AL4 transmission in emergency mode

[Mr Micawber]

Hello Everyone, I am new to this forum and this is my first posting. It's a plea for assistance I'm afraid.

We have a 2003 C3 1.4 (petrol) with the AL4 automatic transmission. It has two mysterious faults; one is that the VAN network positive supply is randomly being switched on and off by a relay in the BSI when the car is not being used. I have been energetically pursuing this problem for some time and I've concluded that the BSI itself is responsible (because the relay continues to operate with all connections removed except battery +ve and -ve). Before delving into further complexity I carried out one of the so-called 'resetting' procedures involving an innocuous sequence of routine operations:

BSI Reset / Battery Disconnect / Reconnect Procedure

It may be a cruel coincidence but the next time I started the car the 'sport' and 'snow' instrument pod warning lights flashed in unison, the gear selection indicator showed a horizontal line and the transmission selected only 3rd. gear and reverse. I took the car on a short test drive with no improvement, and when I came to restart the engine I found that the selector was locked in 'park' and the 'check engine' light was now illuminated too. I released the selector and limped home, in 3rd. gear only, and commenced internet research which was how I discovered this forum.

Yesterday I removed, dismantled, cleaned and lubricated the selector switch on top of the transmission but the fault remained. I have read that the ATF 'oil counter' can trigger the flashing 'sport' & 'snow' lights, but surely it wouldn't place the transmission in emergency mode would it?

There is a nice, family run garage business very close by, and they have offered to connect their generic diagnostic equipment but admit that it may not be helpful. Such devices don't give me confidence either, and I don't want to use a main dealer. There's an independent with a Lexia, but they are ten miles away and I don't like driving the C3 too far in this state as I've already noticed the smell of hot brake band linings. I think the nearest forum member with a Lexia is also a fair distance away, but this would be my favourite option by far if practical.

Sorry to have such a tale of woe on my first posting. We're anxious to get the C3 repaired because it's the only vehicle we have which is big enough to transport my wife's power wheelchair.

All suggestions gratefully received. I am technically competent (but not too hot with computers) so am willing to try anything.

Simon.

[myglaren]

Welcome Simon.

While I can't advise of any action other than to perform a Lexia diagnostic, I am a little suspect of the BBA Reman advisory on the resetting procedure - mainly as it differs from the one I learned.

BSI Reset / Battery Disconnect / Reconnect Procedure
My advice was to try and do this procedure overnight and to remove and charge the battery to ensure that the system had full voltage on reconnection. A failing battery can produce the symptoms that you are experiencing - the ECUs are very susceptible to low battery voltage and can produce any amount of strange error reports.

[Mr Micawber]

Many thanks for the welcome Myglaren, and for your corrections to the BBA Reman resetting procedure. I'll try this and report back.

Simon.

O.K., I've followed your instructions but I'm afraid it has made no difference to either the BSI fault or the transmission fault.

Can anyone help me with a Lexia session please? I need to know why the gearbox is in the emergency mode. Many thanks.

Simon.

[danielsydney]

Simon wont a dealer in the UK have the lexia machine that can tell you whats wrong?

[myglaren]

Simon wont a dealer in the UK have the lexia machine that can tell you whats wrong?

Simon,
Have you seen the list and map of our Lexia owners who will run diagnostics for other members?

If not, it is here

[CitroJim]

To properly diagnose a fault such as this it is essential to have a session on a Lexia. The reasons for an AL4 throwing up the sport and snow lights and failing to 3rd emergency are vast and impossible to guess at.

Make sure whoever you take it to for the diagnostic is knowledgeable of auto-adaptive gearboxes as the fault(s) the Lexia may uncover are not intuitive and need knowledge to understand and interpret...

I hate to think how the gearbox 'talks' to the BSI and I'm wondering iof the gearbox going ito limp is a red herring caused by ungappiness in the BSI, particularly as it happened after youb tried resetting it. It may have lost knowledge of even having an automatic gearbox installed...

