ACC diagnosis

[Tom Rae]

I have an intermittent fault with my ACC. Is there a fault diagnosis trace that VW can access?

Tom

 

[WelshGas]

I have an intermittent fault with my ACC. Is there a fault diagnosis trace that VW can access?

Tom

Depends on the cause. If it is an actual fault, rather than dirt on the front radar sensor or confusion due to roadside furniture etc: then it might show with a Diagnostic scan with the VW Diagnostic Computer or a DIY scan with something like Carista, plugged into the OBD port.

 

[Wongo]

Safety Critical, I would bite the bullet and book it in.

 

[Tom Rae]

Thanks chaps. It is an intermittent fault (it has happened about four times) which reports ACC not available and front assist inoperative. I have checked the sensor and fastidiously cleaned the face and surround but the fault returned. Despite he fact it was working again, I booked it into the dealer who reported that it was functioning correctly and that they could find no error codes which rather surprised me.

 

[Perfectos]

You can’t have a fault on a van you don’t have yet ? (Profile: “on order”)

I suggest you take photos if it happens again, so you can show the dealer.
intermittent faults are sometimes really hard to diagnose.
However the factory fitted safety function is also shown as an intermittent fault, once you have photos of that not working I would think the dealer would have a duty of care to replace the sensor and check the system fully ?

similarly if it happens again, call VW assist / AA and get them to read the fault code whilst the fault is showing on your system. Take a screen shot of the very nice mans tablet so you have proof of the fault Code.

 

[Alan Andrews]

I had an issue that showed on VCDS but did not show on the VW Garage system. The engineer said that VCDS was more capable than the VW system.

 

[Tom Rae]

I had an issue that showed on VCDS but did not show on the VW Garage system. The engineer said that VCDS was more capable than the VW system.

Erm, what is VCDS? The dealer was not unhelpful and I understand his quandary, I have agreed to take a photo of the MFD when it next occurs, I was just surprised that he could not access a record of the fault on my vehicle.

 

[WelshGas]

Erm, what is VCDS? The dealer was not unhelpful and I understand his quandary, I have agreed to take a photo of the MFD when it next occurs, I was just surprised that he could not access a record of the fault on my vehicle.

It might not be a fault.
Many things can upset the system that depends on sophisticated sensors and the safety default position is to deactivate and notify the driver.
One recent post related to ACC deactivating at the same spot in a contraflow lane in some roadworks on the M6. Otherwise his ACC was working properly.
There is a difference between a fault and deactivating because the information from the sensors is implausible due to some outside interference.

 

[Tom Rae]

It might not be a fault.
Many things can upset the system that depends on sophisticated sensors and the safety default position is to deactivate and notify the driver.
One recent post related to ACC deactivating at the same spot in a contraflow lane in some roadworks on the M6. Otherwise his ACC was working properly.
There is a difference between a fault and deactivating because the information from the sensors is implausible due to some outside interference.

WG, thanks, I did see that post about the contraflow when I was researching but mine is not occurring at the same place and can be operating fine and then it "trips out" leaving me with no cruise facility. It is not the end of the world but I do prefer to use ACC/cruise as my speed can creep up without me noticing!

Tom

 

[WelshGas]

WG, thanks, I did see that post about the contraflow when I was researching but mine is not occurring at the same place and can be operating fine and then it "trips out" leaving me with no cruise facility. It is not the end of the world but I do prefer to use ACC/cruise as my speed can creep up without me noticing!

Tom

In that case besides following the advice above take note of the surroundings when it occurs. Any common factors? Sharp bend, cars parked, overhead power lines etc:.

 

[Perfectos]

Erm, what is VCDS? The dealer was not unhelpful and I understand his quandary, I have agreed to take a photo of the MFD when it next occurs, I was just surprised that he could not access a record of the fault on my vehicle.

VCDS, a very powerful and useful tool for VW vehicles

Ross-Tech: Bentley CD Order Form

 

[soulstyledevon]

Technology, such wonderful stuff........

