For some time now I have noticed that the cooling fan on my 2012 Superb 2.0 Tdi 170 will continue to run after I have turned the ignition off.  My understanding of this is that the engine is attempting a regeneration of the dpf filter (Please correct me if I am wrong).  Having returned from a 2500 mile round trip to the South of France I would have hoped that it may have gone some way to curing the problem.  For most of these miles the car has sat at 80 mph on the motorway.  However upon getting home and simply pottering around town when I turn off the engine the fan is once again continuing to run.  I have found that when it does this if I start the engine and then switch it off the fan will stay off.  In addition to this I observed on my return journey that the water temperature generally was below 90 degrees hovering around 80 degrees sometimes as low as 75. Could this be because the cooling fan is constantly on? On occasions it would get to 90 but wouldn't stay there.  Of all the VAG vehicles I have had the temperature needle is glued to 90 once it is warm, never budging.

Having borrowed a very basic diagnostic tool from a friend it indicated that an Exhaust Temperature Sensor may be at fault.  Does this sound about right?

 

Where do I go from here?  Are there any trustworthy Skoda/VAG engineers in the Peterborough area?

 

Any suggestions would be greatly appreciated.

PS. Current mileage is 160K

 

Get a proper diagnostic scan done and go from there. There's a thread in the diagnostics forum which has a list of people with VCDS who are willing to help other members - you may find someone near you.

4 hours ago, Junips99 said:

For some time now I have noticed that the cooling fan on my 2012 Superb 2.0 Tdi 170 will continue to run after I have turned the ignition off.  My understanding of this is that the engine is attempting a regeneration of the dpf filter (Please correct me if I am wrong).  Having returned from a 2500 mile round trip to the South of France I would have hoped that it may have gone some way to curing the problem.  For most of these miles the car has sat at 80 mph on the motorway.  However upon getting home and simply pottering around town when I turn off the engine the fan is once again continuing to run.  I have found that when it does this if I start the engine and then switch it off the fan will stay off.  In addition to this I observed on my return journey that the water temperature generally was below 90 degrees hovering around 80 degrees sometimes as low as 75. Could this be because the cooling fan is constantly on? On occasions it would get to 90 but wouldn't stay there.  Of all the VAG vehicles I have had the temperature needle is glued to 90 once it is warm, never budging.

Having borrowed a very basic diagnostic tool from a friend it indicated that an Exhaust Temperature Sensor may be at fault.  Does this sound about right?

 

Where do I go from here?  Are there any trustworthy Skoda/VAG engineers in the Peterborough area?

 

Any suggestions would be greatly appreciated.

PS. Current mileage is 160K

 

Is your car a DSG or manual?  Water temperature problem sounds very much like symptoms of a faulty DSG 'stat.  Very common problem although not one dealers tend to know about.  Search DSG thermostat for more info e.g. 

Unlikely to be anything to do with your fan issue, there is a known problem with fan relay sticking on and fan runs even when ignition is off but the ignition cycling switching fan off suggests not your problem.  The temperature sensor issue is a possibility as I assume this is what keeps fan running in an abortive DPF regen.  As chimaera suggests, full scan is next step to narrow down the problem

Thanks for your reply Corby. I do appreciate it. As Chimera suggest I’ll take the next step and get a full diagnosis. 
Cheers

Finally got round to purchasing a VCDS HEX-V2 and carried out a scan today.  Results as follows;

 

Address 01: Engine (J623-CFGB)       Labels:. 03L-906-018-CFF.clb
   Part No SW: 03L 906 018 CK    HW: 03L 906 018 BR
   Component: R4 2,0L EDC   X24 9823  
   Revision: 42X24---    Serial number:                CVN: 549C7B61
   Coding: 00190012042700080000
   Shop #: WSC 92521 052 00000
   ASAM Dataset: EV_ECM20TDI01103L906018CK 003006
   ROD: EV_ECM20TDI01103L906018CH.rod
   VCID: 75B7EC79254DC5F3C84-8020
   VINID: 91D49D5870E40532401812081C5A94A682

2 Faults Found:
5265 - Exhaust Gas Temperature Sensor; B1 S3 
          P242C 00 [040] - Short to Ground
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 119
                    Mileage: 248501 km
                    Date: 2022.05.06
                    Time: 06:23:51

