Brake switch implausible signal

L

LordTJC

Member
Hi all,

My A2 (2001 TDI) has had the glow plug light flashing for quite some time. The fault code given was for implausible signal from the brake switch. I have changed the brake light switch for a new one, and the fault code has remained. I have cleared the codes with VCDS Lite, but the code immediately comes back. I have copied the VCDS Lite scan from today below.

I have done some research on the forum and tried reseating the brake bulbs, new brake bulbs, disconnecting the clusters, and disconnecting the high level brake light. The flashing warning light and fault code remain. The last thing I am going to try is take apart the original brake light switch and clean the contacts and refit it, though as the new switch didn't work I doubt this will.

I've also got a code for the Yaw rate sensor, on a couple of occasions I've had the offside front brake being applied by the ABS system and then it putting on the ESP warning lights, I don't think this is related to the glow plug light/brake switch issue.

As a priority I want to get the brake switch code sorted, as the MOT is due in about 3 weeks. At this point I'm not sure what else I can look at. Any tips?

Thanks,
Tim

Chassis Type: 8Z - Audi A2
Scan: 01,02,03,08,15,16,17,18,37,45,46,56,57,75,76,77
-------------------------------------------------------------------------------
Address 01: Engine Labels: 045-906-019-AMF.LBL
Controller: 045 906 019 G
Component: 1,4l R3 EDC 0000SG 1281
Coding: 00002
Shop #: WSC 02138
VCID: 19454E679081
WAUZZZ8ZZ1N038524 AUZ7Z0Y1751535
3 Faults Found:
16955 - Brake Switch (F): Implausible Signal
P0571 - 35-00 - -
17571 - Shareware Version. To Decode all DTCs
P1163 - 35-10 - Please Register/Activate - Intermittent
17552 - Shareware Version. To Decode all DTCs
P1144 - 35-00 - Please Register/Activate
Readiness: N/A
-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: None
Controller: 8Z0 907 379 B
Component: ESP 20 CAN V015
Coding: 10758
Shop #: WSC 02154
VCID: 47E1D81F76B5
2 Faults Found:
01130 - ABS Operation
27-10 - Implausible Signal - Intermittent
01542 - Shareware Version. To Decode all DTCs
27-10 - Please Register/Activate - Intermittent
 
Last edited:
Howey said:
How did you sit the switch exactly?

Was it a new switch and which style is it?
Click to expand...
I pushed it into the slot and twisted until it clicked into position (the opposite to removing the original).

It is a new switch. Green in colour and the newer version.
 
Presume the fault disappears with the wiring plug unplugged what this proves I am not entirely sure.
My gut feeling is your switch is faulty where did you get it from?
 
I agree with @Howey on the brake switch. Any idea of make, or where it came from?
I'd run basic settings on the yaw sensor (vcds). It's may just have drifted over time, and needs to be reset.
Mac.
 
Howey said:
Presume the fault disappears with the wiring plug unplugged what this proves I am not entirely sure.
My gut feeling is your switch is faulty where did you get it from?
Click to expand...
I have just tried unplugging the brake light switch and the fault light is still flashing. I tried clearing the code and it won’t clear.

Does this eliminate the switch itself, or will the code stay until a switch with a plausible signal is connected?
 
LordTJC said:
I have just tried unplugging the brake light switch and the fault light is still flashing. I tried clearing the code and it won’t clear.

Does this eliminate the switch itself, or will the code stay until a switch with a plausible signal is connected?
Click to expand...
The fault doesn't clear, with the plug out, because with the plug out, the brake switch is seen by the controller as faulty, (open circuit).
With the plug connected, the fault will not clear, if, as suspected, the switch is faulty.
If you bought the switch from Audi, take it back for a replacement, if it's a no name item, take it back for a refund, and put it towards a genuine one.
Mac.
 
With the switch still fitted correctly to the car. Drive the car around the block while gently steering left and right and braking. This is because a few systems are linked together and all need to learn the new brake switch. Has the glow plug lamp now stopped flashing? If not then suspect either the switch was not set up correctly, is faulty or you have a brake lamp out.
 
LordTJC said:
I have just tried unplugging the brake light switch and the fault light is still flashing. I tried clearing the code and it won’t clear.

Does this eliminate the switch itself, or will the code stay until a switch with a plausible signal is connected?
Click to expand...
On a B5.5 passat unplugging the switch clears the dash fault lamp from memory but it's a fair few moons ago
 
I’ve taken apart the original switch and it had a burnt contact inside. I cleaned it up and refitted but this hasn’t resolved the issue.

I can’t seem to find any genuine switches online. They appear to not be available anymore?
 
I’ve since obtained a Febi switch and I am still having the same problem. I find it hard to believe I’ve got three faulty switches, so either I’m installing them wrong or there’s something else that can cause this error code.

The instructions simply say to push the switch into the mounting hole and twist. Is there something else I’m meant to be doing? The brake lights work when I put the switches in. I noticed the plunger was longer on the Febi switch, I pulled the plunger out on the original switch and tried putting that back in but it was no different.

I’ve tried new switches, reseated the brake bulbs, replaced the bulbs, disconnected the light clusters (probably would put the warning light on rather than off!), and tried removing fuses 30 and 31.

Is there anything else I can try?

Thanks.
 
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