Weird T6 Problems - Solved

[ebiii]

Hello everyone, I have a small question and I hope someone can help me. So brace yourselves, I have quite a story below I have a 2016 T6 4motion 2.0 TDI with a CXFA 150hp engine and 50,000 km mileage. History:

• A cable gnawed by a marten, hence a repair and installation of a marten deterrent system.
• From time to time, the glow plug light turns on while driving but it's very rare.

For the past 2 months my problems have worsened:

• Sometimes (every other time) there's a loss of power during the first 30 seconds (can't start uphill without aggressively accelerating, etc.)
• I have a sense of consuming more fuel and having generally less power, but it's not too obvious.
• Sometimes there's strong ventilation under the hood when the car is stopped and shut off, and sometimes not (regardless of engine temperature).
• Occasionally, the glow plug light starts flashing after taking the highway with a strong power limitation around 100 km/h.
• The engine light is constantly orange.

I did an initial diagnostic with OBDEleven:

P010100 - Mass or Volume Air Flow Sensor "A" Circuit Range/Performance
Intermittent
P24D000 - Particulate Matter Sensor Supply Voltage Circuit Low
Intermittent
P046C00 - EGR Sensor "A" Circuit Range/Performance
Intermittent
P040200 - Exhaust Gas Recirc.Flow Excessive Detected
static
P066A00 - Cylinder 1 Glow Plug Control Circuit Low
Intermittent
P066E00 - Cylinder 3 Glow Plug Control Circuit Low
Intermittent
P019100 - Fuel Rail Pressure Sensor "A" Circuit Range/Performance
Intermittent
P056200 - System Voltage Low Voltage
Intermittent
P064100 - Sensor Reference Voltage "A" Circuit Open
Intermittent
P065100 - Sensor Reference Voltage "B" Circuit Open
Intermittent
P069700 - Sensor Reference Voltage "C" Circuit Open
Intermittent
P06A300 - Sensor Reference Voltage "D" Circuit/Open
Intermittent

I reset it, and did another diagnostic a few weeks later without having driven, and the codes are almost completely different:
P226D00 - Particle filter damaged or substrate missing Intermittently

P24B100 - Particle sensor measurement electrode short-circuit to positive pole Intermittently

P24B000 - Particle sensor measurement electrode short-circuit to ground Intermittently

P046C00 - Exhaust gas recirculation transmitter 1 implausible signal Intermittently

P040200 - Exhaust gas recirculation system excessive flow Static

P029900 - Boost pressure regulation limit not reached Intermittently


I note that the codes P046C and P0402 related to EGR and exhaust are the only ones that repeat.

In conclusion, I think it's a problem with cables that have been gnawed or oxidized connectors, but I don't see anything under the hood (I didn't go under the car and I didn't disassemble anything).

My questions are as follows:

• Do you have any idea where this could be coming from?
• What are the components I should check?

A big thank you in advance and kudos to those brave souls who read through everything

 

[mmi]

Sometimes there's strong ventilation under the hood when the car is stopped and shut off, and sometimes not (regardless of engine temperature).

Most likely DPF regeneration was still going on when engine was shut off. Then engine controller runs radiator fan at high speed. Perfectly normal.

I did an initial diagnostic with OBDEleven:

I would ignore all the intermittent ones for now - from the initial scan -as we don't have any date stamps.

P226D00 - Particle filter damaged or substrate missing Intermittently

P24B100 - Particle sensor measurement electrode short-circuit to positive pole Intermittently

P24B000 - Particle sensor measurement electrode short-circuit to ground Intermittently

Please check exhaust tailpipe - is it sooty?
Short circuits suggest to verify it's not a wiring problem.

P046C00 - Exhaust gas recirculation transmitter 1 implausible signal Intermittently

P040200 - Exhaust gas recirculation system excessive flow Static

I would start by running engines internal EGR cooler diagnostics test as described here:

[T6_measured] 01-Engine - Built-in test for EGR

So it seems - inevitable P0401. Well, visited a VW garage to be tested - the van had accumulated 30 events in ECU's memory since July 2021 (since 20 months now). Eventually managed turn on the emission light at event number 31 - thus had a priviledge to have EGR flow tested. The result -...

www.t6forum.com

Note: OBDeleven can initiate the test but I'm not sure if it can capture the relevant data at useful rate.

