Hi 

 

Hopefully someone can help!  My Octavia Mk3 2014 when driving periodically shows a flashing glow plug light and goes into limp mode. Everytime if the engine is turned off and restarted, it no disappears. This can be for a few weeks, or a few days lately. 

 

There is no OBD error code showing though. 

 

Does anyone have any idea what this is / recommendation for what to do?

 

Thanks

What engine?

It’s a 2.0 litre diesel DSG, thanks

On 20/01/2025 at 20:50, JamesWSM said:

Hi 

 

Hopefully someone can help!  My Octavia Mk3 2014 when driving periodically shows a flashing glow plug light and goes into limp mode. Everytime if the engine is turned off and restarted, it no disappears. This can be for a few weeks, or a few days lately. 

 

There is no OBD error code showing though. 

 

Does anyone have any idea what this is / recommendation for what to do?

 

Thanks

Glowplugs do die.  Typically, you get about 130,000 miles on a TDI before they start to show problems.  Get the whole set replaced with good quality parts (e.g. Bosch).  The fact that the issue is intermittent probably highlights an intermittent open-circuit in one of the heater coils.  The car might not throw an error in ODB2 mode, it might be the VAG (history) code memory - for which you will need ODBEleven or VCDS to read.

Edited 22 January, 20251 yr by varaderoguy

A flashing glowplug light does not necessarily mean a faulty glowplug & broken glowplugs should give error codes to indicate which one. (I just replaced one at 256k km)
The glowplug is often used to highlight an "engine fault" which is not emissions related (so does not need to set the  MIL lamp)...

 

Glowplugs are "mostly" only used when the engine is cold, with the exception of regen, so if it happens while drive & the engine is hot I wouldnt rush to change the glowplugs unless you can confirm a fault with a DTC.

 

How are you reading the error codes because if the car is really in limp-home mode or a limitation is being applied there should usually be a DTC to say why?

Thanks appreciate the responses.

 

I have only checked for OBD codes after the engine has been turned off - which clears the flashing the glowplug light on the dashboard.

 

I phoned a Skoda specialist garage and they said that sometimes there is history which only the VW professional readers can read (in their interests to say this of course). I've got it booked in as it needs to be sorted out.

If there was a fault code set it should stay after an ignition cycle but would show as inactive rather than active. 

 

I wonder if it was derrating because of the boost air or intercooler temperature, coolant or oil temp? 

These would not typically show a DTC because it's not a fault rather just a protection of the engine for too environmental conditions.

 

If you have a obd reader you could perhaps try to record some live data of the temperatures to help diagnose the fault?

Edited 23 January, 20251 yr by Gabbo

Flashing glow plug light could be a sticking EGR or inlet valve. They do reset after an ignition cycle until they break or stick permanently. The diagnostic plug in should provide the answer.

Could cold weather have caused this?  Touch wood but it’s been running without issue for a week or so now, so cancelled trip to garage.

 

it did fail to start one very cold morning, Replaced the battery  (original, 10+ years old) and it starts easily now and runs much better.

 

I suppose if light comes back on and weather is not that cold that will answer that.

 

But bar the one time, it has started started and no light. So could regen in cold weather cause it whereas starting in cold weather doesn’t?

 

Thanks

 

 

Have you scanned it with vcds? you need a better scan tool more than likely, there will be a code in there somewhere

I haven't but the lowest cost for one of those seems to be about £400 (not explored all the options). I also have a Superb so have two skodas, but even so, not sure i can justify the cost!

£222 it's listed as on Rosstech website, there are other distributers though.

 

It is essential kit and without it you might as well ask us to guess what colour underwear you are wearing!

There are many cheaper & more modern options to VCDS.

OBD11 being the main contender but also Carista provides similar features..

They do however have annual subscription costs which make them more expensive in the long run but you don't need to continue paying once an issue is solved.

 

I took a Carista Bluetooth adapter (without subscription) for €15 and use an app called Car Scanner (free) which will read and clear fault codes, show live data & everything I've needed recently. 

 

I'm not really sure what "special codes" vcds can read over an OBD2 device?

 

 

I would continue to monitor the situation now the battery has been changed. 

If it occurs again, find someone with a code reader or look at the map of friendly vcds users in your area to try to scan for fault codes.

It's the only way to help pin point the cause of problem area. 

 

As many users have pointed out there are lots of different reasons the glow plug light or check engine light can be illuminated.

16 hours ago, Gabbo said:

There are many cheaper & more modern options to VCDS.

OBD11 being the main contender but also Carista provides similar features..

They do however have annual subscription costs which make them more expensive in the long run but you don't need to continue paying once an issue is solved.

 

I took a Carista Bluetooth adapter (without subscription) for €15 and use an app called Car Scanner (free) which will read and clear fault codes, show live data & everything I've needed recently. 

 

I'm not really sure what "special codes" vcds can read over an OBD2 device?

 

 

Sorry, I should have explained better, when I said 'it is essential kit' I wasn't being exclusive to VCDS,  although £222 I think is an absolute no brainer even if you only ever own 1 VAG vehicle. You can save that money in an instant and many other generic code readers don't offer the same level of test functions and adaptations as VCDS does. As far as codes though I believe OBD11 and Carista will provide the same codes as VCDS will.

12 hours ago, SuperbTWM said:

As far as codes though I believe OBD11 and Carista will provide the same codes as VCDS will

One thing I've found that VCDS does a lot better than ODB11 - is that it shows the part numbers of the modules better.  This is really good for diagnostic purposes, because you can then cross-reference the (old) part number against a new part number etc.

On 30/01/2025 at 05:32, Gabbo said:

I'm not really sure what "special codes" vcds can read over an OBD2 device?

 

OBDII devices only read generic OBD fault codes which are common across all manufacturers, the code will be generic if the second digit after the first letter symbol is 0, these are mainly concerned with emissions and safety systems.

 

VCDS (and others) unlike OBDII can communicate with all the Canbus modules and read all of the manufacturer and vehicle/engine specific codes stored within unseen by OBDII readers, it can do far more than that but that is beyond the scope of your question.

 

On 22/01/2025 at 22:20, JamesWSM said:

I phoned a Skoda specialist garage and they said that sometimes there is history which only the VW professional readers can read

 

Which VCDS is

 

 

 By way of update the fault hasn’t happened again. I cannot prove it,  it there seems to be a correlation between the cold and the fault happening. 
 

I’ve returned the basic OBD reader and if/when needs arises again, I’ll get a VCDS reader. 
 

Thanks everyone for your input.