A6 C7 not starting

[John Sheridan]

Hi all, first time posting. My 2015 A6C7 wouldnt start(start stop not working, Visit workshop) and through up loads of faults mostly including clutch switch, Clutch posistion sensor, and a few on modules not working. 

Car starts on a bump start but not on a jump start. Cleared faults but still no start. Battery is above recommended %. Replaced clutch switch which is connected to master cylinder so £200 and still not starting. Still saying electric module intermittent. 

Any ideas of where the problem is? We were thinking electrical failure in cable to starter. Run a wire direct to starter and it starts no problem. 

Ive had damaged wires on this side of the car before. Had multiple warning lights on dash and was in fact corroded wire in loom to ABS sensor. 4 different cracks in wiring. 

Any idea would be appreciated. 

 

Thanks

 

John

[John Sheridan]

Hi all, first time posting. My 2015 A6C7 wouldnt start(start stop not working, Visit workshop) and through up loads of faults mostly including clutch switch, Clutch posistion sensor, and a few on modules not working. 

Car starts on a bump start but not on a jump start. Cleared faults but still no start. Battery is above recommended %. Replaced clutch switch which is connected to master cylinder so £200 and still not starting. Still saying electric module intermittent. 

Any ideas of where the problem is? We were thinking electrical failure in cable to starter. Run a wire direct to starter and it starts no problem. 

Ive had damaged wires on this side of the car before. Had multiple warning lights on dash and was in fact corroded wire in loom to ABS sensor. 4 different cracks in wiring. 

Any idea would be appreciated. 

 

Thanks

 

John

[Stevey Y]

Hi it could be a damaged wire on the plug for the clutch position sensor, somewhere on here is an old post for an A4 which runs the same system the guy ended up Buying an IDOS system [expensive] but it does electrical test and trace in the wiring loom, other than that I can only suggest a good auto electrician, all this is based on your wiring bypass of the clutch position sensor.

Steve.

[John Sheridan]

Thanks Stevey,

I had an auto spark fix my older problems with the multiple faults around the off side ABS/wheelspeed sensor which he found to be 5 breaks in the actual loom along the firewall/bulk head up around the DPF etc. Im wondering is this same issue with the wiring from starter up in same direction. 

Thanks

 

John

[Stevey Y]

21 hours ago, John Sheridan said:

Thanks Stevey,

I had an auto spark fix my older problems with the multiple faults around the off side ABS/wheelspeed sensor which he found to be 5 breaks in the actual loom along the firewall/bulk head up around the DPF etc. Im wondering is this same issue with the wiring from starter up in same direction. 

Thanks

 

John

Hi if you have a good auto spark that would seem to be the way to go, given the option of buying an expensive bit of kit which you may only use once versus a few hours of his time its a no brainer, otherwise you will spend hours howling at the moon before you find the fault if you actually ever do, I have normally been ok with electrical faults but this brand of vehicle gives me the willies as the electrics are beyond complex. Its more than possible the loom up from the clutch position sensor is broken, from memory the guy  I was talking about ended running a bypass spur on the existing loom to fix the problem.

Steve.

[John Sheridan]

1 hour ago, Stevey Y said:

Hi if you have a good auto spark that would seem to be the way to go, given the option of buying an expensive bit of kit which you may only use once versus a few hours of his time its a no brainer, otherwise you will spend hours howling at the moon before you find the fault if you actually ever do, I have normally been ok with electrical faults but this brand of vehicle gives me the willies as the electrics are beyond complex. Its more than possible the loom up from the clutch position sensor is broken, from memory the guy  I was talking about ended running a bypass spur on the existing loom to fix the problem.

Steve.

Thanks mate. Yeah, we were at it all day today. Had the full wiring loom cut open but couldnt find the problem. We ran a wire across the starter wiring and bypassed it for now. Car still starts on a button for now but still flags up the "stop start fault". The auto spark is off till after new year so had to do something to get it mobile again. Car was previously a taxi so the harness has been hacked in places. Im guessing broken wire in harness as you stated may be my issue as its in same area that my last multiple fault issue was and it was a loom broken in 4 different places. 

Thanks for the help. 

