VW Polo TDI accelerating on its own! Help!

[s3man]

I have a polo 1.4tdi 9n MK6 2003

It has been accelerating on its own. After trying new ECU, Pedal, Convenience Unit etc we still could not find problem.

Then I removed the Fuse for the air conditioning system and it behaves as normal. So 100% related to this as been driving without this fuse for months.

Only problem is Aircon does not work and you cannot change temperature unless you insert fuse, then set temperature and again remove.

I have removed heater panel and changed it, still problem persists.

There are 3 ways to stop accelerating on its own.

1. If I remove aircon fuse (then cannot use aircon or heating control)

2. I remove the Aircon/Heater plug as shown. (then heating control aircon does not work and central locking sometimes stops working)

3. Remove Can bus plug into convenience unit (Central locking/alarm plays up)

I am thinking its a problem with can bus signals. Do you suggest next steps to isolate fault? VAG COM thrown no fault codes.

With the 2 can bus wires pictured (Orange/Green & Orange Brown) is there an input into aircon unit that passes though causing problems?

This fault first came about shortly after changing stereo so possible short to can bus bus mistake?

ANY help would be greatly appreciated!!!

http://i18.photobucket.com/albums/b125/w_ian/1-1.jpg?t=1297013502 (http://javascript%3Cb%3E%3C/b%3E:void%280%29;)

http://i18.photobucket.com/albums/b125/w_ian/2-1.jpg?t=1297013615 (http://javascript%3Cb%3E%3C/b%3E:void%280%29;)

http://i18.photobucket.com/albums/b125/w_ian/3-1.jpg?t=1297013410 (http://javascript%3Cb%3E%3C/b%3E:void%280%29;)

http://i18.photobucket.com/albums/b125/w_ian/4-1.jpg?t=1297013696 (http://javascript%3Cb%3E%3C/b%3E:void%280%29;)

[Meat-Head]

on the bonus side at leat your 14 posts in nearly a year doesn't have as many downloads next to it.

Would suggest fitting the orignal gramma phone bak in.

When you say 'accelerating on its own' all the time, after 10 mins or what?

We did a wireless on one of these a few weeks ago, no problems (unless he crashed)

[s3man]

on the bonus side at leat your 14 posts in nearly a year doesn't have as many downloads next to it.

Would suggest fitting the orignal gramma phone bak in.

When you say 'accelerating on its own' all the time, after 10 mins or what?

We did a wireless on one of these a few weeks ago, no problems (unless he crashed)

Wow that was a quick replay, thanks

The Original Stereo is back in, even tried removing altogether.

It accelerates when you take your foot off the accelerator. Almost always, cold or warm.

Not always the same amount but intermittent for 5-15 seconds (on off/jerky) once you take your foot off

i.e. Coasting down a hill, flat, or to a roundabout.

If you keep your foot on the pedal even slightly, it never does it!

[Liteace]

Have you checked the TPPS, how high does it rev to ?

[Meat-Head]

your second to last picture, the can-lines laughting at you, cut them see what damage it causes.

Ah - Just though, dumb ~~~~.

When you turn the A/C the ecu will jack the revs up 100 rpm.

guess you have a 'crutchless' compresser, - if it turns - the inner - it's ~~~~ed - you need a new one - that's what the rattling noise was lol.

Unplug the trianry switch, then drive, see what happens.

[s3man]

your second to last picture, the can-lines laughting at you, cut them see what damage it causes.

Ah - Just though, dumb ~~~~.

When you turn the A/C the ecu will jack the revs up 100 rpm.

guess you have a 'crutchless' compresser, - if it turns - the inner - it's ~~~~ed - you need a new one - that's what the rattling noise was lol.

Unplug the trianry switch, then drive, see what happens.

Are these not can-bus wires in the picture? I thought it was pointless cutting them if I can just unplug them from their destination (convenience unit)

I am not sure what you mean by rattling noise? I didnt say there was did I?

[s3man]

Have you checked the TPPS, how high does it rev to ?

I have replaced the whole throttle pedal with Positioning sensor built in? Is that what you are refering to as TPPS? Thanks

[Liteace]

does it rev when its stationary on idle or only when your driving it ?

[s3man]

does it rev when its stationary on idle or only when your driving it ?

Only when driving. Its a strange one. I have a feeling its something to do with signals on the Can - Convenience or Can - Low wires (orange ones) as when that block with those two wires is unplugged from the convenience unit it stops doing it.

Obviously then things like aircon/heater/central locking stop working properly.

I do not fully understand the system but assume things are done by sending serial data. I couldnt believe the hot/cold control is done through these wires.

