DPF Pressure Sensors Melted

bigb

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Have not seen that. What kind of driving patterns, mostly short? How many miles on it and do you monitor your regens?
 

Lightflyer1

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Not under warranty? If I was I would try and have them fix everything first then delete if you choose to. Why foot the bill for that stuff? You don't know what all is affected there really. There may be other burned up stuff in that mess.
 

cpinde

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Have not seen that. What kind of driving patterns, mostly short? How many miles on it and do you monitor your regens?
Just shy of 180k miles. Almost all driving is from my commute which is 126 miles each way. My driving would be considered spirited with most drives my car sees 100mph runs. I don't monitor regens but rarely do my regens get interrupted.
 

cpinde

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Not under warranty? If I was I would try and have them fix everything first then delete if you choose to. Why foot the bill for that stuff? You don't know what all is affected there really. There may be other burned up stuff in that mess.

Technically not under warranty but I'm thinking about taking it to VW and trying to get VW to cover it. Sadly I live about 40 miles from the dealership so I'll have to tow it there, good thing I have a truck and a tow dolly.
 

740GLE

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You sure you don't have a massive exhaust leak at the DPF?
Those pressure sensors are for the exhaust, under normal operation there's no flow as its capped, so no soot, but soon as one end is opened you'll have flow. My guess when the melted, some soot shot past and filled up the heat shield.
 

ticaf

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Those pressure sensors are for the exhaust, under normal operation there's no flow as its capped, so no soot, but soon as one end is opened you'll have flow. My guess when the melted, some soot shot past and filled up the heat shield.
I think you are right. The pressure sensor cracked and allow soot through.
Wondering if the failure is due to overpressure caused by a full DPF.
To the OP, what are the codes?
 

740GLE

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I've replaced a failed sensor on my 2010 and it failed signal/electrical wise not port/fitting wise, soon as there is a little crack in that sensor and flow of exhaust gasses happen she'll melt quite quickly.

So it's prob chicken or the egg, did a regen get a bit hot under the collar and melted it or was there a micro crack that finally failed.

How long did the OP drive after a CEL happen?
 

amontobin

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This happened to my '15 MK7 MT Wagen after a t-belt change. It was running fine in town but the first time out on the highway (presumably first re-gen) it went into limp mode. I limped to my errand, then had a CEL on the drive home. Code read DPF Sensor Fail. Sure enough- melted sensor.

It's apparently a thing that can happen sometimes after a t-belt change?
 

Brian's96TDIPASSAT

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This happened to my '15 MK7 MT Wagen after a t-belt change. It was running fine in town but the first time out on the highway (presumably first re-gen) it went into limp mode. I limped to my errand, then had a CEL on the drive home. Code read DPF Sensor Fail. Sure enough- melted sensor.

It's apparently a thing that can happen sometimes after a t-belt change?
Just happened last week on my 15 Golf after I changed the t-belt and pump. First re-gen about 80 miles later and it smoked it. Got parts/harness repair under VW emission warranty extension so it only cost me a few hours at the dealer
 

ticaf

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Makes sense, cracked during timing belt change from moving them around. I assume it was already brittle
 

Brian's96TDIPASSAT

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Makes sense, cracked during timing belt change from moving them around. I assume it was already brittle
Never moved them around enough to crack anything. Trust me, just removed the one bolt securing the bracket that holds the assembly. Most of any moving around is not in that area.
 

740GLE

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were you able to just replace the sensor? or the plumbing for the sensor to fix the issue?
 

RIP TDI

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If the sensor is that fragile after all those heat cycles, it might make sense to proactively replace it during a TB change. that would at least save having to also replace the harness and it would be one less thing for the dealer to touch.
 

Brian's96TDIPASSAT

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were you able to just replace the sensor? or the plumbing for the sensor to fix the issue?
It was fixed by the dealer under the extended policy. The sensor came with both sensors, mount, cover and hoses along with a repair harness that was spliced in.
 

Brian's96TDIPASSAT

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If the sensor is that fragile after all those heat cycles, it might make sense to proactively replace it during a TB change. that would at least save having to also replace the harness and it would be one less thing for the dealer to touch.
Trying to figure out why it happened. I really don't think it's anything to do with the belt change in regards to the actual physical replacement of the belt. Has to be something with having the battery cables off for a day along with possible changes from a stretched belt to a new belt.
 

740GLE

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a crack/slice in hosing/connections must have happened to allow flow of exhaust gasses through the sensor
 

pedroYUL

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We are talking about what's inside the metallized pouch here, right?
 

pedroYUL

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If yes. That doesn't need disconnecting while a timing belt change, the DEF injector yes like this:
 

hskrdu

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The owners in the thread linked by amontobin above from the BRISKODA forum (almost) all report the sensor melting after a TB change, with at least a few confirmations that the mech did not touch the area. Coincidence? Possible....
 

pedroYUL

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Great! Another thing to check and be paranoid about it 🙄 I'll open that pouch later today

Edit: checked and it's all good.
 
Last edited:

740GLE

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my guess is that some shops disconnect the hard pipes the cross the def injector/TB shown in your second picture for ease of access and they don't get seated 100% afterwards.
 

Brian's96TDIPASSAT

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my guess is that some shops disconnect the hard pipes the cross the def injector/TB shown in your second picture for ease of access and they don't get seated 100% afterwards.
Well I can assure you I did not remove hard pipes, hoses or connectors. You simply have to remove the bolts for hard pipe attached to the upper timing cover.
 

740GLE

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You push the pipes away while doing the timing belt?

Sounds like if you look at those sensors/piping wrong you maybe set up for failure.
 

demagxc

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Great! Another thing to check and be paranoid about it 🙄 I'll open that pouch later today

Edit: checked and it's all good.
No need to periodically check the sensors. When they go, they go, and you'll know it. Failure triggers a check engine light and when the sensor melts down, the cabin smells like melted plastic and you may see smoke coming from under the hood. At least this was my experience.
 

pedroYUL

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No need to periodically check the sensors. When they go, they go, and you'll know it. Failure triggers a check engine light and when the sensor melts down, the cabin smells like melted plastic and you may see smoke coming from under the hood. At least this was my experience.
Should they be in a replace schedule (TB schedule sounds reasonable)? I hate to have to splice connectors and such.
 

pedroYUL

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Just finished the timing belt work in my 2015 Passat (CVCA engine), and indeed the plumbing is routed differently than in CRUA. I can see how if you are not gentle here, you could damage one of those sensors.

I had to release both sensors from the bracket, and the one closer to the driver-side I actually had to unplug the hose...both needed to be electrically unplugged too:
 

pedroYUL

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Did my wife's CRUA timing belt last April, and honestly don't recall having to undo those sensors, I never open that pouch... hasn't melted anything yet.

I am 90% sure I cut short a regen right before doing my Passat CVCA timing belt...actually, when I test drove my car right after, the engine stayed at around 1k rpm and later I realized it was finishing that regen interruptus... didn't melt anything...yet.

I'll report here if something does happen.
 
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