Lexia, and Xantia auto boxes

addo · Post by **addo** » 08 Mar 2009, 10:04

A query for the Lexia-rich, from a Lexia-poor person.

What parameters can be read from the trans, both static and in service?

What codes are able to be logged in the trans ECU? Do they self-purge over time, if no recurrence?

Thanks, Adam.

Post by **CitroJim** » 08 Mar 2009, 10:38

I can only speak for the 4HP20 and only briefly at that but the Lexia tells quite a lot: It lists a good few paramaters and the currently selected program along with what gear is selected and so on. It also reports the state of external sensors such as the brake switch.

I'm sure the AL4 will be much the same as it too is an auto-adaptive 'box very similar, both in operation and construction to the 4HP20 but smaller. One major difference is that it uses brake bands rather than clutch packs.

Faults, as far as I know, are permanant until reset.

One very important thing on the AL4 is the "Wear Indicator". This is a counter that increments over time to tell you,via flasing snow and sport lights, that your oil needs changing. Only a Lexia can reset it I believe. The 4HP20 does not have such a contrivance. It lets you know it's worn by whining and then dying

EDIT: When the AL4 Wear Indicator triggers, the 'box will only select reverse and third gear "emergency". It drops into limp-home mode until reset

The earlier 4HP14 and 18 are both fully hydro-mechanical and have no ECU to worry about.

addo · Post by **addo** » 08 Mar 2009, 10:51

Hi Jim, what I'm still chewing on is the secondary (BVA only) TPS.

I strongly suspect this has a faulty or worn track, but wondering what risks may be entailed if I disconnect the plug and test drive it. That would leave shift points as a function of internal pressures/speeds, the kickdown and VSS.

I don't want to do it if this will put the trans into limp-home mode and log a fault that needs Lexiating post-haste.

Regards, Adam.

Post by **CitroJim** » 08 Mar 2009, 11:28

addo wrote: I don't want to do it if this will put the trans into limp-home mode and log a fault that needs Lexiating post-haste.

That's a tricky one Adam. The risk is a bit high that it will unless proven otherwise... I'd not risk it as I guess Lexiae are not that common down your way and it's a bit of a hike to bring mine over to you

I'm all a bit unsighted on this issue. What's the symptoms you're having?

On the V6/4HP20, the butterfly position is used to work out when the 'box kicks down. I would assume that's the primary function of the secondary TPS on yours. It may not be a pot at all but a set of switch contacts to signal closed (i.e idle), mid-throttle and WOT to the gearbox ECU...

Give me the exact model and year and I'll dig the wiring diagrams out for you and discharge my duties as requested in your last PM

hirsty · Post by **hirsty** » 08 Mar 2009, 12:42

With regard to the AL4 box and oil changing, my box has done 144k miles without an oil change. Aren't the UK boxes supposed to be sealed for "life"? Apart from the occasional snatch when caught between changing down to 1st from 2nd, my box seems reasonably smooth.

Keith

Post by **myglaren** » 08 Mar 2009, 13:15

Is it possible that it depends on how those miles have been clocked up? Long motorway journeys are likely to place a much lower level of stress and wear than lots of urban driving, as with most other mechanical compnents, not least the engine.

Apologies for stating the bloody obvious

Post by **CitroJim** » 08 Mar 2009, 14:05

This is how the "old oil" warning works on the AL4

Using the parameters of automatic transmission oil temperature and the time for which the oil is subject to a high temperature, the ECU increments an "old oil" counter. When this reaches the calibrated maximum valve, the ECU orders the "Sport" and "Snow" warning lights to flash on the control panel to warn the driver that the automatic transmission oil needs changing.

So yes Steve, absolutely, motorway miles will be kind to it and the warning will take longer to appear than one that's regularly thrashed or used for towing.

hirsty wrote:Aren't the UK boxes supposed to be sealed for "life"?

A better description might be "lubricated for life" Keith. It is possible to drain the oil and top it up. The problem is that only about half will drain as the other half is trapped in the torque convertor.

It's a good idea to three partial changes in rapid succession and then, at least a good percentage of the oil will be new.

I have a PDF Training Manual for the AL4. It's big (1.2Mb) but if anyone wants a copy, I should be able to send it via email.

Although I origiaally downloaded it from somewhere, I can no longer find the site

addo · Post by **addo** » 08 Mar 2009, 22:13

Jim - there are two conditions under which operation is poor.

If the pedal is suddenly depressed to WOT, kickdown is a "maybe" event. Not a certainty.

Also (and more common given my driving) cruising in third gear around 25MPH under an extremely light throttle with featherweight increase (eg, a mildly steepening incline) it suddenly "lurches" from third to second.

I would assume kickdown is both determined by the "excition switch" next to the doseur and secondary TPS. If it's getting no signal from one but an indication from the other - perhaps it is waiting for VSS output to drop markedly, confirming a "need for speed".

Also, the light throttle lurch is really suggestive of a poor quality signal to the trans ECU; again an inability to accurately determine WTH is going on with the car's progress.

There's an ELIT available about ten miles away; free by arrangement if I can operate it (never tried). Lexia, however, is a $66 minimum fee at the dealers and only by prior appointment.

Oh, and it does whine slightly but I assumed it was a mismatched final drive pair courtesy of the rebuilders. Reading the 4HP20 thread, I'm now not so sure! It would be nice if someone could reference the dominant frequency of this failure mode.

Regards, Adam.

p.s. Jim: February '99 build, AL4 replaced 25000 kilometres ago with rebuilt at a dealership. Mechanicking of the swap appears to have been somewhat amateur.

DickieG · Post by **DickieG** » 08 Mar 2009, 22:22

addo wrote:There's an ELIT available about ten miles away; free by arrangement if I can operate it (never tried). Lexia, however, is a $66 minimum fee at the dealers and only by prior appointment.

If the ELIT is up to date it will do pretty much all that a Lexia will do, operating an ELIT is pretty much self explanatory and fool proof if you're worried about cocking up the ECU/gearbox.

addo · Post by **addo** » 08 Mar 2009, 22:24

Thanks DG - any suggestions on how I may check if it's fully up-to-date?

Regards, Adam.

DickieG · Post by **DickieG** » 08 Mar 2009, 22:43

addo wrote:Thanks DG - any suggestions on how I may check if it's fully up-to-date?

On an ELIT there are two types of memory card, the early ones (up to around 97 I think) couldn't be updated whereas the later version could via CD. IIRC a search on aussiefrogs should find a link complete with pictures to identify which is which.

I'm pretty sure that if the ELIT isn't up to date with the ECU it simply won't read it. The only thing you may be missing out on is a software update (of which there have been a few for the autoboxes).