Hi All, can someone please help me to resolve a puzzle i am stuck in. Car is Audi S4 B9, starts fine, it is damaged front end- offside. wiring looms looks fine. battery was dying, changed and coded. I am seeing issues with engaging into Gears. as soon as try to engage into gears, engine cut off, any advice on it?  Thank you in advance

 

Evening, newbie here. 
If l give you a nudge in the right direction with yours maybe you can my car to start in return. 

I’ll be crying into a post about that later 😂 

Looks to me like you’ve got a serious comms issue across the Canbus system (U112100 Databus missing message)

I’d say there’s some wiring damage you can’t see..
 

Hi thanks for your reply. I have checked the wiring and don't seems to find any broken wires, the only damage wire was ambient temperature sensor and I have replaced that sensor.

The wiring damage may not be visible externally. You could have: a break in a conductor inside intact insulation, a poor contact in one of the connectors, a short circuit inside one the components, or possibly other faults I have not thought of.

It just feels electrical because of inability to communicate. Perhaps a h/s gateway module.
How is your battery? 

If that’s dying it could be strong enough to start and idle but drop out when you put the load into the engine. 
You can get a boggo multimeter for £6. Cheap way to eliminate one problem straightaway and you can do a quick continuity test on all the plug connectors too. Won’t take long.. 

Have you checked all fuses and earths as these cause missing message faults, ABS is giving a faulty module fault and voltage fault so worth unplugging it and see if that effects any other systems Incase it’s corrupting your canbus line as your power steering module is detecting a error in the voltage lines. Is it possible someone has connected a booster pack or tried to jump start it with  the wires round the wrong way

Hi Mango, thanks for your input, I have changed the battery with new battery & registration was all done. Still having issues, need to check wiring & connectors. 
 

Hi Sid, checked all fuses they are fine, relays are fine too. Someone told me it’s a faulty ground somewhere which I need to locate. 
I will try unplugging the ABS module & Check if problem eliminates.

power steering wiring is near where the damage is as I have tried to unplug it & it started showing it on dash to stop the car. 
I have connected the booster pack few times as battery was flat & needed to check few things but never connected it wrong way. How can it effect?? 
thanks for your input Sid.

Connecting the polarity round the wrong can cause internal damage to the modules, when using a booster or jumping its best to leave it connected for a few minutes before cranking just to stabilize the voltage to reduce a sudden spike thru the cars electronics, we replace quite a few modules because of the above. 

Terminal 15 on your transmission is usually a switched power fault so that may be enough to shut the engine down when trying to shift into gear as a fail safe. 

Hey Sid, thank you for your reply, so you think one of the module is faulty? 
what do you think is faulty? 
tbh I have had enough of this & can’t really figure out the fault, will check ground earth cables again today & the connections. 
what do you think I should be checking? Once again thanks for your input. Really appreciate it 

The car starts so you can rule out BCM and ecu, I would go back to basics and check gearbox module and abs for earths and live feeds first and costs nothing, without specialist equipment can lines are hard to check but a good power probe or multimeter might pick up  fluctuating frequencies which atleast indicates the wires are okay. 

Hi Sid, thanks for your reply, just to mention here, when I clear the transmission & steering errors car did get engaged in the gears twice, mostly the errors coming back straight away so it’s not even possible to clear errors, I am using Carista. 
I have the mutilmeter & car electrical tester so will check these today & will get back here. Thanks for your help.

This is worth checking

Made any progress?