Accelerator problem?

Last week the car broke down.

A red warning light came on with several loud beeps. The idle was slightly faster than normal and when I pressed the accelerator peddle there was mainly no response, occasionally it would rev.

I hooked up my Vag com and one of the results was:

18047 - Accelerator position sensor 1/2 (g79/G185)
P1639 - 35-10 - Implausible Signal - Intermittent.

The RAC man that came out got the same result and assured me completely it was the accelerator peddle itself, it being the electronic kind.

I got a second hand one form ebay that was assured was fully working and fitted it; this failed the fix the problem and the exact same problem was there.

What else could this be? is the car not recognizing the 'new' peddle.

Audi A4 B5 Avant year 2000 AJM engine.

Thanks

Vag Com faults found:

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2 Faults Found:
17965 - Charge Pressure Control
P1557 - 35-10 - Positive Deviation - Intermittent
18047 - Accelerator Position Sensor 1/2 (G79/G185)
P1639 - 35-10 - Implausible Signal - Intermittent
Readiness: 0 0 X X X

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Address 08: Auto HVAC Labels: 8D0-820-043-1D.lbl
Part No: 8D0 820 043 Q
Component: A4 KLIMAAUTOMAT D57
Coding: 00044
Shop #: WSC 06325
VCID: 2E53E833EAE29E6E36F-2566

1 Fault Found:
01274 - Air Flow Flap Positioning Motor (V71)
41-00 - Blocked or No Voltage

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Address 35: Centr. Locks Labels: 8D0-862-257.lbl
Part No: 8D0 862 257 E
Component: CV-Pump, Alarm, RC D13
Coding: 13130
Shop #: WSC 06325
VCID: 2F6DF537EDE897663D9-4E42

4 Faults Found:
01371 - Alarm triggered by Door Contact Switch; Driver's Side
35-00 - -
01374 - Alarm triggered by Terminal 15
35-00 - -
01370 - Alarm triggered by Interior Monitoring
35-00 - -
01134 - Alarm Horn (H12)
49-10 - No Communications - Intermittent

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Address 45: Inter. Monitor Labels: 4B0-951-173.lbl
Part No: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00102
Shop #: WSC 06325
VCID: E0CFC60B60B6F81E743-4A3A

2 Faults Found:
01377 - Ultra Sonic Sensor for Alarm System; Left (G170)
27-10 - Implausible Signal - Intermittent
01378 - Ultra Sonic Sensor for Alarm System; Right (G171)
27-00 - Implausible Signal

I see you are not getting any response, maybe because no-one knows much about the throttle system you have.

I would ignore the faults referring to climate control (HVAC), central locking, and alarm systems for the time being. But the new accelerator sensor you fitted seems to be giving an erroneous output. It is possible the replacement unit requires Adaptation, ie. matching its output to the ECU.

Checking my Bentley manual (A4 US models from 1996 to 2001) it seems you have the Electronic Engine Power Control (EPC) (E-Gas) system, but it gives very little information except that the signal from the pedal sender goes to the Engine Control Module (ECM), which controls the throttle valve actuator (which should be on the inlet manifold). However, the position of the throttle valve is not necessarily proportional to the pedal position, as it is also controlled by torque and fuel economy considerations. There are also Adaptation procedures to set the kickdown function for various engines if you have automatic transmission.

I'm afraid it sounds a bit of a can of worms to me, and I hope someone on here who knows the system can help you.

All I can suggest, on the basis that there is less likely to be a problem with the ECU than with wiring, as over 90% of all problems are caused by bad connections, is to thoroughly check all the plug connections on the throttle pedal sensor, the throttle valve actuator, and the ECU for good contact and cleanliness. Do NOT use any chemicals or abrasives to clean plug or socket contacts, they are probably gold or silver plated, and that will ruin the plating which makes the contacts.

You will probably need wiring diagrams to do this thoroughly, although there are probably no intermediate connections between the system components and the ECU, so you may be able to follow wiring by colour codes. Some diagrams are available in the Bentley manual. There are none for diesel engined models, but some control systems are generic, the same wiring and colours being used on several models.

Thanks for the in depth reply.

I have been doing a search and it says it can be water in the ecu compartment from a faulty seal to the oxygen sensor.

I hope it's not the wiring because that looks tricky.

Thanks.

The oxygen sensor is usually in the exhaust system, nowhere near the ECU.
However, there could be water around the ECU, which I think is in the same place as mine, behind the engine in the space between the windscreen and the engine bulkhead, on the LHS (LHS from the driver's seat).
Get rid of any water around any electrical or electronic bits and bobs. Pull apart any affected wiring connectors and make sure they are dry.

Also, the car for a few weeks has been going into lip home mode, which I thought was due to a dirty turbo and was going to make a different thread about, but see it can also be caused by a damp ECU.

I also have a similar problem with a VW Golf (2009). I live in Malawi.

An EPC warning light pops up and then the speed performance is affected such that i cannot not 100km/hr. In addition the airconditioner stops working.

After consulting with the VW dealers, the diagonised that i had a fualty pedal value sensor. We bought a brand new accelerator from VW Woodmead in RSA fitted just after two weeks of good performance the same problems cropped up.

I serched on the internet thats when i came to know about this group. The preliminary indications are that the workshop should perform an throttle body alignment. (TBA) of the new pedal sensor. However i need further information regarding this problem!!

Quote:

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Originally Posted by Boydd

I also have a similar problem with a VW Golf (2009). The preliminary indications are that the workshop should perform an throttle body alignment. (TBA) of the new pedal sensor. However i need further information regarding this problem!!

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Throttle body alignment is done with vag com VCDS, not sure it could cure my problem, but worth a go.

Throttle Body Alignment (TBA) - Ross-Tech Wiki

That may be a good idea. My Bentley manual only covers TBA for cable throttles.

Although it covers the DBW pedal unit it doesn't mention TBA for this sytem.

I was not sure it applied to your car, so didn't mention it, as I didn't want to add more confusion.;)

Update:

Undid the box under the scuttle and it was indeed full of moisture like droplets on a window; moisture was also all over the repays in there.

Not sure if the ECU is contained in that metal box, and don't know yet if the moisture as got in there, unfortunately it means wrestling with the wind screen wipers to have a proper look.

http://i66.tinypic.com/eulu83.jpg

http://i67.tinypic.com/imkrjt.jpg

Update, it did indeed turn out to be moisture in the ECU compartment, specifically the ECU seal between the box and bulkhead; there's also one between the pollen filtre and bulkhead. These perish and allow water in.

So, if you have have the faults in the original post then check for water in the ECU box.

Other symptoms I had.

Erratic windscreen wipers, which didn't rest in the home position but halve way up the window.

Going into limp home mode.

Nothing happens when accelerator pressed even though engines on.

A lot of condensation on the windscreen inside.

Other problems associated with these seals is water on the floor and damp carpets in the cabin, normally in combination with blocked bung/drain holes (one under the battery and one under the brake servo).

Hope this has been of use to others with the same problem and thanks for the help.