P029900 - Boost pressure regulation limit not reached Intermittently

I would check for air leaks - cracks, loose joints from turbo to charge air cooler to intake manifold.

Occasionally, the glow plug light starts flashing after taking the highway with a strong power limitation around 100 km/h.

Most likely triggered by P029900

The engine light is constantly orange.

Most likely triggered by P040200

 

[ebiii]

Most likely DPF regeneration was still going on when engine was shut off. Then engine controller runs radiator fan at high speed. Perfectly normal.


I would ignore all the intermittent ones for now - from the initial scan -as we don't have any date stamps.



Please check exhaust tailpipe - is it sooty?
Short circuits suggest to verify it's not a wiring problem.



I would start by running engines internal EGR cooler diagnostics test as described here:

[T6_measured] 01-Engine - Built-in test for EGR

So it seems - inevitable P0401. Well, visited a VW garage to be tested - the van had accumulated 30 events in ECU's memory since July 2021 (since 20 months now). Eventually managed turn on the emission light at event number 31 - thus had a priviledge to have EGR flow tested. The result -...

www.t6forum.com

Note: OBDeleven can initiate the test but I'm not sure if it can capture the relevant data at useful rate.



I would check for air leaks - cracks, loose joints from turbo to charge air cooler to intake manifold.



Most likely triggered by P029900


Most likely triggered by P040200

Many thanks for the time you've taken to answer point by point. I will do everything you suggested and keep the thread updated

 

[ebiii]

Most likely DPF regeneration was still going on when engine was shut off. Then engine controller runs radiator fan at high speed. Perfectly normal.


I would ignore all the intermittent ones for now - from the initial scan -as we don't have any date stamps.



Please check exhaust tailpipe - is it sooty?
Short circuits suggest to verify it's not a wiring problem.



I would start by running engines internal EGR cooler diagnostics test as described here:

[T6_measured] 01-Engine - Built-in test for EGR

So it seems - inevitable P0401. Well, visited a VW garage to be tested - the van had accumulated 30 events in ECU's memory since July 2021 (since 20 months now). Eventually managed turn on the emission light at event number 31 - thus had a priviledge to have EGR flow tested. The result -...

www.t6forum.com

Note: OBDeleven can initiate the test but I'm not sure if it can capture the relevant data at useful rate.



I would check for air leaks - cracks, loose joints from turbo to charge air cooler to intake manifold.



Most likely triggered by P029900


Most likely triggered by P040200

So I did the following checks :
- Pipe soot : seems so, see pictures below:
- Egr output cooler test : can't seem to make it work with obd11
- I checked the cables saw nothing except a repair of a previously bitten cable, maybe not well repaired ? I don't understand what the cable does
- I also noticed a strange ventilation noise outside on the left near the fuel reservoir

Anyways I dont think I'll be able to repair it myself, took an appointment at the garage on May 30th

 

[mmi]

- Pipe soot : seems so, see pictures below:

Not a good sign - there should be no soot.
See how clean it should be in pictures in the link

Engine codes and DPF.

Thank you Guys ones again for support. @mmi According to pressure on DPF, do I correctly understand if there is low pressure different, then DPF is working like a "stright pipe"? What I notice during burning DPF, the RPM's growth up to 1000 but fuel consumption is still at the same level. In...

www.t6forum.com

The sooty exhaust would explain the code

P226D00 - Particle filter damaged or substrate missing Intermittently​

Looks like you found (likely) cause for

P029900 - Boost pressure regulation limit not reached​

​

I checked the cables saw nothing except a repair of a previously bitten cable, maybe not well repaired ? I don't understand what the cable does

Did you check the cable from/to particulate sensor?

