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Discussion Starter #1
2.5tdi 102 auto 1999
So my van has developed an issue where when you press the accelerator pedal it does not rev at all. If you press and hold the engine light comes on.

Starts first time and every time. Never had any issues with it in last 10 years, got 70k on the clock I’ve had it since it had 28k.

i Can’t read the codes off with vcds, will connect but won’t connect to ecu. Tried with 3 different bits of kit with same result.
Tried the following,

Swapped ecu
Swapped accelerator ped

Checked continuity through loom between

ecu- fuel pump
Ecu - accelerator


does anyone have any ideas as I’m loosing the will to live.

Thanks,

jonathan.
 

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The air mass sender on the way in from the air filter, if failed,causes no power but no problem starting .But several other sensors could cause limp mode which is what you describe, I think.More concerning is why you cannot get to read the faults electronically .I had the above fault but I found it immediately using a cheap generic code reader which contacted the ecu (AJT) no problem .My guess is only a guess .Need to get into those DTC codes somehow otherwise you are really in the dark .Perhaps some wise person on the forum can help ?
 

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Discussion Starter #3
Thanks for the response, the issue I am having is not lack of power, it’s that pressing the accelerator pedal has no effect and the engine stays at idle. I agree sorting the connection would help greatly but not sure how to go about it.......
 

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Have you ever made contact with the ecu via your vcds cable or is this the first time you have tried and it has failed ?.Very disappointing if you have paid for vcds and it is not giving a result .One thought is that, in order vary the potential ,which is how the throttle pedal signals the injection pump ,there must be voltage there in the first place .If the circuit is dead (no voltage ) ,nothing is going to happen on the accelerator front .The engine will start. fine because starting and tick over are mechanical not electronic .Dont quite know how you would test this but maybe something to investigate using wiring diagram and multimeter .Also could VCDS supplier help as I read they offer technical support ?Not sure but think the contacts at the pump end of things should be showing voltage when the ignition is on or the engine is running .Just ideas from basic principles ..
 

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Discussion Starter #5
I’ve have two fellow forum members check with their vcds, they could read their vans fine but it wouldn’t mine. Checked the potentiometer in the pedal, will take a look to see re the pump thanks!
 

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As above or it sounds like you have a common earth problem somewhere. Quite a few of the engine sensors use a common earth through the ECU. I would check the ECU earth pin for continuity then work your way through all of the sensors in turn. This should point you to the area of the fault or at least which wires could be suspect.
 

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Just checked with my VAG mechanic son He said first check for resistance between the pedal earth/s & the vehicle body you should be near zero resistance ie no more than 0.1. Then check you have 5 volts from the live feed/s.
 

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There's also a "spider's web" of "earth" terminals next to the fuse unit.....check those.
If you've had a screen leak at any time, or they have been disturbed, they can make bad contact.
Just "wiggle" them, and possibly use some electronic contact spray (NOT WD40).
LOADS of problems seem to pop up for seemingly no reason, when just one of those contacts is "iffy".

BingleyLion is a good bloke to take note of....yet to see him post something NOT useful (it happens with some). :D
 

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Discussion Starter #12
So.... managed to get the code reader to work by pulling a positive feed direct from the battery to the socket. After clearing the codes a pedal feedback one persists. Checked the terminal for the pedal module and I have good grounds and 2 x 5v from the feeds. Trying to get another pedal as I suspect the one the mechanic tried originally was off a manual t4 whereas mines auto. Struggling to get the replacement part. Waiting for vw to come back to me on availability. It’s a 7d2723507h. What a saga.
 

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Discussion Starter #14
Finally sorted it, traced it using the electrical drawings to a break in one of the signal wires between the pedal and ecu. Break was intermittent when checking for continuity using a multimeter and a bit of cable. Pulled a new multi core cable in through the bulkhead and routed between the pedal and ecu. Spliced and soldered the new cable in as close to the ecu plug as I dared and into the plug for the accelerator.

So after 2 mechanics and one auto electrician I managed to sort it. Thanks to Paul at three counties garage for the phone advice which gave me the steer to recheck the harness and not send the ecu for testing.

Oh, got a spare-pedal and cruise control stalk if anyone ones them.
 
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