Brake switch implausible signal

Read again Mac

176 Earth Connection In Right Headlight Wiring Harness.

This earth is also connected to the Earth Point Lower Part Of Right A Pillar.

Neither of these are the main earth that bolts below the left headlight.
 
audifan said:
Read again Mac

176 Earth Connection In Right Headlight Wiring Harness.

This earth is also connected to the Earth Point Lower Part Of Right A Pillar.

Neither of these are the main earth that bolts below the left headlight.
Click to expand...
Edit: I just read through my recent posts, I did not mention the left headlight.
But both (right headlamp and right A pillar) are relavent to the problem. If the switch has a poor ground, it will not operate correctly.
Mac.
 
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PlasticMac said:
Check your spare switch with a meter, to see if it conforms to "With the pedal at rest the switch pins 1 and 4 (red/brown and red black) are open circuit, while pins 2 and 3 (red/green and white/red) are closed.
You could link pins 2 and 3 on the connector, this would mimic the switch, as it should be, If the fault does not clear, then maybe it's not the switch at all.
I also think the switch shares the ground behind the headlight ...
Mac.
Click to expand...
I have tried bridging pins 2 and 3. The light still flashes and error code remains. Looking on the measuring block it still shows 010. If I bridge pins 1 and 2 it alternates between 010 and 011.

So we have narrowed it down to the middle two pins, and the wiring on the car being the issue.

I think my next step will be to find the Earth points discussed.
 
I've been studying the circuit diagram again.
The left hand side of the switch, which is normally open circuit, and closes when the pedal is pressed, operated the stop lamps.
The right hand side, pin 2 goes to earth in A pillar, and pin 3 goes to the injection controller, (I'm guessing it closes the injectors when braking).
I can't see that a problem with the left hand side, controlling the stop lamps, would cause the error your seeing.
So, I agree it's probably wiring, earth to pin 2, or pin 3 to the injection controller.
Mac.
Edit: Pin 3 on the switch goes to White/red wire, pin 65 on the injection controller. So you should be able to check with a meter, on ohms, that there is an earth on pin 65, white/red, at then controller.
 
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Well as you have tried various thing why not just follow the manual instructions...

Audi Workshop Service and Repair Manuals > A2 > Brake system | ABS, ADR, TCS, EDL, ESP | Removing and installing components of the ABS/ESP system, ITT Mark 60 | Adjusting brake light switch

A2 > Audi Workshop Service and Repair Manuals > Brake system | ABS, ADR, TCS, EDL, ESP | Removing and installing components of the ABS/ESP system, ITT Mark 60 | Adjusting brake light switch
workshop-manuals.com

These are the instructions for the MK60 ABS.
 
audifan said:
Well as you have tried various thing why not just follow the manual instructions...

Audi Workshop Service and Repair Manuals > A2 > Brake system | ABS, ADR, TCS, EDL, ESP | Removing and installing components of the ABS/ESP system, ITT Mark 60 | Adjusting brake light switch

A2 > Audi Workshop Service and Repair Manuals > Brake system | ABS, ADR, TCS, EDL, ESP | Removing and installing components of the ABS/ESP system, ITT Mark 60 | Adjusting brake light switch
workshop-manuals.com

These are the instructions for the MK60 ABS.
Click to expand...
Thanks. I've already tried that, though I couldn't find any adjusting instructions at the time.
 
I have today spent some time on the car. I created a new earth connection between Pin 2 on the switch connector and the earth I use for my dashcam, this didn’t change anything. I have also checked for continuity between Pin 3 on the switch plug and Pin 65 on the ECU connector. This had continuity.

I have connected VCDS with my extra earth connection in place and the measuring block still shows 010 while the brake pedal is not being pressed. The error code will still not clear.

Does this leave the ECU being at fault? When I tested measuring block 003 on the ABS ECU, it appeared to be getting a changing signal between activated and not activated when I push the pedal. I'm assuming the ABS ECU must be getting this from somewhere else not involving the brake light switch.

