Sporadic limp mode with NO fault codes or dash lights?

[Dan Morritz]

Hi all - it's been a long time since I last posted here. All has been reasonably fine with our T6 until......

Over the past few weeks our van has sporadically been going into limp mode without any engine warning lights or any faults through Carista. It appears to right itself overnight, but then will randomly cut the power when out on our typical journeys. It's happened about five times in the last couple of weeks and forced us to to limp home each time, and most annoyingly forced us to hire a car for our summer holiday.
Here's the thing though, I've taken it to our local garage (who have been amazing to us for some time) who have tested for air leaks and put the van through a series of tests to see what they could discover, but the van was running well. The mechanic took it for a drive locally, where (thankfully) someone trained could experience the shuddering reduction in power, and drive it slowly back to the garage. With no faults showing up, the garage had to hand the keys back with an Autodata recommendation to contact Volkswagen to request that they 'reprogram ECM with modified software'.

I've taken the van to our local Listers today who told me they can't update or reprogram something that comes without any faults or any known issues... All I know is that we have an unreliable van that puts itself into limp mode without any reasons and has been through the hands of two reputable garages. Is there anyone here who has experienced something.....anything, similar? We have no confidence in driving it at the moment, and with two young girls on summer holidays, it's been a nightmare.

We have a Highline Kombi T6, 2016. Thanks for reading.

 

[mlh677]

I had a very similar fault a number of years ago with a Ford Focus diesel - it was especially terrifying when power dropped off whilst emerging from a junction across traffic, though it could just as easily lose power when cruising steadily on the motorway. Similarly, no fault codes were logged. Just switching the engine off for a short time and restarting would sometimes clear the issue, otherwise waiting overnight as you have suggested usually resolved things for a while.

In my case a failing EGR valve was ultimately responsible. Hope that you get the problem sorted soon.

 

[whodat]

Assuming you are looking for ideas as to why it might be. Just to show how random it might be - unfortunately....
On old T4, had 3 different times when it went into limp mode for no apparent reason.
1) Accelerator pedal needed replacing.
2) Brake pedal needed replacing.
3) I foolishly replaced the windscreen washer nozzle for an unheated (cheaper) version when the original was blocked. Go figure.

 

[Dan Morritz]

I had a very similar fault a number of years ago with a Ford Focus diesel - it was especially terrifying when power dropped off whilst emerging from a junction across traffic, though it could just as easily lose power when cruising steadily on the motorway. Similarly, no fault codes were logged. Just switching the engine off for a short time and restarting would sometimes clear the issue, otherwise waiting overnight as you have suggested usually resolved things for a while.

In my case a failing EGR valve was ultimately responsible. Hope that you get the problem sorted soon.

Thanks for sharing this. Yeah, we're really struggling with being confident with the van at the moment for exactly the same reasons you mentioned (pulling out of junctions or roundabouts are scary when it suddenly enters limp mode!).
In this instance, it's been to our local garage who checked the EGR valve amongst other things, including the turbo etc (which I've read can also throw up similar issues).

 

[Dan Morritz]

Assuming you are looking for ideas as to why it might be. Just to show how random it might be - unfortunately....
On old T4, had 3 different times when it went into limp mode for no apparent reason.
1) Accelerator pedal needed replacing.
2) Brake pedal needed replacing.
3) I foolishly replaced the windscreen washer nozzle for an unheated (cheaper) version when the original was blocked. Go figure.

I think just reading comments that show it can be random and does happen to others is reassuring (and I really don't mean to find satisfaction in other owners similar issues!!) and helps balance my typically emotional response which is to get rid of the van (following a number of issues with many sensors, snapped glow plugs, adblue faults etc), but when this thing runs well, it really is a joy. So frustrated right now.

 

[Dan Morritz]

So as a bit of an update (in case people read this in the future, with similar issues!) Listers have got the van, and have been driving it locally to instigate the problem, but after two days - the bloody van is running like a dream. In the words of whodat (above poster) - go figure.
They are happy to hold on to the van to try and experience the fault and then go from there, but if the van is not throwing up any faults, I fail to see what they will attempt to diagnose...
It's Bank Holiday weekend now, so we'll see how things go next week.

 

[whodat]

Genuinely with you the best of luck, and in a good way - hope it goes wrong whilst the mechs have it.