are the diagrams:

https://dl.dropboxusercontent.com/u/782 ... nciple.pdf" onclick="window.open(this.href);return false;
https://dl.dropboxusercontent.com/u/782 ... lation.pdf" onclick="window.open(this.href);return false;
https://dl.dropboxusercontent.com/u/782 ... Wiring.pdf" onclick="window.open(this.href);return false;

The circuit is very simple, the high current connection to the starter goes directly from the battery to the starter, the supply for the starter solenoid goes through BMF 1 fuse A, which is the right hand maxi fuse in the top row of four in the engine bay fuse box (see the installation pdf above) from there it goes through the ignition switch and then to the starter solenoid terminal on the starter.

Not much to go wrong there! No relays involved like there is on an automatic.

The same maxi fuse supplies many other things via the ignition switch so if it was blown then various other things wouldn't be working either.

My money is on either a flat battery or a fault with the starter. Measuring the battery voltage when trying to crank and then measuring the voltage on the starter solenoid terminal on the starter when trying to crank should tell you what you need to know.
Simon

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Re: What's this Lexia error?

Post by Mandrake »

If the figure is indicating the percentage that the waste gate is open (and I don't know if it is) then it could be normal for it to be at 0% when the engine is not under load as the turbo won't be producing more than its maximum boost. Just revving the engine up while stationary won't put it under significant load so won't generate much boost pressure. (What does the MAP reading go up to when you rev the engine ?)

A waste gate starts to open when maximum boost is exceeded to regulate the boost to that maximum figure. On an older turbo the waste gate opening pressure is the same for all engine RPM and is mechanically regulated with a simple diaphragm - the pressure in the manifold operates a dash pot that pushes a lever that opens the waste gate vane...

On the TCT engine not only is the waste gate operated by ECU, but the maximum boost pressure varies with engine RPM - it has its own mapping table for boost with maximum boost available at lower RPM and reduced boost available at higher RPM.

The only way to test it would be to put the engine under load - accelerate hard up a hill and see if the waste gate OCR % increases above zero, and at what MAP reading it does so. Ideally you'd want a co-driver to do that safely! :)
Simon

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Re: What's this Lexia error?

Post by Mandrake »

What does it say for Idle OCR ? This is the idle control valve. Normally it should be between 30-40% at idle with no A/C running.

Does it idle smoothly if you just hold the throttle open slightly ?

Does the throttle position percentage read correctly on the Lexia through the full opening range of the throttle ? (this can be checked with the engine stopped but key on)
Simon

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Re: What's this Lexia error?

Post by Hell Razor5543 »

I wonder if the first pic in this post would help?;

http://www.frenchcarforum.co.uk/forum/v ... =3&t=42858" onclick="window.open(this.href);return false;
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Post by addo »

Look straight through the "Hutch" in Hutchinson with your X-ray vision.
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