Throttle position sensor - strange fault

[Ants]

Hi all, I have recently aquired an A6 year 2000 1.9tdi 110. Whilst driving I lost all power and pulled over, accelerator pedal was dead, engine just idled. Turned off, restarted, and could rev engine again, but as soon as went to pull away throttle control died again, and engine light came on and revs went to 1200 (presume a limp home type mode). RAC came out, there computer read error P1639 throttle pedal position sensor Implausible Signal. To cut a very long story short I have taken pedal sensor apart and cleaned, but all seemed ok, it did then briefly work for a few secs, but dead again, pursaded Audi to lend me a new pedal / sensor to test it with, plugged that in, still no change, and actually then noticed that teh exsiting pedal assemble was quite new, found receipt for it in history showing it 6 months ago from indy garage, so its definatley not the pedal / sender, and cable and connectors all looks good also. Audi diag computer confirms same error code. Another RAC guy suggested that maybe its actually engine throttle sensor thats at fault rather than pedal, we couldnt see anything obviously as a throttle sender on the injection pump assembly but he thought it might be the part circled below:


so I removed it, it has lots of wired going into pump so would come off very far, but alot of fuel came out, so none the wiser I put it back, and car then worked perectly!

So what is that part, and should it have diesel sitting behind it? Of course it could be coincidence that car worked ok after removing it, but after not working all day despite clearing codes, removing power, chaning pedals etc, it seemed odd that it then worked for 300 miles to home.

Obviously I need to get to bottom of it before I can use car for fear of it breaking down.

Unfortunatly still awaiting VAGCOM cable to arrive so no home diag yet, unless anyone is around somerset area and fancies a play with it?

ANY tips of suggestions appreciated!

Thanks Anthony

[bora(ing) nick]

I think devonutopia has vagcom.... it might be worth PM'ing him (Hope i'm not talking "out of turn")

I think the diag will only throw up the same faults as the RAC code reader though.

Good luck

Nick

[Peter D]

It contains, the fuel temp sensor, a metering adjuster, a Modulating piston movement sender, Commencement of injection valve, Fuel shut-off valve. You may have isturbed the fault although any of those sensors would have flag an error code is missing/ out of limits. Regards Peter

[Ants]

Hi, I have found an Audi TSB on it, so guess I am not the first this has happened to. One of the things it suggestes is to check the white connector under ECU, so had ecu out, little bit of water in bottom of black plastic housing (housing broken where it is fixed to chassis, someone has had it out before, broken it,a nd just thrown it back together), and one of the pins on the white plug shows slight green oxidisation. Connectors look ok but obviously signs of water around there, and it was raining hard when it broke down, so I am hoping that it was water ingress causing messed up resistence readings to ECU. Have mended box and applied silicone and large washers around fixing points to prevent water ingress in future. fingers crossed thats it.

Just thought I would report it back for those interested / future refverance.

Thanks Anthony

[andrzej1978]

I have exactly same problem on my A4 2002, when it rains heavily my car goes into limp mode. Had the same error code due to pedal sensor so bought a brand new pedal but that didn't work.It rained again and yet again the same problem. Audi are useless have no idea recommend buying this part and that part reluctant to buy parts willy nilly as i'm sure that this is an electrical fault due to water going in somewhere. But have now read about the water leaking in. So covered the ecu with an old blanket. Problem was better with normal rain but when floods and heavy splashes from lorries it happened again. rah, and stranded doing 40 mph for 25 miles left of my journey. Unfortunately cannot afford to have one car for the dry and one car for the wet.

Hi, I have found an Audi TSB on it, so guess I am not the first this has happened to. One of the things it suggestes is to check the white connector under ECU, so had ecu out, little bit of water in bottom of black plastic housing (housing broken where it is fixed to chassis, someone has had it out before, broken it,a nd just thrown it back together), and one of the pins on the white plug shows slight green oxidisation. Connectors look ok but obviously signs of water around there, and it was raining hard when it broke down, so I am hoping that it was water ingress causing messed up resistence readings to ECU. Have mended box and applied silicone and large washers around fixing points to prevent water ingress in future. fingers crossed thats it.

Just thought I would report it back for those interested / future refverance.

Thanks Anthony

[gajjii]

Have a similar fault on my 2000 A3 1.9tdi (A4 engine). VagCom 1639 code is the only one showing, limp mode with flashing glow plug light. Checked the obvious wiring, no signs of damage/wear.
The pedal sensor indications on VagCom (measure group 062) all look ok.

There are two large plugs on the front of the ECU, is there another one at the back (white)?
How do I get the ECU out?

[AudiQuattroChap]

Hi
I have this problem on my 2003 A4 1.9tdi 130 PD Quattro Avant
Had a really wet day and went into limp mode, flick key on off and would go again, this worked for a bit now stuck limp mode saying throttle peddle sensor but keep reading it’s not on sites and I did suffer water in car from ECU area when drain plugs holes blocked.
How do I get it going again ?
I thought it was turbo so cleaned it out and reassembled but laptop says P1639