Diagnostics still on despite changing brake switch

[glennethwest]

Hi,
I'm after a bit of help if possible.

I recently bought a 2002 406 HDI and took it to a 'specialist' in Huddersfield who told me that the reason I keep getting "Anti Pollution Defective" message was because my brake switch was faulty.

I changed the brake switch a couple of weeks ago and I still get the warning message.

Does anyone know how I can solve this? Should the error go away if the fault is fixed?

I'm also thinking of buying this so that I can sort my own 'errors' out - any advice is welcome! http://cgi.ebay.co.uk/USB-OBD-II-ELM327 ... 385wt_1137

[legoless]

Hi Glen
Welcome to the forums
I would be surprised if a brake fault would give rise to an anti polution one
Its very hard to get a code reader that reads pug codes correctly, if you do a search on here for code readers you will soon be up to speed on what works and how muchit will cost.
In my opinion the best thing is get them read by a dealer as and when you need to as they have the experience.
There can be a lot of causes for the warning.. some of which can appear regularly on these forums. Do search and then I expect you will be able to narrow down the likely causes and then ask away on here
Al

[Doggy]

Hi glen & welcome to the site

It may help if you let us know which version of HDi you have, (there are 2.0 90bhp & 110bhp versions, plus a 2.2 136bhp). The Antipollution Fault message covers anything engine ecu related, (though it's difficult to see how a stop-light switch could be relevant).

Don't know about the ELM327's - I believe they will work to a very limited extent on HDi's though maybe not straight out of the box. (Read something on the 406 coupe site about this, you could try searching for ELM327 on there).

The 'proper' gadget is a Lexia interfaced / PP2000 software, which you can get a copy of on Ebay for around £150. Some other readers can definitely get you the fault code(s), but not the diagnosis, AFAIK.

Guessing you're in the Huddersfield area? (helps if you put your location in), maybe someone nearer can help?

[glennethwest]

Thanks to both of you on this one.

I have a 2.0 (110) HDI Executive.

I bought the car second hand with the fault on it already. I took the car to 'canyondust' in Huddersfield who did the diagnostics and told me that there was no given fault. His diagnosis was that it was a faulty brake switch which was causing the car to think it was driving with the brakes on - therefore burning fuel and braking at the same time. He cleared the fault but it came back.

The car has about 188k miles on it (mainly motorway).

Thanks,
Glen

PS - I'm in sunny Dewsbury.

[Doggy]

Sounds a little tenuous to me. Maybe a 2nd opinion?

One possibility. In some cases, if you have an intermittent fault the light will come on and remain on for a number of fault-free journeys, before turning itself off. In a case like this there might not be anything to see, but PP2000 seems to find & distinguish between permanent and intermittent faults pretty well.

If it's only a nuisance, I'd be tempted to leave it until something else develops, or you get an opportunity for a free / low-cost diagnosis.

[steve_earwig]

Remember Sirwiggums brake switch problems a while back? Although I don't think he mentioned any warnings, just weird power/idle issues. So not so tenuous anyway.

The anti pollution warning comes up for all sorts of reasons, it could be a whole lot of stuff and you might have to replace half the engine before you find it. As Dogslife says, ignore it 'til it manifests itself in a more apparent manner

[glennethwest]

Ok Gents, thanks for your help.

The only other thing that is 'wrong' with my motor is that every now and again it idles at around 1100rpm and the cruise control doesn't work.

I've had all the switches out from underneath, cleaned them and re-attached.

I might invest in a diagnostics kit once I've saved up a little - I don't think my wife would appreciate me spending £££s on car diagnostic kit!

Glen

[Springnuts]

... the cruise control doesn't work

Two ideas ...

1) apologies for the first but there is an on/off switch for the cruise control and it is hard to see - just by the dashboard fuses. I only mention it because my cruise control stopped working shortly after we got the car but it turned out to be ...

2) some of the under-bonnet wiring goes round sharp corners, so can break internally - a b****r to find the faults as the wire will make good contact if bent like this, but nothing if bent like that. And sometimes it bends like this when the bonnet is open, but closing the bonnet seems to bend it like that.

Good luck!

Springnuts

[sirwiggum]

Remember Sirwiggums brake switch problems a while back? Although I don't think he mentioned any warnings, just weird power/idle issues. So not so tenuous anyway.

The anti pollution warning comes up for all sorts of reasons, it could be a whole lot of stuff and you might have to replace half the engine before you find it. As Dogslife says, ignore it 'til it manifests itself in a more apparent manner

My issues were the clutch switch, which is similar to the brake switch but sits above the clutch pedal (obviously ).

No warnings, the only warnings I got were if I disconnected the clutch switch, at which point the Anti-Pollution would show when I dipped the clutch coming to a stop (obviously realising it is idling but the clutch switch is not returning anything) and occasionally stall.

My biggest symptom was a 1500-1800rpm hesitation/"misfire" when changing gears.

Switch itself was a few pound, though the particular vendor I used charged a fortune for "courier" delivery. It arrived 4 days later in a Royal Mail 1st class padded envolope.
Easy enough to fit, just slightly fiddly.

[Welly]

The occasional high idle is normally caused by the wiring plug on the throttle position sensor (the one with the accelerator cable going to it, up behind the battery area) just give it a wiggle and it should settle down - you never know it might cure the other fault too!

[Springnuts]

the throttle position sensor

That's the one where the wiring gets bent like that!