faulty computer display

[anotherjo]

Hi. I'm a newbie with an 05 TDi estate purchased 4 months ago. The computer display inexplicably went faulty last week. The "door open" icon came on when I got into the car and showed when the door was closed (car icon with all doors closed). However, when I switched the ignition on, this car icon remained, instead of the "normal" multifunction display. As soon as I touch the the MFD switch everything reverts to normal as long as I'm driving the car. When I switch off at the end of my journey, the little car icon comes on again. The indicators no longer flash once when I'm locking the car and the little car icon stays on (I'm not sure for how long because by the time I get back to the car it is off, only for the whole story to repeat itself). Any suggestions?

[cruiser647]

Hello!

Presume you've checked all doors, boot and bonnet openings? Might be worth opening them all and then closing them all again?

Filler cap too?

[TIDYDUBS]

Hello........Are you referring to a 3B Passat estate the older shape or the new shape 3C? When did you first notice this? Weather conditions????

[anotherjo]

Hi again. Thanks for the responses.

Yes, I have tried opening and closing all the doors, bonnet, boot and filler cap, but to no avail.

I think this model is called the B5 - 2005 plates, 1.9 TDi SE estate. I wondered whether weather might be responsible as it started shortly after I had to start scraping ice off the windscreen in the mornings last week. The car seemed to mist up quite a lot inside as well, so I wondered whether there was perhaps an earth that was affected by moistness. However, despite having warmer weather this week, the problem persists. This morning for the first time, I noticed that the correct MFD showed up briefly when I swtiched the lights on, the temperature at the bottom of the display and a little "freeze" icon flashing two or three times, but then it reverted to the car icon display that was showing when I got into the car.

[TIDYDUBS]

Hmmmmmmmm i hate it.!!!! Its does my swede in.Id get a VAG COM done first see whats happening....possibly a DASH INSERT not uncommon.Id deal with the issue of the condensation issue first even tho it is winter make sure nothing wet inside like a brolly or shoes, wetsuit,wet clothing etc etc.

Thanks for the info though and it kinda points me in the general direction of a potential water leak into the foot well areas. Behind passenger side front seat first,then when that puppy is full up it will fill the front one and your Convenience ECU.

If it has not ruined the wiring connectors on the passenger side B pillar first...which could indicate why the MFD is lighting up with bonnet open i have had similar issues as you described.

The CAN bus system has not got a clue what its doing or any of the associated wiring and components.Id get a VAG COM first see whats happening. Id seriously try and access the under carpets and soundproofing to see if you have water ingress which indicates a pollen filter housing issue.......See my thread on PLENUM CHAMBER BUNGS worth a read+++

This should help bearing in mind any corrosion to wires, connectors or control units need to be done now and not left to fester away! Cause the problem only gets worse and you could result in losing your engine.............yes it can happen these bungs are a pain.

[anotherjo]

Hi Tidydubs. Thanks very much for your detailed response. I'll have to try unpacking everything you said with the car in front of me as I'm not sure if I follow all your advice. You use some abbreviations that I have no idea what they are (CAN bus?).

I'm not aware of any wetness in the car but I'll certainly have a look under seats and feel for any wet carpets etc. Your PLENUM CHAMBER BUNGS idea sounds worth following up, but once again I'll have to read your write-up fairly carefully with the car in front of me.

I'll also have a general root around for corroded wiring connectors which, if I understand correctly are routed from the engine bay via the passenger side B pillar into the car's ECU (which is located in front of the front passenger seat?)

The little car icon that I have on my MFD - is that the icon that shows up when the bonnet is open? i.e. does the car think the bonnet is open and therefore doesn't switch off this icon?

Thanks again

[TIDYDUBS]

[quote=anotherjo;1519819

The little car icon that I have on my MFD - is that the icon that shows up when the bonnet is open? i.e. does the car think the bonnet is open and therefore doesn't switch off this icon?

Thanks again

BINGO!!! if its saying the bonnet is open it will have a filled pixel display of the bonnet on the MFD.

Yea i believe you have an issue with the A pillar connectors on the passenger side not the B pillar.....if my memory serves me well it will be the light blue connector that has the bonnet switch wiring or a deep red one ill check later for you. Thats why your bonnet open warning is staying on or the switch in the bonnet lock itself is screwed.

Sorry CAN bus is CONTROLLER AREA NETWORK............

[anotherjo]

Yip, the little car icon has a filled-in or coloured-in bonnet . I opened the bonnet when this car icon was displayed this morning and it didn't change. The manual has an entirely different icon for "open bonnet" so I didn't recognise what my car's icon meant. In contrast, the "door open" warning is very clear. I still need to figure out what the icon looks like when the boot is open. Anyway, hopefully my display problem is just a loose connector that didn't like the cold/wet weather recently.

Without having lifted carpets yet (job for the weekend), I can't feel any wetness int he footwells or under the seats. However, I seem to have managed to reduce the general humidity in the car by a combination of turning up the heating (to 25 instead of 20 which I preferred to keep it at before) while recirculating the air (thinking that this would evaporate the water) and then driving with the windows open for a while to get fresh dry air into the car. At least I didn't have to scrape ice off the inside of the windscreen this morning!