Thanks for your suggestions though I have hit a brick wall

[Liteace]

Main PC has just gone down,so I on laptop (10 inch screen) im working on main now will have a look at wiring diagram when I get it back up and running

[s3man]

Main PC has just gone down,so I on laptop (10 inch screen) im working on main now will have a look at wiring diagram when I get it back up and running

That would be fantastic. I am guessing as I changed the AC/Heater Unit it may be an input going into or passing through it. Maybe I fried something in the Can Bus system when removing the aftermarket radio for original VW. (wires had been cut by previous owner)

Also wheel bearing changed the same day but if it stops when I remove Aircon/Heater/Can bus fuse I doubt its that.

Many Thanks for your help so far. It had been into VW before I isolated the problem but they were quite confused about the problem and advised to change pedal which I did.

[Liteace]

Check you have good can high\low on pins 14 and 6 of DLC, have you changed or checked the ECT sensor, what No A\C fuse do you pull ??

[s3man]

Check you have good can high\low on pins 14 and 6 of DLC, have you changed or checked the ECT sensor, what No A\C fuse do you pull ??

I have changed the Temp sensor as it actually was giving eratic readings which made me think I had found the solution but problem persisted. I will find out what fuse number it is.

How do I check if I have good Can High/Low?

Thanks

[Liteace]

I have changed the Temp sensor as it actually was giving eratic readings which made me think I had found the solution but problem persisted. I will find out what fuse number it is.

How do I check if I have good Can High/Low?

Thanks

You need to scope pins 14 and 6 of the DLC with a dual channel scope and make sure you get a mirror reading, whay engine code you got AMF or BAY ? Like this:

http://www.digital-kaos.co.uk/forums/members/44003-liteace/albums/scope/4557-scope-can-high-low.png

[s3man]

Unfortunately I haven't got a scope.

Its the AMF engine.

I could do with some sort of wiring diagram of the system with aircon/heater or how Can bus is linked together. Could it even be something like an electric window/central locking PCB throwing out unusual serial communication into the can bus system causing misread signals and increasing RPM?

I am 90% sure its to do with Can bus as when I pull Plug containing two orange can wires from the Convenience unit under the steering column it also stops its unattended acceleration.

Many Thanks for your help so far...

[Liteace]

You say you have changed the ECU, what ECU have you changed ??

[Liteace]

Here's a wiring diagram of A\C controllers

[Liteace]

A63 Ac control module
B53 Ac temp sensor
B159 Ac fascia temp sensor
B160 Ac footwell temp sensor
Y156 Ac refrigerant control valve
B161 Ac pressure sensor
M114 Ac heat air mix flap motor
M7 Ac heater blower motor
S292 Ac \heater function cntrol panel
M105 Ac\heater recirculation flap motor
X1 DLC
A130 diag module
A35 engine ECM
M6-1 engine coolant blower motor 1
M6-11 engine coolant blower motor 2
A95 engine coolant blower motor control module
S24 engine coolent blower motor switch
B24 ECT sensor
A162 immo contol module

[catalin]

1) is a good idea to use a vag-com and check mvb 2 :


002 Idling speed
Measured values at idle, coolant temperature min. 80?C:
1) Engine speed
900..0.980 rpm A OK
2) Accelerator pedal position
0.0 % A OK
Above 0,0 % A Accelerator pedal sender incorrectly
set or defective
Open circuit in wiring
3) Operational status
X X 1: AC compressor on (if air conditioner fitted)
X 1 X: Idling speed switch closed
1 X X : Idling speed increased because air conditioner on
(if air conditioner fitted)
0 1 0 : Specification
4) Coolant temperature
80...110 ?C A OK
Less than 80?C A Warm up engine


maybe give you a clue !!
2) did you check carefully for water ingress?

[s3man]

1) is a good idea to use a vag-com and check mvb 2 :


002 Idling speed
Measured values at idle, coolant temperature min. 80?C:
1) Engine speed
900..0.980 rpm A OK
2) Accelerator pedal position
0.0 % A OK
Above 0,0 % A Accelerator pedal sender incorrectly
set or defective
Open circuit in wiring
3) Operational status
X X 1: AC compressor on (if air conditioner fitted)
X 1 X: Idling speed switch closed
1 X X : Idling speed increased because air conditioner on
(if air conditioner fitted)
0 1 0 : Specification
4) Coolant temperature
80...110 ?C A OK
Less than 80?C A Warm up engine


maybe give you a clue !!
2) did you check carefully for water ingress?

