Audi A6 S Line 2005 Multiple faults maybe or electrical fault?

[mippy]

Dear All,

First of all Happy New Year and I hope someone can help me.

I will try to get to the issue, without getting too distracted.

Purchase this 2005 A6 S Line Saloon 2ltr Diesel, not long ago, with an ABS fault. ABS unit has been repaired and refitted into vehicle, along with a new battery as previous one wouldn't hold charge.
(not sure if this is relevant, when acquired vehicle had been stationary for approx 2 months and had to trickle charge to start up etc to take to repair location.) Prev owner said ABS was faulty, when driving to my place, it has ABS light on, handbrake light, ESP light and ESP button would have no effect.

ABS unit back on, friend with small handheld device, removed the fault code 01435 Brake Pressure Sender G210.
Vehicle drove fine straight after! yay! (Christmas Eve)

then approx 50-60 miles later cannot remember if restarted the engine or not... the fault lights all came back on... ESP, HandBrake Light, ABS light with the message to tell me to drive it to nearest garage etc... parking sensors are also intermittently working, which i thought was strange. but brakes error flashing permanently on dash display

been using the car anyways as the car works and the brakes work!!

yesterday (new years day) returning home, still driving with all the lights on and it beeping at me when pulling away, put car in reverse, parking sensors kicked in and is working fine!!?? strange... and has done since!?? ABs and brakes lights gone, as have my dash display back.... displaying temp and mileage left with fuel etc...
Today went shopping still no lights nor any errors!
parked went shopping and loaded shopping in car, now the boot light is on, even though the boot is definitely shut!?? yes definitely! and all ABS, ESP, Handbrake fault lights all back on!
driving home, boot is open.... grrr.... shut boot, boot light still on at dash.
and all abs, esp and handbrake fault lights are all back on again...

someone have any ideas....?

i mentioned the battery as some are saying make sure the battery is correct due to the vehicle being so electronically dependent if so does anyone know whats this battery should be

is it a wiring fault as so many things cannot be wrong with it??

Many thanks in anticipation

[dan2485]

The battery is probably goosed.

There are a lot of posts regarding this type of fault, the ABS is normally the first thing to flag up when the battery voltage drops.

[MarkTM]

Sounds like battery, alternator or both IMO

Had similar faults on mine last year and it was a faulty alternator.

Did you not check/record the spec of your original battery prior to replacement?

Any battery place should be able to test both with a multimeter.

[mippy]

Many thanks for your reply, unfortunately, the previous battery was not secured in, and therefore unsure of its own compatibility with the vehicle. When new battery was purchased, it was aligned with registration and spec of vehicle, so i do not know if i was supposed to purchase a specific battery.

Also does anyone know of the importance of 'coding' the battery in?

Thanks again

[MarkTM]

Battery coding only necessary if a different spec installed from the original, as you don't seem to know what the spec of the original is, then it's a high probability that it does need coding.

[inspectorman63]

Electrical strangeness while running points to the alternator, IMO. Coding not hugely important; the system will learn, over time, the change in charging characteristics caused by swapping batteries. But there are situations - like your car having stood for 2 months and the battery being very flat - where the magic box decides, erring on the side of caution, that it had better treat the new battery as if it were the old one. In these circumstances I would recode the entry with VCDS. So charge the battery, check alternator output and recode the battery entry.

[mippy]

Would just the battery really cause this many issues? Another head scratcher is a couple of days ago the key symbol with battery came up on dash display but has not reappeared again since......

But the boot lid is a puzzler as it still displays the boot being open and it certainly is not but it opens whilst driving too!?

Thanks for any help

[dan2485]

The low voltage conditions cause the various modules to generate spurious messages.

As for the boot this could just be the switch not being made, Possibly a just a random error.

[dan2485]

Did you buy the car from a trader if less than 6 months ago then return the car and get them to fix it.

It is not uncommon for traders to swap out batteries to get another car going then put back any old battery.

I would also check with the ABS unit repair as to what they did as if this is a battery issue then they would have not done much.

[MarkTM]

ABS/ESP/EPB fault on mine was due to a dodgy wiring harness to my drivers side front wheel, replaced with a new one from Audi (£79 inc) and all was back to normal....check the state of the wiring and if there are any obvious previous repairs (insulating tape being a giveaway).

As you'll know it's an MOT fail.

VCDS scan will tell you which side and you can then swap the ABS sensor for the good side to eliminate that, if the fault then switches to t'other side you'll know it's the sensor. If you have access to a set of ramps a 10 min job and a circa £27 fix. If not that it could be the wheel hub sensor ring...but am guessing with all 3 faults it will be the harness

Boot opening when driving must be scary...can only think a faulty catch?