All the more reason to get a wise person armed with a Lexia to have a look - it could save weeks of poke and hope...

[Mr Micawber]

Thanks for your help everyone.

Daniel; yes, UK main dealers have Lexia but also take a rather holistic approach to problems like this. I'm also a very "hands on" car owner when it comes to maintenance, and many main dealers here are uncomfortable with that.

Steve (hope I've got the name right in view of your Avatar); many thanks for the list. I would indeed like to hear the advice of a forum member experienced with Lexia so will send some PMs.

Jim; thanks for your thoughts which are appreciated. Regarding the BSI, the technical information I've studied shows that it's strictly a 'Body control unit'. The engine and automatic gearbox have their own ECUs, but I agree that with multiplex electrical systems anything is possible!

I will report back with developments. We need to get this car back on the road a.s.a.p.

Best wishes,

Simon.

[Chris570]

just to add to this Simon,

as far as i'm aware with multiplexing yes you are right each part does have it's own ecu BUT it needs a Master ECU as it is the only one that sends info out to the individual ECU's so if the Master ECU (read BSI unit) is faulty or has a duff config it can and will cause all manner of problems. If you know computer networking its a very similar principle to MAC Addresses and a hubbed not switched network.

[Mr Micawber]

Thanks for that Chris. I'm hopefully in the process of getting a Lexia session organised so all should be revealed!

If you know computer networking its a very similar principle to MAC Addresses and a hubbed not switched network.

All gobbledegook to me I'm afraid.

Simon.

[Mr Micawber]

Well thanks to AndyJ76 my car has now had a Lexia session. There were communication faults reported with the automatic transmission ECU and the ABS. The wiring diagram shows that the CAN bus goes to the ABS ECU first then, via separate pins, continues to the AT ECU. So I'll see what I can find out from those clues. Any advice on these data networks will be gratefully received though!

Simon.

[CitroJim]

That's bizarre A bit like connecting the telly via the kettle but then I guess there's a bit of logic here in that the telly could put the kettle on when the adverts come on...

However, I guess the logic is that if the ABS flies into action then it can manipulate the autobox to effect a safe stop or regain control...

It's very likely you'll find you have an ABS fault rather than a comms or gearbox fault. I believe there is a condition that can happen to a BMW where a duff ABS sensor is indicated by a raft of autobox faults...

The trouble with there multiplex networks is they can get their electronic knickers in such a twist that diagnostics are not conclusive so on that basis I'd be checking your ABS sensors for a start...

Bizarre but there you go...

[Chris570]

It's more like a token ring network Jim, saves wiring

[CitroJim]

It's more like a token ring network Jim, saves wiring

I'd rather have lots of wires and no network Chris, Token Ring or otherwise... I'm quite happy to leave networks where they belong - at work - they have no place in a car

[Mr Micawber]

It's more like a token ring network Jim, saves wiring

Hello Jim & Chris,

Yes, I'm learning bits and bobs as I go. As I understand it the CAN bus is rather like a ring main in a house. The clever bit is that each message sent on it can be targeted at a particular ECU.

The original idea was that this system would save wiring as Chris says. However, the potential flexibility of one ECU communicating with many others has actually resulted in a far more complex (and impenetrable) wiring loom than with the conventional electrical circuits we had before!

Simon.

[Chris570]

lets be fair to it though, for 99.9% of cases it works well and means you can cut down on the amount of sensors required as with a common data ring info can be shared between all the ecu's with just a few wires as opposed to the rats nest you'd need to interconnect each ecu individually, not to even mention the additional config of each individual ecu depending on car spec (So each ECU would know to talk to each other one). At least with the BSI you can just config that and off you go.

That said i do like my non-multiplexed cars. But as soon as i get that wire fail on the xantias front crossmember loom i might have to revise my position.

Swings and roundabouts really.

(Sorry about the off-topicness but the FCF has a minimum quote of thread de-railments to meet)