 

[Tom Rae]

This saga continues. I had a further loss of ACC and phoned the VW dealer who recommended I call out roadside assistance which I did. They plugged in and read the fault codes, P060C Control Unit faulty and P06A6 Sensor reference voltage, I then booked the car in for rectification, or so I hoped. On the way up to the dealer I checked and ACC was still de-activated. I received a phone call saying no codes were showing on the VW system and on a test run the system was working. The Roadside guy had said he would not erase the codes however I understand from VW that the action of reading them automatically erases them. In spite of that, I do have the codes however it would appear that they cannot use them "externally". It would seem that this is going round in circles, has anyone any suggestions as how to progress this? The ACC is now working again but for how long? I use it a lot in Edinburgh's 20 mph traffic. I have a small amount of (quickly diminishing) sympathy with the dealer but I just want my van fixed.

You can’t have a fault on a van you don’t have yet ? (Profile: “on order”)

I suggest you take photos if it happens again, so you can show the dealer.
intermittent faults are sometimes really hard to diagnose.
However the factory fitted safety function is also shown as an intermittent fault, once you have photos of that not working I would think the dealer would have a duty of care to replace the sensor and check the system fully ?

similarly if it happens again, call VW assist / AA and get them to read the fault code whilst the fault is showing on your system. Take a screen shot of the very nice mans tablet so you have proof of the fault Code.

Did all that as you suggested and I have the codes (shown in my post above) but it would appear the dealer needs to be able to read them which starts a chain of events?

 

[Tom Rae]

I further escalated this to VW customer service, guess what, they could not help either. It would appear to me that VW parent company and the dealership will wriggle out of any warranty work if they possibly can. Not a happy bunny but thankfully it is the only warranty issue I have had - so far.

 

[Lightning]

I further escalated this to VW customer service, guess what, they could not help either. It would appear to me that VW parent company and the dealership will wriggle out of any warranty work if they possibly can. Not a happy bunny but thankfully it is the only warranty issue I have had - so far.

When I had a Ghost immobiliser fitted, they started van multiple times while setting it up. The battery voltage must have dropped, as when I drove it away I had the error code stating emergency city braking not available. It came on a few times, but corrected itself after a long drive.
Could your engine battery be low on charge when you get the error?

 

[Tom Rae]

When I had a Ghost immobiliser fitted, they started van multiple times while setting it up. The battery voltage must have dropped, as when I drove it away I had the error code stating emergency city braking not available. It came on a few times, but corrected itself after a long drive.
Could your engine battery be low on charge when you get the error?

Lightning, it could well be something similar however surely they should know that? I can only go by the fault codes identified by VW Roadside Assistance which the dealer and VW UK chose to ignore unless they came up on the dealer system. It has corrected itself and is now okay but I see no reason why it shouldn't happen again.

 

[Lightning]

Lightning, it could well be something similar however surely they should know that? I can only go by the fault codes identified by VW Roadside Assistance which the dealer and VW UK chose to ignore unless they came up on the dealer system. It has corrected itself and is now okay but I see no reason why it shouldn't happen again.

The dealerships are not that well trained, and unless a fault is repeatable in front of them, they will refuse a warranty claim.

 

[Perfectos]

Hi Tom,
just doing some reading on your particular fault codes it would suggest an intermittent fault, which would concur with your experience to date.
the intermittent nature of the fault is probably why the dealer won’t do anything, which is not helpful to you in resolving the issue.

the fault codes you listed appear to be very generic, relating to the PCM power control module), which is another reason why the dealer is probably reluctant to investigate further As this type of fault applies to a non serviceable item.

all I can suggest is you log the fault with the dealer formally in writing and state that you believe the PCM is faulty ( intermittent), ask them to reflash (reprogram) the PCM and should the problem occur again that you wish for the faulty PCM to be replaced (as would be normal practice in diagnosis & resolving an intermittent issue with a non serviceable component). Should it ever re occur you have written proof that is has occurred before which puts you in a stronger position to press for a replacement PCM / Ecu