I'll let you know how I get on, but thanks for all the help. I think I may check the plenum chamber bungs too just in case...

[TIDYDUBS]

I'll let you know how I get on, but thanks for all the help. I think I may check the plenum chamber bungs too just in case...

Good work the wetness will be right under the carpet if your have a rather humid car.....i remove plenum chamber bungs totally and reseal pollen filter housing good luck and best regards Tidy........

[anotherjo]

Hi again. Had a root around today and discovered that the bonnet micro switch is knackered. It was hanging loose by its wire and had obviously given the previous owner some trouble based on the number of zip ties. Neighbours inform me that the alarm has also been sounding intermittently for the past week. I gather from the forum that this is related. Two questions:

1. Is there a quick way to disable the alarm till I can sort out the switch?

2. Does anyone know how or where the switch is supposed to be fixed? It's got a little silver contact at one end, but I can't see how this is supposed to connect to the latch.

Thanks for any advice.

[TIDYDUBS]

Wow that's a first.........it should be clipped in where the bonnet latches shut. That silver part should be attatched to a little black micro switch. I think you would be better off buying the whole assembly but i will try and source a diagram for you to try and refit it.Tape that contact in the closed position for now as not to pee ya neighbours off

I would not discount your humidity issue though and as a preventative measure being as you will own your Passat for a while take those bungs out.

[anotherjo]

Thanks Tidy, a diagram would be very helpful - I can't see anywhere to clip it. I guess the little black box that I have hanging around at the end of the wire is the microswitch and the silver bit is the contact that needs to be closed when the bonnet is latched. The microswitch is taped up with insulation tape, so I may have to replace it with a new assembly as you suggest. Where could I obtain this assembly for a reasonable price if I need to go down that route?

[anotherjo]

Looks like you may be right Tidydubs - it's not the bonnet switch. Had a look last night and all the tape and zip ties are there to keep the switch closed. Previous owner must have had this issue before and deliberately removed the switch from the latch and taped it up. So I'll have to turn my focus to the potential humidity issue and ECU wiring again as you suggested.

Regarding the microswitch though, I may want to refit it if it's actually functional, so a diagram or information on how and where to fix it would be much appreciated.

[TIDYDUBS]

Ill do my best for ya............Regards Tidy

[anotherjo]

Hi again. Had a look around this weekend, trying to take the panel in the passenger footwell at the bottom of the A-pillar off to investigate the connections behind it. I couldn't figure out how to remove the panel but by bending it alarmingly I managed to get peek behind it and fiddle a bit. No indication of any wetness or corrosion there. I glanced at the MFD and astonishly, the display showed the bonnet to be closed! Everything works perfectly again. So this suggests that my problem lies in a loose or corroded connection in that area.

So firstly, do you have any advice on how to remove that panel? I removed the philips screw at the bottom, but the panel seems to be attached quite firmly higher up. I thought it must be some form of clip, but it doesn't seem to want to budge. Eventually I was only able to pull back the leading edge (the edge to the front of the car) and peer behind it that way.

Secondly, I'd like to have a look under the carpets in the footwell to see if the pollen filter housing has leaked sometime in the past and whether I should be concerned about the ECU. How do I lift the carpets? If everything is okay there, I'd prefer to leave the plenum chamber investigation for some warmer weather.

Thanks for the advice and help.

[TIDYDUBS]

Hi anotherjo sorry for lack of comms........been rather busy mate. Right try as hard as you can pull the bugger right at the back as there is a clip....a dam stubborn one!!!! I would not be too fussed at putting it back at all as they all break as its a metal type one.

All those connectors may have some corrosion in them....more on how to fix later.....ill try and do photos if possible. The seats are straight forward enough,although remove at your own risk.....sorry. There are 2 13mm nuts at the front and the 2 side trims at the back should have either torx 20 screws or no2 phillips screws that are covered.Ill attach pics in a bit ok just wanted to get the ball rolling.

The latch for your bonnet pic coming also ok?????

Regards Tidy

[anotherjo]

Thanks Tidydubs. Have also been busy and had put the problem to the back of my mind as everything seemed to be ok. Unfortunately it's forced itself back to high priority when the alarm started going nuts again last night. Will have a go at removing the panel in the morning once I've managed to open the currently frozen shut door. Have a happy Christmas.

[anotherjo]

Well, managed to get the trim panel off, unfortunately breaking the clip off in the process. Can't see any corrosion there, but discovered by shoving my fingers underneath that the undercarpet insulation is indeed wet, as you suggested it probably would be Tidydubs. So proceeded to remove the passenger seat (this turned out to be fairly straightforward) but then I could not find out how to remove the trim on the door sill holding the carpet in place. Tried too hard and managed to get a crack in that too, so gave up for the time being. Hopefully fiddling with the wires will have solved the alarm problem temporarily till I can figure out how to remove the trim.