Starter Interlock Signal driving me mad

[RS4_Dan]

Hi,

new to the site - I bought a cat C 2006 RS4 back in November last year and got it back on the road February this year and I am thoroughly pleased with my purchase

however I have that common Starter Interlock Signal - short to ground fault:

Address 01: Engine Labels: 079-910-560-BNS1.lbl
Part No SW: 8E1 910 560 HW: 8E1 907 560
Component: 4.2L V8/4V FSI ª0080
Revision: --H09--- Serial number: XXXXXXXXXXXXXX
Coding: 01040003180F0160
Shop #: WSC 00191 264 15243
VCID: 63CF981AA2A0032784-8036

1 Fault Found:
005924 - Starter Interlock Signal
P1724 - 001 - Short to Ground
Freeze Frame:
Fault Status: 01100001
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 124928 km
Time Indication: 0

Freeze Frame:
RPM: 833 /min
Load: 12.5 %
Speed: 0.0 km/h
Temperature: 48.0°C
Temperature: 25.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 13.843 V

Readiness: 0110 1101

This is a permanently active fault and brings up the EPC light permanently on. The car starts every time using the button so I cant work out how it can be short to ground?

I have replaced both clutch pedal switches and the start button itself but no joy. I have visually checked the wiring with no signs of damage. So Any ideas? my next thoughts were either one of the two relays, not sure where they are located?

Another question I have is when I select ESP the icon on the dash flashes? is this right? my previous A4 DTM was permanently illuminated when selected until it was called to work then it would flash, before going back to solid illuminated. I have no fault codes logged.

thanks for your help in advance

[MikeFish]

I think the esp light flashes for the 1st stage ie a quick press of the the button, then goes solid when fully turned off ie long press of the button.

Do you have to keep the starter button pressed until it starts or can you press and let go to start?

[RS4_Dan]

Thanks for the quick response.

will check the ESP light as I only ever quick press it - didn't realise there was 2 stages!

as for the starter button I have to hold it down until it starts - it wont start if I just press and let go

[MikeFish]

Ok sounds like you have an issue with the lower clutch switch or the circuit its connected to. You sure you didn't break the new lower switch when you replaced it?

[RS4_Dan]

Thanks

will have a further look at the lower clutch switch and circuit - those switches are pretty simple, so I cant see how you can break them with the twist and fit install. I remember the plunger on the blue switch (other being white) being more sturdier than the original switch due to an up rev in the switch.

[MikeFish]

I broke my first one cos I didn't know you had to press the switch in when twisting.

[RS4_Dan]

well I know I didn't do that!! what's the logic behind that step in installation?

[MikeFish]

Don't know, that's just how the switch works. It won't fully twist without the plunger pressed in. And if its not fully twisted then the switch is hard to press and goes crunch when you press the clutch and its bye bye switch.