Accelerator Position Sensor: Implausible Signal (diagnostics on 1.9 TDI 130)

[DALE_AVANT]

Hi All.

Has anyone ever had this code flag up on diagnostics:

18047/P1639/005689 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal.

My Avant runs well (good service history, now on 140k) but has a slight hesitation now and again on brisk acceleration. At first I thought it may rev related as it is between 3k & 4k (I never go over 4k), but as this is the only fault code I have I beginning to think the two could be linked.

Could it be the case that the slight hesitancy might be to do with the pedal position during acceleration, and nothing at all to do with revs??


The Ross-Tech website thinks the following:

Possible Symptoms

• Malfunction Indicator Light (MIL) ON
• Reduced Engine Output

Possible Causes

• Wiring and/or connections faulty
• Faulty ECM
• Faulty Accelerator Pedal

Possible Solutions

• Check Measuring Block Readings for Accelerator Pedal
• Check Voltage Signals from ECM to Throttle Pedal (see factory repair manual)
• Check Wiring and Connectors from ECM to Accelerator Pedal

Special Notes

• There are 2 sensors in the accelerator pedal, both should increase in the same direction as the accelerator is pressed but they have different scales. This means one counts from 0 to 100, while the other one counts from 0 to 50.

• Accelerator Position Sensor faults can be caused by issues with the Oxygen Sensor(s) and it's wiring. Please verify this BEFORE replacing the ECM or Accelerator Pedal. Accelerator Pedal failure is very rare.

Any thoughts would be appreciated folks. The car runs great but this intermittent fault is frustrating!

 

[Turkster]

sounds like your accelerator peddle switch sensor is on its way out, just think of how many times the contact inside it has been swipped accorss the connection board inside it mate, iv got a spare one here if you want to try it.

 

[hades-]

1st off id clear the codes
then drive see if it comes back
you can do an adapt on the APS that may sort it out b4 you buy and fit a new 1

 

[DALE_AVANT]

sounds like your accelerator peddle switch sensor is on its way out, just think of how many times the contact inside it has been swipped accorss the connection board inside it mate, iv got a spare one here if you want to try it.

I may well take you up on that offer mate, much appreciated.

Is the spare you have correct for an A4 1.9 TDI 130? Is it an easy job to swap them over?

Do you have any thoughts on the Ross-Tech info sheet?

 

[DALE_AVANT]

1st off id clear the codes
then drive see if it comes back
you can do an adapt on the APS that may sort it out b4 you buy and fit a new 1

What is an adapt mate, reconfigured through Vagcom?

 

[adamss24]

Taake the ecu out and look at the multicolored plugs under. The one yo want is the red one- check for corrosion on the pins. Clean with brake cleaner and refit. Should cure the issue...

 

[DALE_AVANT]

Taake the ecu out and look at the multicolored plugs under. The one yo want is the red one- check for corrosion on the pins. Clean with brake cleaner and refit. Should cure the issue...

Thank you for the info, where is this located on the A4?

 

[DALE_AVANT]

Tried to check out the ECU today but couldn't get to the 4th bolt holding the cover down. Seems as though you have to remove the trim beneath the windscreen and wipers to get to it??

 

[blucoop]

no you dont need to remove the trim, just the drivers side wiper, then you can get at the last screw.

I had similar probs to you and it was indeed corrosion in said plug !!

the seal on my ecu box had gone and so i had to replace the whole box!!! sorted now !!!

 

[DALE_AVANT]

Thanks blucoop, I'll give that a try. I undid three of the bolts and opened the box enough to peep inside lol

 

[DALE_AVANT]

Do I just remove the wiper arm itself? How will that offer me access to the 4th ECU screw?

 

[blucoop]

you can get access (albeit awkward) through the hole that is left by removing the wiper arm.

Pop off the bolt cover on the wiper, undo the bolt then be prepared to f*** about for ages trying to get the wiper arm off.. I spent ages getting mine off, a friend finally got it off using a pulling tool!!!

 

[DALE_AVANT]

you can get access (albeit awkward) through the hole that is left by removing the wiper arm.

Pop off the bolt cover on the wiper, undo the bolt then be prepared to f*** about for ages trying to get the wiper arm off.. I spent ages getting mine off, a friend finally got it off using a pulling tool!!!

Haha oh good, something to look forward to then! Cheers mate, I'll give it a go

 

[DALE_AVANT]

Due to the weather, I still haven't checked the accelerator pedal sensor or the ECU contacts.

Just wondering if anyone has had any more thoughts on the Ross-Tech info above (post #1)?

 

[tommytonguedj]

you can get access (albeit awkward) through the hole that is left by removing the wiper arm.

Pop off the bolt cover on the wiper, undo the bolt then be prepared to f*** about for ages trying to get the wiper arm off.. I spent ages getting mine off, a friend finally got it off using a pulling tool!!!

I Tried to check my ecu when the plenum chamber was full of water an hour i tried to remove the wiper arm in the end i put the bolt back on and gave up lol. What pulling tool did he use??

 

[BA4]

I had one in the garage and I ended up re wiring the accelerator pedal to the ecu, found short circuit, I thinki had the same fault as yourself but I can't remember, hope this helps

 

[DALE_AVANT]

Is the pedal and sensor assembly relatively easy to remove so I can check it's condition?

 

[murran]

have you disconnected, checked and cleaned the coloured plugs at the back of the ecu box yet?

these plugs connect the engine loom to the body loom. all the 6/7 wires from the pedal sensor go thru the plugs. any corrosion in the connections will cause resistance and **** up the signals/voltages.

even if on pulling them apart they look ok.... give them a decent squirt with brake cleaner and blow them out. quick squirt of wd40 and plug/unplug them a couple of times.
then try it.

get a new top and bottom box from tps and replace it.