John

[Stevey Y]

On 12/28/2024 at 8:18 PM, John Sheridan said:

Thanks mate. Yeah, we were at it all day today. Had the full wiring loom cut open but couldnt find the problem. We ran a wire across the starter wiring and bypassed it for now. Car still starts on a button for now but still flags up the "stop start fault". The auto spark is off till after new year so had to do something to get it mobile again. Car was previously a taxi so the harness has been hacked in places. Im guessing broken wire in harness as you stated may be my issue as its in same area that my last multiple fault issue was and it was a loom broken in 4 different places. 

Thanks for the help. 

John

Hi the stop start fault may have become embedded but you can try and clear it if you have access to VCDS I have suffered that before when I have replaced parts, these cars are obsessive with hanging on to old faults I used to get the stop start fault randomly towards the end of my cars life and the hysterical thing is that I used it as a taxi but never buggered about with the wiring, my theory is that from 2010 on they have been cutting back on the quality of the parts as I ran one of my Mondeos up to 360k and never had a days trouble with the main looms only the headlight plugs corroding which was a very common fault.

Steve.

[John Sheridan]

16 hours ago, Stevey Y said:

Hi the stop start fault may have become embedded but you can try and clear it if you have access to VCDS I have suffered that before when I have replaced parts, these cars are obsessive with hanging on to old faults I used to get the stop start fault randomly towards the end of my cars life and the hysterical thing is that I used it as a taxi but never buggered about with the wiring, my theory is that from 2010 on they have been cutting back on the quality of the parts as I ran one of my Mondeos up to 360k and never had a days trouble with the main looms only the headlight plugs corroding which was a very common fault.

Steve.

Thanks again Steve,

 

Yeah im gonna have a guy look at it who has a VCDS system and try to clear all tge faults. My OBD11 is good but keeps all historical faults too. 

Looms becoming brittle seems an ongoing issue on the A6C7s especially the Ultras. 

I will post on here every step because if I can help others and save them some money then thats how these forums are supposed to work. 

Thanks mate  

John

[cliffcoggin]

2 hours ago, John Sheridan said:

I will post on here every step because if I can help others and save them some money then thats how these forums are supposed to work. 

Good man. I wish others were as obliging as you.

[DaveOL89]

Just a quick one, don’t know if you’ve solved this, but is the boot bone dry around the battery or damp or soaking?

 

water often gets in there and could be something as simple as a bad earth from the water 

[John Sheridan]

On 1/2/2025 at 8:01 PM, DaveOL89 said:

Just a quick one, don’t know if you’ve solved this, but is the boot bone dry around the battery or damp or soaking?

 

water often gets in there and could be something as simple as a bad earth from the water 

Hi, I checked the boot and there was a small small bit of what looked like damp or oil under the metal bracket which holds the module, under the battery etc. We ruled out any affect that this would have had as it wasnt in contact with anything and the plugs were all dry. 

I have installed a push button for now to bypass where the fault is until I get an auto spark and get paid again as finding faults in Audi's are expensive. 

One question I have for people reading this thread is, do new clutch master cylinders (with clutch switch) need coded to the car? If they do then I could save myself a full auto spark investigation. I replaced mine with a genuine 1 from TPS but didnt code it. 

I will keep this thread updated. 

Thanks

John

[Stevey Y]

54 minutes ago, John Sheridan said:

Hi, I checked the boot and there was a small small bit of what looked like damp or oil under the metal bracket which holds the module, under the battery etc. We ruled out any affect that this would have had as it wasnt in contact with anything and the plugs were all dry. 

I have installed a push button for now to bypass where the fault is until I get an auto spark and get paid again as finding faults in Audi's are expensive. 

One question I have for people reading this thread is, do new clutch master cylinders (with clutch switch) need coded to the car? If they do then I could save myself a full auto spark investigation. I replaced mine with a genuine 1 from TPS but didnt code it. 

I will keep this thread updated. 

Thanks

John

Hi the master cylinder and position sensor are plug in and play so no coding, I honestly would be looking for a wiring fault as the position sensor is what's known as a slave sensor its simply not giving the correct trigger pulse because there is a break in the link somewhere, you have proved that by getting the bypass to work, as for the fault finding being expensive just about anything on these cars is expensive, you are only left with finding a cheaper way of fixing them, believe me when I tell you I fixed most of the problems on mine but there is no cheap just cheaper, I have family in the states and one of them bought an RS6, the reason he got shot of it was every time he went to the dealers for a small fault it was a minimum of $1200, the Dodge Challenger he now owns has been more reliable as an older car and as he puts it just about everyone and their dawg knows how to fix em, for less $$$$$.

Steve.