The operation of the particulate sensor can be monitored by OBDeleven - I'm curious to see the following read-outs - especially the surface temperature - please keep eye on it for a few minutes (ignition on, engine off)

Control Units > Engine > Live Data >

​

 

[ebiii]

Not a good sign - there should be no soot.
See how clean it should be in pictures in the link

Engine codes and DPF.

Thank you Guys ones again for support. @mmi According to pressure on DPF, do I correctly understand if there is low pressure different, then DPF is working like a "stright pipe"? What I notice during burning DPF, the RPM's growth up to 1000 but fuel consumption is still at the same level. In...

www.t6forum.com

The sooty exhaust would explain the code

P226D00 - Particle filter damaged or substrate missing Intermittently​

Looks like you found (likely) cause for

P029900 - Boost pressure regulation limit not reached​

​

Did you check the cable from/to particulate sensor?

The operation of the particulate sensor can be monitored by OBDeleven - I'm curious to see the following read-outs - especially the surface temperature - please keep eye on it for a few minutes (ignition on, engine off)

Control Units > Engine > Live Data >

​

View attachment 199272​

Thanks for the tips.

I did measure it for a few minutes with ignition ON. From the very start to finish I had these measurements attached

 

[mmi]

Ok. Thanks. It seems that the sensor gives plausible values - and, yes 200 C is what is seen when engine off.

The values Cleaning deviation, Time in op. mode and Heat quantity for dewpoint normally activate after approx. 15 minutes driving - for short periods every now and then

I believe the Measuring current calculated activity would indicate soot particles detected in exhaust stream. Normally it stays at "0".

 

[ebiii]

Ok. Thanks. It seems that the sensor gives plausible values - and, yes 200 C is what is seen when engine off.

The values Cleaning deviation, Time in op. mode and Heat quantity for dewpoint normally activate after approx. 15 minutes driving - for short periods every now and then

I believe the Measuring current calculated activity would indicate soot particles detected in exhaust stream. Normally it stays at "0".

It seems to be verified, just drove about 15 minutes and got the following values (attached)

 

[ebiii]

Went to the garage, apparently it's the EGR valve that is dead :/ Close to 1000 gbp to change it, so I'll do it and check if all my problem disappear (I hope so)

 

[ebiii]

Got the appointment on Monday 12th. I think I'll also make a professional lean the Particulate Filter and make an engine flush ? I imagine soot and carbon can be in excess everywhere when having a faulting EGR for months no ? What do you think ?

 

[ebiii]

well it seems that it solved the problem, it cost about 1200 gbp :/

 

[ebiii]

Well that's not over... got engine light, code P226D, DPF Deteriorated/Missing Substrate Bank1

 

[Phil_j89]

Substrate fault and soot in the DPF will always be a dead DPF.

 

[ebiii]

Substrate fault and soot in the DPF will always be a dead DPF.

It's really suprising at 50 000 kms no ? is there any chance a faulty sensor lead to that ?
I think sensors work, except maybe for the 'dpf differential pressure raw value 2' where I have a doubt. I don't know if it's supposed to be different from 0 here

 

[ebiii]

Well last update :
The garage forgot to change the joint on the EGR Valve, causing a small leak, might be the problem, we'll see beginning of July

 

[Phil_j89]

Won’t be the problem.

Substrate fault, and soot at the tailpipe means the dpf has failed. It doesn’t happen because of a sensor issue.

A sensor fault may have caused the dpf to fail, but a sensor issue isn’t the reason you have soot on the tailpipe.

 

[ebiii]

I think the previous owner did put a weird oil, I have no idea which one but apparently it can cause these kind of problems

 

[ebiii]

To close the problem, the source of everything was a faulty fuel rail pressure sensor...

 

[Phil_j89]

Did you get the dpf replaced?

Fuel pressure sensor won’t cause spot in the exhaust.

 

[ebiii]

Did you get the dpf replaced?

Fuel pressure sensor won’t cause spot in the exhaust.

No it hasnt been replaced.

I think that because of the faults sensor the air/fuel mixture was too rich, causing constant soot. I dont see any other reason