                    Engine RPM: 1576.00 /min
                    Normed load value: 67.8 %
                    Vehicle speed: 51 km/h
                    Coolant temperature: 37 °C
                    Intake air temperature: 12 °C
                    Ambient air pressure: 1020 mbar
                    Voltage terminal 30: 14.220 V
                    Unlearning counter according OBD: 34
                    Exhaust gas temperature sensor 1: 378.0 °C
                    Exhaust gas temperature sensor 2: -0.0 °C
                    Exhaust gas temperature sensor 3: 900.0 °C
                    Exhaust gas temperature sensor 4: 65.4 °C
                    Shut-off timer: last engine shut-off time: 32802 s

5120 - Oxygen (Lambda) Sensor B1 S1 
          P2196 00 [096] - Signal too High (Rich)
          Intermittent - Not Confirmed - Tested Since Memory Clear
 

I'm reading this as an intermittent fault with sensor B1 S3. Having said that the readout shows sensor 2 as "-0.0". 

So my question is does anyone know if the fault is sensor 3 or is it sensor 2?  Depending on which one it is does anyone know how I go about finding a part number for the correct Temperature Sensor and where would it be located?

 

As before any help would be appreciated. 

Going by what you describe, it's likely to be both. That said, I'd have a good look at the wiring around there first. Three sensors in the same area with faults or spurious readings might be a damaged cable somewhere.

Thanks for your reply. Very much appreciated. 
 

I’ll investigate further. 

Thanks for your reply. Very much appreciated. 
 

I’ll investigate further. 

Had a look this afternoon and noticed that on one of the sensors (the one with the green marker tape on it in the image) there clearly is chafing on the lead with exposed copper. This most likely has been caused by the edge of the metal clip (top right of the image just passed the removable protective sleeve) that keeps the leads together. Do I now clear all fault codes and then rescan?  If no fault presents, can I just apply a suitable protective tape to the lead?  Do I just replace the sensor?  If so what is the part no.? Do I go used from well known auction website, go new genuine or new aftermarket alternative?

Try a repair, and then look with VCDS at live data when the car is running to see if the values in the fault code are now looking sensible.

 

This might give you more time to locate a part and replace.

Thanks. Are you suggesting just repairing the outer sleeping with a heat resistant tape. I’m assuming heat resistant rather than electrical insulation tape because of its location. 

*Sleeving not sleeping. 

Only as a bush fix or for diagnostic purposes.  It might be weak and break down quickly now, so best is a replacement if you can.

 

12 - Exhaust gas temperature transmitter 3 - G495-
❑ the thread of the temperature sender is coated
❑ do not apply additional oil or grease to the thread
❑ use spanner set 17 mm - T10395- for removing and installing
❑ 60 Nm

 

 

And what should be the part number you asked about (you should really double check this, but should be correct)

That will be your fault, one conductor was shorting to 0v via the clip.

 

Make sure it is well insulated and mechanically protected if you are going to put it back in the clip.

Thanks guys for your suggestions. I have temporarily carried out a repair using aluminium tape which is both corrosion and heat proof. Made thoroughly sure that it wouldn’t come in contact with the exposed copper of the sensors. Finally chose not to put back in the clip that caused the chafing. 
The constant trying to regenerate has stopped. Have rerun a scan and no codes coming up. I still have a suspicion that the thermostat is not working correctly as it struggles to get to working temp (90 degrees) and will drop back from 90 when idling. 
Is there a simple way of checking if the thermostat is working correctly either with or without using VCDS??

12 hours ago, Junips99 said:

Thanks guys for your suggestions. I have temporarily carried out a repair using aluminium tape which is both corrosion and heat proof. Made thoroughly sure that it wouldn’t come in contact with the exposed copper of the sensors. Finally chose not to put back in the clip that caused the chafing. 
The constant trying to regenerate has stopped. Have rerun a scan and no codes coming up. I still have a suspicion that the thermostat is not working correctly as it struggles to get to working temp (90 degrees) and will drop back from 90 when idling. 
Is there a simple way of checking if the thermostat is working correctly either with or without using VCDS??

Enable oil temperature display in the MFD, it well tell you the temperature of the engine more reliably than the temp gauge. 82-85 is normal under light loads, it'll probably hit 95 on a motorway cruise.

Thanks. I have a 35 mile run out later today mainly on single carriageway. I’ll observe the oil temp and report later. 

8 minutes ago, Junips99 said:

Thanks. I have a 35 mile run out later today mainly on single carriageway. I’ll observe the oil temp and report later. 

You may want to check the Soot measurements before/after your run to see if the values are in a nice range.

 

Just in case this broken sensor has stopped the regen process from happening correctly.

Thanks @chimaera &  @varooom Didn’t get chance to run a scan before leaving. 
The findings of my run this afternoon are as follows;  

 

38 miles each way. Maximum speed 70mph for approx 5 miles. Typically 55mph. Numerous roundabouts enroute. 