Volkswagen Transporter P0606: ECM/PCM → Processor Fault | Drivetrain Resource

P0606 is a generic OBD II code. Which means that it has the same meaning for the Volkswagen Transporter that it would for any other vehicle. If your Transporter has P0606 it's highly likely that the ECM/PCM (engine or powertrain control module, they mean the same thing) has failed. The PCM...

www.700r4transmissionhq.com

P06A6: Sensor Reference Voltage “A” Circuit Range/Performance

Error Code P06A6 is defined as Sensor Reference Voltage “A” Circuit Range/Performance. This is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system.

autoservicecosts.com

https://www.engine-codes.com/p06a6.html

P060C Internal Control Module Main Processor Performance

How to easily diagnose, repair, and info on causes of a P060C trouble code that indicates a detected internal control module main processor performance problem.

www.obd-codes.com

https://www.autocodes.com/p060c.html

DIAGNOSTIC TROUBLE CODES

An explanation of OBD-II troublecodes for the uninitiated. All cars are fitted with an OBD system that will go fault at some time or the other so it's imperative to understand and auto diagnostic scan.

volkswagen-polo-highline.blogspot.com

 

[Tom Rae]

Hi Tom,
just doing some reading on your particular fault codes it would suggest an intermittent fault, which would concur with your experience to date.
the intermittent nature of the fault is probably why the dealer won’t do anything, which is not helpful to you in resolving the issue.

the fault codes you listed appear to be very generic, relating to the PCM power control module), which is another reason why the dealer is probably reluctant to investigate further As this type of fault applies to a non serviceable item.

all I can suggest is you log the fault with the dealer formally in writing and state that you believe the PCM is faulty ( intermittent), ask them to reflash (reprogram) the PCM and should the problem occur again that you wish for the faulty PCM to be replaced (as would be normal practice in diagnosis & resolving an intermittent issue with a non serviceable component). Should it ever re occur you have written proof that is has occurred before which puts you in a stronger position to press for a replacement PCM / Ecu

Volkswagen Transporter P0606: ECM/PCM → Processor Fault | Drivetrain Resource

P0606 is a generic OBD II code. Which means that it has the same meaning for the Volkswagen Transporter that it would for any other vehicle. If your Transporter has P0606 it's highly likely that the ECM/PCM (engine or powertrain control module, they mean the same thing) has failed. The PCM...

www.700r4transmissionhq.com

P06A6: Sensor Reference Voltage “A” Circuit Range/Performance

Error Code P06A6 is defined as Sensor Reference Voltage “A” Circuit Range/Performance. This is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system.

autoservicecosts.com

https://www.engine-codes.com/p06a6.html

P060C Internal Control Module Main Processor Performance

How to easily diagnose, repair, and info on causes of a P060C trouble code that indicates a detected internal control module main processor performance problem.

www.obd-codes.com

https://www.autocodes.com/p060c.html

DIAGNOSTIC TROUBLE CODES

An explanation of OBD-II troublecodes for the uninitiated. All cars are fitted with an OBD system that will go fault at some time or the other so it's imperative to understand and auto diagnostic scan.

volkswagen-polo-highline.blogspot.com

Perfectos, firstly thank you very much for such a detailed and helpful reply. It has clarified a number of issues in my mind, that said, I am a lowly consumer and as such I do not really feel confident to make such demands as PCM replacement which is perhaps my point, I should not have to! However broad ranging the dealer is in possession of fault codes albeit second hand from their appointed contractor and could/should act on that? As it is, I have been instructed to ring the dealer the next time it happens and take it in immediately. Due to the intermittent nature, there is no guarantee that the codes will even show then and I could be in Croatia (Covid permitting) so it is hardly a practical solution. VW commercial care have been no help really, simply sided with the dealer and I would expect them to also know the issues/arguments you put forward. I will certainly bookmark your comments and thank you once again.

