Throttle pedal problems lead to dead ecu

[CupraMVR]

Had problems with my car wont rev touch the accelerator and it will bring the EPC light.So had a look at work with a snap-on scanner which told me the throttle position sensor G-79.Ordered a new 1 from seat and fitted that, reset the codes no lights press the pedal again and light comes back on.Called Seat up and took the car down.they looked at my car on there computers and run loads of different tests for an hour n half.finally came out and said the ECU is dead!!!! It has lost the Positive from the pedal to the ecu so the car does not know what its doing.Car is month outta used car warranty.so im stuck where to go from here.
Any help will be greatly appreciated
Many thanks John

 

[bcstudent]

Time to revive an old thread...

My car is now in limp mode and I'm getting an 'Accelerator Position Sensor (G79) - Signal Too Low' fault. It's my own fault for messing around under the dashboard to get the cables through for the boost and oil temp gauges in the dark. I can't see anything loose but it's a jungle down there. It was fine before, but not so fine now :-(

This is a long shot, but does anyone have any wiring diagrams for the throttle pedal -> ECU for an '04 Leon Cupra?

I'm not very happy with myself!

 

[CupraMVR]

Mine was a brown wire that had snapped !! It was leading from the ECU control box and then thru a black box at the top, under the scuttle panel.take all that off and trace all the wires and make sure there is none broken.

 

[bcstudent]

Nice one, thanks for the speedy reply.

I'm 100% sure it's something I've done as I was working in that area before the fault appeared. There's a blue block connector just on the interior side of the scuttle panel and I think I may have damaged it somehow. It's a complete nightmare to get to though.

I've run out of light for today but I'll be straight in there tomorrow. Fingers crossed.

If anyone has Mk1 Leon Cupra wiring diagrams though, I'd love to know where I could find such a thing.

 

[bcstudent]

Right, so I found a wiring diagram for the AYP engine on SCN and it also has a 6-wire throttle pedal sensor. It seems that it is in fact two three-wire potentiometers in one box.

I'm going to assume I've damaged the wiring to one of the potentiometers and that's causing the low signal. I'm wondering though if it's comparing the two sensors and seeing a difference, or if simply not getting a signal from one of them is enough to flag the fault.

I see there's an 'implausible signal' fault code that is derived from the throttle pedal sensor (G79) too. Is there a more detailed explanation of what generates the fault codes anywhere?

It looks like a difference between the two generates an 'implausible signal' and lack of signal from one generates a 'low signal'.

 

[PlatinumR]

the two potentiometers actually read different values. One reads from low to high and the other from high to low and the ecu uses these to determine what you actually want.
You can see the two readings using vagcom.
A friends S8 had this problem and it turned out to be water around the ecu (common fault).

good luck.

 

[bcstudent]

Cheers. I'll dive in there with VAG-SCOPE when I get home from work and see what they're doing.

Where does the main engine ECU live in an Mk1 Leon Cupra?

 

[bcstudent]

Right, I attacked the car when I got home from work. After a furious amount of dismantling I found the problem to be a....broken wire. As I suspected, when drilling the gromet hole for the boost and oil temp gauge wiring I managed to rip a wire out of its connector. Fortunately the wire was on the engine-side of the loom and access wasn't too bad. One nice neat soldered repair later and the car seems much happier. I haven't driven it yet though, so I may be premature in my celebration. Still, there are no longer any EPC lights or fault codes.

I'm not usually one for rushing jobs and cutting corners and this is an excellent example of why I shouldn't. I'm an idiot.

Thanks to those who offered advice. I'll attach pictures of the damage later.

 

[bcstudent]

Thankfully the car drives fine, apart from some re-learning by the ECU after having the battery disconnected. The following picture shows the problem...

I can also say that I'm very pleased with the Prosport gauges. They look great, seem accurate enough and the boost gauge is very responsive. There was some question about their accuracy on the forum, but I'm going to check mine against a calibrated instrument at work for the hell of it. I saw a peak of around 22psi in the test drive and that matches what was recorded on the last dyno run. For £40 each you really can't complain.

 

[CupraMVR]

Glad your all sorted and happy as larry now, I know the feeling when the car just doesnt rev and is in limp mode.but least your all fixed now. hope u get sum pics of gauges up soon

 

[bcstudent]

I'll get some pics sometime before the end of the weekend if you want some. I'm sure there are loads of Prosport gauge pictures on the forum. They can be bought from here:

http://www.xyberautos.com/catalog/default.php?cPath=40_67

 

[traumapat]

well done for finding the wire

encouraging to hear you praise the prosport gauges as ive some waiting to fit.

be very interested in your accuracy views when youve tested them

 

[mr.chris]

same

hi, i have the same problem and car is booke into the garage tmoz. ive been stressing for how much this is going to cost me all wekend. would u say its worth me trying to do it myself or just take it to the garage. wich if i do i shall be telling him that ive probably drilled into the wires and see if he can fix it befor he starts ordering expensive parts.

Shouldnt do things like this myself

 

[LEE69]

wich if i do i shall be telling him that ive probably drilled into the wires and see if he can fix it befor he starts ordering expensive parts.

Shouldnt do things like this myself

If you know what you've done repair it

 

[mr.chris]

lol. im not a mechanical guy at all an poop myself when i touch somthing wen i dont have a clue. and im guessing to thats what ive done as i was putting my gauge in on friday night. wich i might add they finishd installing it for me coz the dimmer wasnt working and was on all the time and i made a right mess of the wires. went down the road an was dragging like a witches tit. no turbo or anything so my heart sunk. i just dont know if i tell them this then they will repair it of just start ordering away.

 

[LEE69]

You drilled to deep going through for the vacuum hose?

Oh yeah definitely tell them, save you some cash in labour.

 

[mr.chris]

i read a few people had drilled to far so was trying to be carefull and didnt feel anything catch as i was doing it. but by the sounds of it then its not the worst thing that ive done and shouldnt cost to much. fingers crossed. is there anything els that i could of done if not this. the EPC light and the Engine manegment light is on.

 

[LEE69]

What else did you touch (break lol)

Hard to tell from the info given.

 

[mr.chris]

well when the dimmer didnt work i phoned the shop owner i bought it off an he told me to switch the dimmer and live wire as he had a other people had phoned him with the same dimmer problem. wich still didnt work. he's said ive shortend the accelerator pedel sensor. as im aware, the blue and grey wire on the light switch was the dimmer wire. so does that have anything to do with the drilling to far. or have a blown somthing by swapping the live wire round. ive been trying to find a part by putting accelerator pedel sensor in on google to try and find what sort of bill im going to get but cant find anything.
Thanks for any help

 

[LEE69]

Swapping the wires around should have been fine, as long as they were both supplying 12v+
The pedal is around £70 iirc