A4 B7 CVT intermittent starting issue

[Ianswebb]

Hello everyone,

I have an issue I hope you can help with.. As the title states I have an intermittent starting issue with my 2007 A4 CVT. Seemingly, without rhyme or reason when turning the key, all the dash lights come on as expected but when I go one step further and try to start the car there is nothing, no dimming of lights, no starter solenoid clicking, nothing!  Yet I'll try another time and it will start bang on cue.

The battery is good and the grounds are good. I'm getting voltage to the starter motor, although I am yet to test the switch wire. I don't have any fault codes as yet, namely because i'm only running VCDS lite 😬 and can't access all the modules.

There is one thing I've noticed when it is playing up.. When all the dash lights are on, the 'Automatic Selector Lever Lock' (between P and R) light does not come on and the selector can be moved without pressing the brake pedal, ordinarily light would be on and pressing the brake pedal releases the lock.  

This points me in the direction of the brake light switch, although the brake lights appear to work fine.

Anyone got any advances on this theory?

Ian    

[Magnet]

Hello Ian,

I too would go with your theory, and couple it with checking the Park switch -as starting points (pardon the pun).

Kind regards, 

Gareth. 

[Ianswebb]

Hi Gareth,

All puns gratefully received. Laugh of you cry, right!?.. and thanks for mucking in! I'll give TPS a shout tomorrow.

The brake switch I've just taken out is a genuine part although I'm going to hazard a guess and say its not a factory original. It doesn't seem dusty enough to me, although there some slight rubbing marks on top, so who knows 🤔. None the less for that I think I'll go for the same again. 

Regarding the Park Switch.. is that the same as a neutral safety switch? (Apologies if that is a really daft question, I'm new to the world of automatic gearboxes). To date, I haven't had any key release issues.

Ian

[Ianswebb]

Got a bit of an update..

First off TPS don't sell to regular members of the public! I'm sure I walked in to one of their branches years ago and bought some stuff, but perhaps I didn't. Oh well!.. Got a new brake light switch from the dealer, and was pleasantly surprised that it only cost £17. Unfortunately, it didn't work.

I have however unearthed a fault code from the 'Instruments' module...

01315 - Transmission Control Module

004 - No signal/Communication  

The control module part number is 8E0 920 982 N

Would anyone happen to know where this bad boys is located? I'd like to make sure all the connections are clean from there back to the TCM so I can start ruling everything out, in a vain attempt to avoid sliding down the slippery slope that is TCM repair/replacement (dealer quoted £1327inc vat(part only) and said that it would need coding aswell 🤮).

 

Ian

[Ianswebb]

May well have found my issue.. Way dodgy connection on fuse 31! Specifically the right connector. Not too sure how easy that is going to be to replace.. I'm going to hazard a guess and say it's gonna be a ball ache 😠.

None the less for that, I've wedged the fuse in for now so there is good contact, while I decide how best to tackle it.

Ian