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Right, so I installed cruise control in my car on Saturday morning. It was all working perfectly until this afternoon, when the EPC light came on. Cruise completely stopped working - the lamp did not illuminate when I flicked the switch to on. Vag-com showed the fault 16955 - Brake Switch (F): Implausible Signal. Cleared the fault but it keeps coming back after a few miles.

Here's where it gets a bit strange:
The brake lights all work properly.
Even when the fault is cleared, cruise control won't turn on. It's completely dead.
Vag-com doesn't register the operation of the cruise switches.

I'm at a bit of a loss as to what's going on here to be honest. I did splice a wire into the brake light switch wiring at the fusebox, following the instructions of various internet guides, but surely that wire is to turn off the cruise control and so shouldn't be the fault? And even if it was, would that account for the complete failure of the cruise to even turn on?

Can anyone help?

Excuse having to "cut" the picture in two. This forum is a bit weird when you try and post images over 800px in width.



Also, excuse my dodgy handwriting above. And It should say fuse 4 instead of 18 above. The handwritten "diagram" was made before I had access to the original schematics and I was flying blind with nothing to work off.

The wire from T41 (stalk) pin 28 (ignore colours above) is what you will have spliced into the break light switch. This isn't to turn cruise off, this is where the stalk (well cruise control bits) gets it's switched live from (fuse 4 powers the break light switch). So, this wouldn't cause VCDS to throw a code.

I think the culprit is either (or both) of the wires going from T41 pin 26 and/or 29. These both terminate at T6W (CCM, brown plug) pin 3 and also go to the dreaded T11a pin 10. It sounds like something could be wrong over here as T11a 10 provides the "switch off" signal to the cruise control, triggered by either the clutch or brake pedal (T41 pin 26/29). It may be a good idea to do a continuity test between T41 pin 26 and T6y pin 5. The loom should have four diodes, one of them between these two connections. It's been known that Kufatec can be numpties sometimes and put the diode in the wrong way round (http://translate.google.com/translate?a ... 32784.html). If the wiring is fine, this could be the problem, but doesn't explain how the system was working before and died all of a sudden.

Ash

Thanks for the suggestions Ash, I'll definitely give them a go and see what happens.

I've had another small poke around with the laptop and it seems like the problem is that the system isn't actually getting any power. Flicking the switch to on doesn't do anything at all and VCDS doesn't register the operation of any of the switches at all - it just lists them as 'not operational' whatever their position. I didn't realise that the wire to fuse 4 was where the system gets it's switched live from, so it sounds like this might possibly be where the problem is coming from? VCDS is throwing up an error code for the brake switch giving implausible readings - is it likely that the brake switch could be failing which is causing this? I'm 95% sure that the wiring is all alright, so I don't know what else it could be really.

I was so desperate that I even tried uncoding and recoding it, which obviously didn't work...

If the brake lights still work right, I'm surprised that VCDS is throwing that code. But if the stalk appears dead, it could be because it's not getting power. I'd try resoldering that wire and see what happens.

Ash

Which guide did you follow mate?

The guide I did mine with said splice into the rear fog lamp fuse wire to power it

I used both the Kufatec guide and this. Both suggested to use the brake switch for the switched live which is what the factory fitted system seems to use.

I had another fiddle about with it today. Checked the wiring and it all seemed alright, resoldered the wire to the fusebox and now I'm getting an error code from the cruise control along with the brake switch error.

VCDS logs are:

Address 01: Engine Labels: None
Control Module Part Number: 06A 906 032 TL
Component and/or Version: 1.8l R4/5VT G 0040
Software Coding: 11500
Work Shop Code: WSC 78131
Additional Info: WVWZZZ9NZ8Y077091 VWZ7Z0G5755588
VCID: 7BFEE7124375
2 Faults Found:

17977 - Cruise Control Switch (E45): Implausible Signal
P1569 - 35-10 - - - Intermittent
16955 - Brake Switch (F): Implausible Signal
P0571 - 35-00 - -

Readiness: 0010 1001

Tried replacing the brake switch with one from another car to see if it was all some coincidence, but the error message still keeps coming up. Seems like there was some problem with the wiring though, so at least something is getting through to it which is some improvement. VCDS still doesn't register the operation of the switches. The cruise error message suggests either a fault in the wiring or with the switch itself. I'm starting to think that I might have just bought a duff stalk which needs replacing, but not sure if that would also account for the error message on the brake switch, which is clearly fine. Suppose it makes sense given the sudden failure of the entire system...

I'll keep updating this, on the off chance that in the future someone else has this problem.

Hi, as many of you know I have done a number of cruise retrofits avec my dad, I would start by checking the power supply, this is the SB4 connection as shown in the diagram. There is no direct connection to the brake light switch as the ECU gets this info on the CAN BUS - the dash indicator should work once you have 12v on SB4 which I normally take directly from the fuse box. hope this helps

I still think it could be a dodgy loom...

Disconnect T6y (brown connector added to CCM) and replace the cruise stalk with the original indicator stalk. I know it's a bit of a pain, but it shouldn't be that bad of a job as you can still leave the rest of the loom in place. Uncode cruise in VCDS and see what happens.

Oh and FWIW, David's just checked and resoldered the connection to SB4 (fuse 4). SB4 goes straight to the brake light switch. Trace the wire from the back of the fusebox and see where it goes.



it ends at pin 2 in the brake pedal switch (blue/black)

Ash

I havent read all the posts but if u do it the way we did it,u will have no problem,if u want i can send u the exact way to mount it with the cable GRA a step by step guide with pic. did u get the cable GRA from Kufatec?

I got the wiring loom from Kufatec, but I got the stalk from the dealers. Worked out about the same price wise.

I tried unplugging the brown connector from the CCM and refitted the original stalk. Went for a test drive, got a few miles down and just as I thought I'd solved the problem the EPC light came on. Implausible signal from the brake switch again, so the switch doesn't seem to be the cause of the problem (main cause at least). So it looks like there's definitely a problem with the wiring. Brake lights are all working properly, and VCDS shows the switch working properly from the measured values. Still throwing up the same fault though - 16955.

I'm thinking about trying to take the switched live from another source to see if that solves the problem. Thinking about testing it from the cigarette lighter but don't want to splice into wires for no reason... Good idea or not?

What about a switched live from the back of the headunit. I remember seeing you'd done the glovebox light mod. Where did you get the power from (presuming HU loom)? I'd tap into that splice so you're not continuously hacking away at the stock loom.

Ash

I used the headunit loom but it's on a constant live so that it works all the time. There's a switch activated by the glovebox door so it's not actually on all the time.

I could still use it just as a test to see if that solves the problems and take a switched live from the cigarette lighter if it all works properly. Luckily I don't really need to drive it most of the time so having it in bits isn't too inconvenient. Just seriously annoying lol.

Any joy David?

Ash

Unfortunately not. I removed the switched live from the fusebox and connected it to another source, but it didn't solve the problem. Still getting the EPC light on and the brake light fault within about a mile of driving. Cruise still won't do anything at all either.

It's perfectly fine to drive, except the light remains on. Luckily I don't need to use it on a daily basis, so it's kind of become a bit of an extended project. I had a chat with a guy who used to work at VW the other day though, and when I said that I was clearing the fault regularly, he said that sometimes this sort of thing goes away on its own after a bit of a drive. I'll give that a go at the weekend and if that doesn't work then its back to the drawing board. Again.

Holy thread revival Batman!

On the off chance that anybody else tries the cruise retrofit and has similar problems to the ones that I had in the first post, it turns out that the brake light bulbs were causing the issue. Replaced them and all seems to be working properly at last...