Again thanks for everyone’s help.
 
You said the pedal was not pushed when you fitted the switch. That is why I asked you to follow the fitting instructions. May solve the issue, may not but at least you can say it was done by the book.

Remove and check the brake light bulbs for the centre contact wearing. If so fit new bulbs ensuring they make good contact to both their connectors. Do you have any other issue with the rear lights and are the connections all free from moisture?
 
Sorry if this is unrelated or unhelpful, doesn't the ESP light also come on/off when the brake light switch is failing intermittently on the petrol A2's
 
Not sure if each half of the brake switch give a different lable after the line in the error report "Component:"
The side that goes to the ECU controls the injectors, I think, shutting them down with brake is pressed.
The other side controls the brake lights, and, guessing again, the ABS.
If anyone has Scan log, relating to the brake switch, could they check what's after "Component: please?
Mac.

Edit : Just found this on Rosstech forum, spotted the P0571, as in the first scan. Maybe points to the light side of the switch, not the ECU side:

EOBD II Error Code: P0571

Fault Location:
Brake Light Switch (F) - Circuit Malfunction/Implausible Signal

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.
Glow Plug Indicator Light (K29) active.
Brake Light(s) not working.

- Fuse(s).
- Wiring/Connector(s).
- Wrong Brake Light Bulb installed (21W instead of 5/21W).
- Brake Light Bulb(s) faulty.
- Brake Light Switch (F) faulty.
- Misadjusted brake switch.
Mac.
 
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PlasticMac said:
Not sure if each half of the brake switch give a different lable after the line in the error report "Component:"
The side that goes to the ECU controls the injectors, I think, shutting them down with brake is pressed.
The other side controls the brake lights, and, guessing again, the ABS.
If anyone has Scan log, relating to the brake switch, could they check what's after "Component: please?
Mac.

Edit : Just found this on Rosstech forum, spotted the P0571, as in the first scan. Maybe points to the light side of the switch, not the ECU side:

EOBD II Error Code: P0571

Fault Location:
Brake Light Switch (F) - Circuit Malfunction/Implausible Signal

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.
Glow Plug Indicator Light (K29) active.
Brake Light(s) not working.

- Fuse(s).
- Wiring/Connector(s).
- Wrong Brake Light Bulb installed (21W instead of 5/21W).
- Brake Light Bulb(s) faulty.
- Brake Light Switch (F) faulty.
- Misadjusted brake switch.
Mac.
Click to expand...
@LordTJC Do you have cruise control?
Mac.
 
audifan said:
You said the pedal was not pushed when you fitted the switch. That is why I asked you to follow the fitting instructions. May solve the issue, may not but at least you can say it was done by the book.

Remove and check the brake light bulbs for the centre contact wearing. If so fit new bulbs ensuring they make good contact to both their connectors. Do you have any other issue with the rear lights and are the connections all free from moisture?
Click to expand...
It was in post 29. I’m going back over the lights side of the circuit again today. No other issues with the rear lights and I haven’t seen any moisture.
 
Yes I did see in post #29 that you pressed the pedal down then fitted the switch but did not see where you ensured the plunger on the switch was fully extended first.
 
LordTJC said:
It was in post 29. I’m going back over the lights side of the circuit again today. No other issues with the rear lights and I haven’t seen any moisture.
Click to expand...
Do the brake lights, left, right, and high level, work while the fault is present?
Mac.
 
audifan said:
Yes I did see in post #29 that you pressed the pedal down then fitted the switch but did not see where you ensured the plunger on the switch was fully extended first.
Click to expand...
Ah I see. That’s what I meant by releasing the pedal onto the (extended) plunger. I tried it on both switches.
 
Can you have another VCDS scan done on the car - well two actually after clearing the faults individually in each module - then a second one and post the results here listing each fault.

The underfloor compartment under the passenger side is completely dry as are all the electrics in there?


Really starting to think that some other system needs a signal from the brake system and is not receiving it.

Has any other work been carried out on the car?
 
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