P0546 Exhaust Gas Temperature Sensor Circuit High (Bank 1)

[nick.king]

Afternoon all,

Experienced a fault on my way to work this morning, started with a brief ping then the glow plug light flashing and a engine fault workshop message, it was on for a few seconds then appeared to clear. This happened 5 or 6 times over the next 30 seconds or so, it then cleared for about a mile and then started again. I was only 3 miles from work when first occurred and I didn't experience any loss of power or any other symptoms.

When I got to work I turned off the engine and restarted it a few minutes later, at this point the engine light also illuminated and stayed illuminated.



I managed to get it scanned at lunch and it returned P0546 Exhaust Gas Temperature Sensor Circuit High (Bank 1), we cleared the code but it immediately returned when I started the engine.

VRM AO57SDU VW Passat 2.0 BMR 170 TDI Sport (178k miles)

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First question, will it be OK to drive the 15 miles back home (either motorway or through the city centre)?

Second question, what exactly does the fault mean and what should I be checking first? I have access to technical data at work at it shows 3 possibly locations, I'm not sure which is which also which part would need replacing/cleaning.

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I've had a search on the site but not found this particular fault.

Any help or advice appreciated.

Thanks,

Nick.

[DMitch16]

This fault is relevant to the first DPF temperature sensor - there are 2 on a B6 BMR engine, one 'pre turbo' which is actually inside the exhaust manifold section measuring the exhaust gas temperature exiting the turbo and the other on the exit pipe from the DPF can measuring the exit temperature of exhaust from the DPF. The ECU needs these inputs to determine whether it should passively regenerate soot collecting in the DPF as you drive or whether to instigate an active regeneration based on soot load presently accumulated in the DPF can filter. If temperatures fore and aft of the can, along with a few other monitored conditions, are high enough during normal driving (usually motorway or faster roads), the soot is burned slowly into ash and the minute ash particles stored in the DPF can filter. The filter gradually fills up until it needs cleaning or replacement usually around 100 to 150k but this can happen earlier or much later depending on how the car is used. Longer sustained journeys where revs are above 2000 will cause more efficient passive burning of the soot whereas short town journeys will most likely lead to a periodic active burn, less fuel economy and less combustion efficiency.

Best scenario - you now have a dirty EGT sensor, which can be cleaned carefully but there are precious metals inside the cage end so no wet cleaners just remove any deposits from the outer shell and carefully blow any deposits out of the cage. A bit worse - the sensor wiring or sensor itself is damaged meaning if no fix possible, a new sensor at around £115. This usually means your glow plug preheat light will be flashing or permanently on with the EML light signifying that your emissions are worse as it is an emissions warning light not a traditional EML general engine fault warning (that's actually the flashing coil).

There is a worst case scenario and not wanting to scare you at this point but you should know - That such sensor failure precedes head failure as many BMR engines suffer from cracks in the head between cylinders. Some carry on regardless as the cracks may be within VW anticipated tolerances (yes, VW knew about such issues for many years and if the cracks stay small the engine is considered fine). When the cracks expand however to a point where gases, coolant or oil is commuted from one system to the other or into the cylinder itself...time for a new head. Keep an eye on your coolant level as it is a good indicator of whether something like the above is going on as coolant often seeps from the head water jacket into the cylinders and the steam knocks out the EGT sensors. Mine popped 3 sensors in 12 months and I then knew I had the porous head issue.

Good luck - I hope it is a minor issue.