 

Outward journey, ambient temp 6.5C. Maximum oil temperature 81C.  Sat mostly around 78C. Water temperature only reached 90C once (after dual carriageway when slowing down), sat around 80c most of the time. 

Return journey, ambient temp 5C. Maximum oil temperature 80C.  Sat mostly around 77/78C. Max water temperature 85C , sat around 80c most of the time. 
 

My conclusion is the thermostat is stuck open. Whilst driving the airflow through the radiator is cooling due to speed of the car. Greater speed = more cooling hence a rise in temp when slowing down for roundabout etc. 

 

If correct is changing the thermostat a DIY job or a trip to the mechanic??  Engine type CFBG. 

Not too sure if this is the best place to post but here we go.

 

I still have a problem where the car will not get to a coolant operating temp of 90 degrees.  I took it out for a 12 min drive this evening outside temp 5 degrees C.  Before I left oil temp was 77.5, coolant temp was 75.0.  During the drive the coolant varied between 76 & 68.  The Coolant temp at radiator outlet - actual varied between 68.7 & 76.6.  Oil temp varied between 77.5 & 82.6.  The highest coolant temps were when I was idling and the lowest when travelling the fastest.  When I was idling the temp gauge rose to nearly 90 whilst during driving it sat at around 75-80.

 

Something to also note is that the "Coolant temperature at radiator outlet ; specified" is set at 80.  Is this correct?  

 

Any observations would be appreciated.

 

Thanks 

1 hour ago, Junips99 said:

Not too sure if this is the best place to post but here we go.

 

I still have a problem where the car will not get to a coolant operating temp of 90 degrees.  I took it out for a 12 min drive this evening outside temp 5 degrees C.  Before I left oil temp was 77.5, coolant temp was 75.0.  During the drive the coolant varied between 76 & 68.  The Coolant temp at radiator outlet - actual varied between 68.7 & 76.6.  Oil temp varied between 77.5 & 82.6.  The highest coolant temps were when I was idling and the lowest when travelling the fastest.  When I was idling the temp gauge rose to nearly 90 whilst during driving it sat at around 75-80.

 

Something to also note is that the "Coolant temperature at radiator outlet ; specified" is set at 80.  Is this correct?  

 

Any observations would be appreciated.

 

Thanks 

To me this still sounds like the DSG thermostat.  Can't find confirmation in the thread whether yours is DSG or manual or whether you changed the DSG thermostat.  Certainly that's the cheapest and easiest fix to try first if it is a DSG.  With mine, dealer was adamant the problem was the main thermostat despite me telling them it had to be the DSG one (thanks to this forum 😉 And sure enough, changing main one didn't cure the problem but DSG one did.  I didn't mind them using the 'parts cannon' to diagnose the problem as it was an extended warranty claim, although funnily enough the actual DSG thermostat itself wasn't covered. I was more that happy to pick up the 30 quid tab for that with all the labour covered by warranty which was 4 or 5 hours total for changing the two stats and, I suspect, a lot of time stood scratching their heads trying to diagnose the problem even though I'd already told them the answer! I really should have back-charged them for my diagnostic time 🙂

9 minutes ago, DrCorbyLee said:

Can't find confirmation in the thread whether yours is DSG or manual or whether you changed the DSG thermostat. 

You must be on a phone or tablet (like I usually am)

 

In desktop mode...

4x4 170 Tdi Manual 

 

I guess the thermostat has failed stuck open by the sounds of the symptoms?

Edited 3 January, 20233 yr by varooom

7 hours ago, varooom said:

You must be on a phone or tablet (like I usually am)

 

In desktop mode...

4x4 170 Tdi Manual 

 

I guess the thermostat has failed stuck open by the sounds of the symptoms?

Yep, on mobile, damn technology 🙂

 

Didn't even know they did a manual 4x4 170, when I got my facelift car only option for the 170 4x4's was DSG. Must be a pre-FL car?

 

@Junips99 - Symptoms do sound very much like main thermostat stuck open giving uncontrolled flow of coolant through rad' which gets cooled more by airflow at high speed, hence faster = colder. Can't unfortunately help with any advice re practicalities or cost of thermostat swap. Maybe invest a few quid to access ERWIN system for an hour and download all the workshop manuals etc for your car which should hopefully provide step by step instructions.

Thanks @DrCorbyLee.

 

Have purchased a days access to ERWIN.  Do you know if there is a parts listing anywhere on the system?  looking to download as much as possible.