audi a6 4G no start,no crank

**smokinjoe** · 26th May, 2020, 07:50 PM

hoping someone can offer some assistance with this issue, the car arrived as a non runner and new genuine clutch switch/cylinder installed, its a 2015 audi a6,I can start the car by adding 12v to starter relay but nothing from the button only clicking from relays below the steering column,I have replaced the brake boost sensor and clutch switch which has made no difference,also when the car is running the brakes don't feel right as if they are sticking with a knocking sound,I tried bleeding the brakes and still the same,Also i have tried to get information on the dtc's in the scan below but without success

Log-15 A6-WAUZZZ4G8FN057175-204349km-126976mi-non start.rar

thanks.

**rui** · 26th May, 2020, 09:31 PM

I've been seeing the errors that the car has.
you already changed the clutch pump (pedal) that has the sensor if we are pressing the pedal or not.
As for another malfunction, see if you have no damaged wires.

**smokinjoe** · 26th May, 2020, 10:27 PM

Originally Posted by rui

I've been seeing the errors that the car has.
you already changed the clutch pump (pedal) that has the sensor if we are pressing the pedal or not.
As for another malfunction, see if you have no damaged wires.

yes the clutch cylinder has been replaced and bled but no response from the start button,i'm not sure if new clutch switch must be calibrated but can't find an option to do it with vcds, I have checked the brake boost sensor at the master cylinder for power and have 5v and gnd so at this point i'm not sure whether i have wiring problems or mechanical brake problems as when I cross the starter relay and drive it the brakes don't seem right and just to add that when it is driven this way I have no warning messages displayed so it drives with no issues apart from poor brake response,is there any common places to check for wiring problems?
thanks.

**wodorof** · 26th May, 2020, 10:31 PM

on vcds you can see clutch pedal sensor value (if i am right it goes in 0-255) some of these were faulty and had maximum point way too early

**smokinjoe** · 26th May, 2020, 10:41 PM

Originally Posted by wodorof

on vcds you can see clutch pedal sensor value (if i am right it goes in 0-255) some of these were faulty and had maximum point way too early

in parking brake module the clutch position shows "unknown" and in abs it reads 15% to 85%,so there seems to be some confusion somewhere in the system as the parking brake doesn't report any faults and abs only giving errors for the brake boost sensor.

**Meat-Head** · 1st June, 2020, 09:29 PM

Vague mode on:-

blown fuse

vague mode off:-

**smokinjoe** · 2nd June, 2020, 01:44 AM

All fuses checked and re-checked, since posting I have illiminated the clutch position sensor fault which was due to a broken wire running through the bulkhead but still no start the only faults left are the brake boost sensor and another for the humidity sensor behind the rear view mirror which is damaged due to a previous windscreen replacement, can anyone assist with a wiring diagram for the brake boost sensor as I have 5v and gnd but would like to trace back the signal wire as the 3 wires run back into the cabin area and not directly to the abs pump.
Thanks.

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