[Kyle_471]

This fault is relevant to the first DPF temperature sensor - there are 2 on a B6 BMR engine, one 'pre turbo' which is actually inside the exhaust manifold section measuring the exhaust gas temperature exiting the turbo and the other on the exit pipe from the DPF can measuring the exit temperature of exhaust from the DPF. The ECU needs these inputs to determine whether it should passively regenerate soot collecting in the DPF as you drive or whether to instigate an active regeneration based on soot load presently accumulated in the DPF can filter. If temperatures fore and aft of the can, along with a few other monitored conditions, are high enough during normal driving (usually motorway or faster roads), the soot is burned slowly into ash and the minute ash particles stored in the DPF can filter. The filter gradually fills up until it needs cleaning or replacement usually around 100 to 150k but this can happen earlier or much later depending on how the car is used. Longer sustained journeys where revs are above 2000 will cause more efficient passive burning of the soot whereas short town journeys will most likely lead to a periodic active burn, less fuel economy and less combustion efficiency.

Best scenario - you now have a dirty EGT sensor, which can be cleaned carefully but there are precious metals inside the cage end so no wet cleaners just remove any deposits from the outer shell and carefully blow any deposits out of the cage. A bit worse - the sensor wiring or sensor itself is damaged meaning if no fix possible, a new sensor at around £115. This usually means your glow plug preheat light will be flashing or permanently on with the EML light signifying that your emissions are worse as it is an emissions warning light not a traditional EML general engine fault warning (that's actually the flashing coil).

There is a worst case scenario and not wanting to scare you at this point but you should know - That such sensor failure precedes head failure as many BMR engines suffer from cracks in the head between cylinders. Some carry on regardless as the cracks may be within VW anticipated tolerances (yes, VW knew about such issues for many years and if the cracks stay small the engine is considered fine). When the cracks expand however to a point where gases, coolant or oil is commuted from one system to the other or into the cylinder itself...time for a new head. Keep an eye on your coolant level as it is a good indicator of whether something like the above is going on as coolant often seeps from the head water jacket into the cylinders and the steam knocks out the EGT sensors. Mine popped 3 sensors in 12 months and I then knew I had the porous head issue.

Good luck - I hope it is a minor issue.

Mitch I don't suppose you know the thread size of the post dpf sensor do you? I messed up when taking my dpf off to remove my broken turbo and broke the sensor mentioned. When trying to remove it the sensor is seized and we're going to have to try get it out then tap it to fit the new one.
That or weld on a new bit of pipe and tap that for the new sensor but again need the thread size to do it.

Cheers

[DMitch16]

M14 x 1.5 if I recall.

[nick.king]

Thank you Mitch for the response, you don't happen to know any part numbers do you so I can have a look around for parts?

Many thanks,

Nick.

[DMitch16]

03L906088N is the EGT sensor in the manifold - it is a total PITA to reach as you have to go in from below in the gap between subframe and engine. 17mm crows foot needed and it is awkward to do up to a sufficient tightness. The sensor has an angled neck which must be positioned correctly as far away from each of the hot surfaces so basically angled out between the two concerned.

[Kyle_471]

Afternoon Mitch,
My part number is 03g906088b, there are loads of different part numbers that appear the same to mine however mines not angled as you mentioned. Would a 03l906088k or 03l906088be fit on mine as I've found one local.
Sorry hijack your thread nick.

[Crasher]

There are three temp senders on the BMR, Sender 1 G235 in the exhaust manifold before the turbo 03L 906 088 AN which changed to 03G 906 088 AT and is now 03L 906 088 BS, sender 2 G448 in the top of the particulate filter 03G 906 088 and sender 3 G527 after the DPF 03G 906 088 B which changed to 03L 906 088 CE and now is 03L 906 088 HM.

03L 906 088 N changed to 03L 906 088 AJ and is now 03L 906 088 J and is for Common Rail injection EU5 engines in the Golf, A3 etc with engines codes such as CBEA and CJAA.

[DMitch16]

Afternoon Mitch,
My part number is 03g906088b, there are loads of different part numbers that appear the same to mine however mines not angled as you mentioned. Would a 03l906088k or 03l906088be fit on mine as I've found one local.
Sorry hijack your thread nick.

Ah yours is a BKP if I recall is it not?

[Kyle_471]

Mines BMR mate.