Tom

 

[Alan Andrews]

Perfectos, firstly thank you very much for such a detailed and helpful reply. It has clarified a number of issues in my mind, that said, I am a lowly consumer and as such I do not really feel confident to make such demands as PCM replacement which is perhaps my point, I should not have to! However broad ranging the dealer is in possession of fault codes albeit second hand from their appointed contractor and could/should act on that? As it is, I have been instructed to ring the dealer the next time it happens and take it in immediately. Due to the intermittent nature, there is no guarantee that the codes will even show then and I could be in Croatia (Covid permitting) so it is hardly a practical solution. VW commercial care have been no help really, simply sided with the dealer and I would expect them to also know the issues/arguments you put forward. I will certainly bookmark your comments and thank you once again.

Tom

As has been suggested, capture a video with sound when it next occurs.

We had an intermittent fault with the entertainment head unit, that could not be diagnosed by VW. It was only by having the videos with sound that convinced them that there was a fault.

They said it was helpful to hear our commentary on the video as it occurred.

 

[Tom Rae]

As has been suggested, capture a video with sound when it next occurs.

We had an intermittent fault with the entertainment head unit, that could not be diagnosed by VW. It was only by having the videos with sound that convinced them that there was a fault.

They said it was helpful to hear our commentary on the video as it occurred.

Alan, I do have photograph of the ACC Deactivated message which only stays on for a short period and required some deft photography but it carried no weight with VW who said in effect, no codes no repair!

Tom

 

[andyinluton]

Perfectos, firstly thank you very much for such a detailed and helpful reply. It has clarified a number of issues in my mind, that said, I am a lowly consumer and as such I do not really feel confident to make such demands as PCM replacement which is perhaps my point, I should not have to! However broad ranging the dealer is in possession of fault codes albeit second hand from their appointed contractor and could/should act on that? As it is, I have been instructed to ring the dealer the next time it happens and take it in immediately. Due to the intermittent nature, there is no guarantee that the codes will even show then and I could be in Croatia (Covid permitting) so it is hardly a practical solution. VW commercial care have been no help really, simply sided with the dealer and I would expect them to also know the issues/arguments you put forward. I will certainly bookmark your comments and thank you once again.

Tom

Tom
Having spent many hours chasing down faults like this on other cars, I know how annoying it is.
If its any help a simple £20 OBD diagnostic reader should let you read those codes yourself. I would be prepared to place a fairly large bet that its a slightly loose connection in the wiring on the rear of the Radar Sensor in the grille.

 

[Tom Rae]

Tom
Having spent many hours chasing down faults like this on other cars, I know how annoying it is.
If its any help a simple £20 OBD diagnostic reader should let you read those codes yourself. I would be prepared to place a fairly large bet that its a slightly loose connection in the wiring on the rear of the Radar Sensor in the grille.

Cheers Andy, there is an outside chance that they have done something like that as it is now working as it should. It is not a major issue, more an inconvenience.

Tom

 

[Perfectos]

Cheers Andy, there is an outside chance that they have done something like that as it is now working as it should. It is not a major issue, more an inconvenience.

Tom

Another factor can be water ingress into wires / joints or the sensor housing itself

 

[Tom Rae]

I am pleased to report that the problem is solved . The problem was not with the California but with the bike rack which I use quite often. Unbeknown to me, both brake lights were not functioning on the bike rack which the system detected and disabled front assist and ACC for safety reasons. All the other lights were checked often and were operating as they should. I am afraid I did not connect the the intermittent fault to when I used the bike rack. As the error was “outside” the core vehicle then it follows that no codes could be found other than the wide ranging codes the AA/VW roadside team found. This issue was very frustrating (both to me and the VW dealers) and I post this in the hope that someone who has the same or similar symptoms can check their trailer or bike rack brake lights!