Thanks but we have already checked timing a few months back and it was out of range slightly. Now within range but made no difference.

Cannot see signs of water ingress anywhere. Vehicle seems to have been very well maintained and never left standing.

[s3man]

You say you have changed the ECU, what ECU have you changed ??

Changed ECM for identical AMF unit with same part number. Still same problems so have put original back on. Convenience unit also changed.

Thanks for the wiring diagram I will study it well and I may need to ask some questions.


Thanks!!!!

[molla79]

did you look on engine ecu if throttle valve is adapted?
this make often a lot of problem...

[s3man]

did you look on engine ecu if throttle valve is adapted?
this make often a lot of problem...

I thought this was only on petrols? Thanks

[Liteace]

I thought this was only on petrols? Thanks

Did you find out what number fuse for the A\C you pull ??

[s3man]

Fuse 29 - Diagnosis connector / Air Conditioning System 5A

[Liteace]

So when you unplug the A\C - heater contol panel (your 1st post, pic 1) the problem goes away ? The best thing to do is plug it all back in and find someone with a scope to check hi\low can signals on DLC. Have you checked things like EGR, intake manifold air control solenoid and actuator ?

[s3man]

So when you unplug the A\C - heater contol panel (your 1st post, pic 1) the problem goes away ? The best thing to do is plug it all back in and find someone with a scope to check hi\low can signals on DLC. Have you checked things like EGR, intake manifold air control solenoid and actuator ?

Yes when I unplug the plug shown, or the plug going into the Convenience unit under the Steering wheel (containing just 2 twisted can bus wires it goes away.

Yes EGR functioning fine, also tried unplugging it and checking intake manifold, all clean. Where is the air control solenoid or is that the solenoid that moves the EGR flap?

I can try and get hold of a scope.

If I dont see a mirrored image on DLC where do you think the problem would lie?

Many Thanks, I feel we might be getting somewhere!

[s3man]

Can you tell me what A95 is on the diagram? When I take out inputs 3 and 6 from component A95 it appears to stop?

Thanks

[Liteace]

Can you tell me what A95 is on the diagram? When I take out inputs 3 and 6 from component A95 it appears to stop?

Thanks

A63 Ac control module
B53 Ac temp sensor
B159 Ac fascia temp sensor
B160 Ac footwell temp sensor
Y156 Ac refrigerant control valve
B161 Ac pressure sensor
M114 Ac heat air mix flap motor
M7 Ac heater blower motor
S292 Ac \heater function cntrol panel
M105 Ac\heater recirculation flap motor
X1 DLC
A130 diag module
A35 engine ECM
M6-1 engine coolant blower motor 1
M6-11 engine coolant blower motor 2
A95 engine coolant blower motor control module
S24 engine coolent blower motor switch
B24 ECT sensor
A162 immo contol module

[dimitar]

Just to mention ive been having problems with e39 525tds a few days ago similar like yours. The car had a vp37 pump same like VWs the problem was no mater how long you rev the car stationary it works great and as soon as you start driving the revs got stuck at 3000rps for several seconds. After a few days strugling with no fault codes in the ecu, pump ok everything good, it turned out that when i unplug conector from abs module the car works ok. Replaced abs modulator and problem gone. BTW the abs didnt had any fault codes too.Very strange, never had problem similar like this before.

[s3man]

Just to mention ive been having problems with e39 525tds a few days ago similar like yours. The car had a vp37 pump same like VWs the problem was no mater how long you rev the car stationary it works great and as soon as you start driving the revs got stuck at 3000rps for several seconds. After a few days strugling with no fault codes in the ecu, pump ok everything good, it turned out that when i unplug conector from abs module the car works ok. Replaced abs modulator and problem gone. BTW the abs didnt had any fault codes too.Very strange, never had problem similar like this before.

Funny you say that the abs was playing up a few weeks back and I disconnected the fuse from the battery terminal until I had time to look at it.

Unfortunately with the ABS back on, A/C fuse back in the car is now not showing the acceleration problerm.

This was the last thing I wanted to happen as now I cannot diagnose until the problem returns! arrrrrggghhhh!


Thanks for the help, I have a feeling this thread may lie dormant until 'Herbie rides again'!

[s3man]

To help anyone out it was a faulty ABS sensor - Dangerous!

[dopsleutel13]

And you found this after 2 years ? and no errors in ABS ?
:top:

[s3man]

I forgot to update thread. No errors when scanning. Detected by logging ABS sensor speed in VCDS.

[Meat-Head]

So hiw did you find that fault?

[s3man]

Front Left sensor was logging speed intermittently low. Logged with VCDS.