 

[DALE_AVANT]

I haven't yet mate as it's a pain to get to with the rain etc.

Hence why I would prefer to start my search at the pedal end

 

[DALE_AVANT]

Also, once the pedal is off, can I open the sensor to check for wear/corrosion etc?

 

[murran]

much more likely to be those plugs tho. its the first thing id be checking if your car was in at our garage.
the pedal sensor is very reliable tbh, i wouldnt go taking it apart.

 

[DALE_AVANT]

OK, I appreciate the info :icon_thumright:

If tomorrow can stay dry I'll get stuck in

 

[DALE_AVANT]

get a new top and bottom box from tps and replace it.

Obvious question I'm sure, but why would I need to replace the box?

 

[DALE_AVANT]

Just to add, I have found this thread useful:

http://www.audi-sport.net/vb/a4-a4-...g-engine-light-flashing-cause-fix-inside.html

 

[DALE_AVANT]

have you disconnected, checked and cleaned the coloured plugs at the back of the ecu box yet?

these plugs connect the engine loom to the body loom. all the 6/7 wires from the pedal sensor go thru the plugs. any corrosion in the connections will cause resistance and **** up the signals/voltages.

even if on pulling them apart they look ok.... give them a decent squirt with brake cleaner and blow them out. quick squirt of wd40 and plug/unplug them a couple of times.
then try it.

get a new top and bottom box from tps and replace it.

OK I did this today (apart from replace the box). Took both parts of the box out and checked the seals, seemed OK. Added a bit of Vaseline to the rubber seals to shore things up until I replace.

Sprayed the 4 plugs and sockets with electrical cleaner but they all seemed mint anyway.

Put it all back togetether just as it started raining.

Went out for a 10 mile drive with plenty of beans and guess what.................still does it DAMMIT.

In 3rd or 4th, as you accelerate past 3k revs, it can stutter and sometimes goes into safe mode.

What now guys?!

 

[murran]

do you have fascility to check the actual values coming from the pedal sensor?

 

[DALE_AVANT]

do you have fascility to check the actual values coming from the pedal sensor?

The only info I have is:

18047/P1639/005689 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal.

Along with:

P1639-35-10 or P1639-35-10.

Readiness: 0 0 X X X

Any use?

 

[murran]

not really.
reading the values thru the engine ecu via the diagnostics while driving the car. then comparing the voltages via back probing the signal wires with a multimeter would tell me whats actually going on.

failing that, if i was in your position now having ruled out the likely plugs in the ecu box.... being that its so easy (three 10mm nuts and a plug) to swap out the pedal sensor unit.... would be to find another willing forum user local to you, that you could drive to, to then swap your pedal sensor unit with and go for a drive (to see if its that) before buying a new one.....
the pedal unit would be the last suspect in my experience!

 

[adamss24]

Same here, as i said above and murran confirmed, i would check the wiring first and only move to the pedal in the last instance. Had a passat b5.5/2002 which used to do the same only on high speed, changed the boost control valve, accelerator pedal, cleared the connectors inside the ECU and according to the owner it was still doing it but very rarely and it was just a stutter in 6th speed at motorway speeds ! Thing is that i never experienced the said stutter even on extended drives and i suspected the chap was driving in high gear under- revving the engine hence the stutter as the PD engine does not like being under-revved !

 

[DALE_AVANT]

Unfortunately I have neither diagnostics equipment or a multimeter so I expect a quick swop over of the unit will be my best bet at this stage.

Do I need to remove any trim etc or are the three retaining nuts all accessable from the drivers footwell?

not really.
reading the values thru the engine ecu via the diagnostics while driving the car. then comparing the voltages via back probing the signal wires with a multimeter would tell me whats actually going on.

failing that, if i was in your position now having ruled out the likely plugs in the ecu box.... being that its so easy (three 10mm nuts and a plug) to swap out the pedal sensor unit.... would be to find another willing forum user local to you, that you could drive to, to then swap your pedal sensor unit with and go for a drive (to see if its that) before buying a new one.....
the pedal unit would be the last suspect in my experience!

 

[DALE_AVANT]

Anyone know the procedure for removing the pedal assembly (to check the contacts and part number)?

 

[murran]

you open the drivers door and bend down to look at it.
then assess whether you can get to the three 10mm nuts to remove the pedal unit without removing the lower dash board trim.
if you cant then theres not much more work to remove the trim. bob the end cover off the dash to access the 2 8mm bolts and under the trim youll spot some more.

 

[madcustomer]

you open the drivers door and bend down to look at it.
then assess whether you can get to the three 10mm nuts to remove the pedal unit without removing the lower dash board trim.
if you cant then theres not much more work to remove the trim. bob the end cover off the dash to access the 2 8mm bolts and under the trim youll spot some more.

Appologies for jumping in on someone elses thread but I too have the same fault code, no water issues as all this has been thoroughly checked.
So decided to swap the pedal assembly.

Had a bash at this today, removing the lower trim panel certainly makes access 100% easier!

Got the old pedal off and had sourced a spare from eBay, however on closer inspection the part numbers were slightly different.

Part number from new part is 8E2 721 523 D (Manufacture date 01 21/03)
My old part number was 8E2 721 523 C (Newer manufacture date iirc 01 11/04)

On fitting the new pedal plugging back in, I started the car and upon pressing the pedal the car went straight into limp mode.

Is there anything I've missed - any reconfiguring need to be done?

The car is an Audi A4 Avant tdi 130 on a 54 plate.

Thanks in advance

 

[murran]

if the part number of your old unit has been superceeded then tps should be able to tell you.