Okay to drive with Reductant Pressure too Low CEL?

[dukelukas]

Hello internet TDI friends - hoping to get some of your knowledge.

Yes, I'm doing some searching but also hoping for a quick answer since I had a camping trip planned for this afternoon with the vehicle...

It's a 2016 Touareg TDI engine code CNRB.

Yesterday I started getting a CEL, plugged in the VAG Com and I'm reading a Reductant Pressure too low fault. Full code details below.

Question: Is it okay to drive (long distances, and hauling a trailer) with this fault? I read somewhere that the DEF is injected above the DPF and is necessary for correct functioning of the DPF. I read somewhere else that they are completely unrelated.

I see a thread about Adblue delete, which I will read, but makes me think it's okay to drive without adblue being injected ....???

Thanks!


1 Fault Found:

9645 - Reductant
P20E8 00 [237] - Pressure too Low
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 142780 km
Date: 2021.09.16
Time: 16:43:01

Engine RPM: 1743.50 /min
Normed load value: 85.5 %
Vehicle speed: 73 km/h
Coolant temperature: 88 °C
Intake air temperature: 38 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 14.360 V
Unlearning counter according OBD: 40
Outside temperature: 24.0 °C
Pressure sensor for reducing agent: measured pressure: 0 hPa
Mean temperature of SCR catalyst: 184.4 °C
Sensor for reducing agent tank temperature: temperature: 27.6 °C
Reducing agent pump: activation: 80.00 %
Reducing agent injector: activation: 0.00 %


Readiness: 1 1 0 0 0

 

[oilhammer]

SCR and DPF are two different things.

It will eventually go into some form of limp or reduced power mode.

No idea how long that will take, but eventually if the DEF dosing is not right, it will.

DEF gets injected AFTER the DPF, and has nothing to do with that. There are diesels that have a DPF and no SCR, and there are diesels that have no DPF and have SCR.

DPF is to reduce particulates, SCR is to reduce NOx. Or, more accurately, convert NOx back into Nitrogen and Oxygen in a chamber post DEF injector in which that reaction takes place, before it leaves the tailpipe. Otherwise, it *can* create smog in sunlight in high concentrations but will normally separate out on its own in the atmosphere within a few days or weeks.

 

[dukelukas]

Thanks for the fast reply oilhammer... what if I keep clearing the code?

Will it do mechanical harm? It sounds like the answer is no.

 

[oilhammer]

I cannot see it doing any mechanical harm, no. I would assume if you can clear the DTC, and it takes a while for it to come back (not right away, like a hard fault), you could conceivably drive it a long distance like that.

 

[TurboABA]

Umh.... I could be missing something, but you're going long distance, pulling a TT (read it will want to dose even more than normal)......
So all you're doing is asking to end up needing to get both your TW & TT (and probably a bunch of family) towed back from far away (read not cheap).

I can't imagine that you'll want to clear the codes 100 times if it starts going to limp or reduced power non stop just to get home.
You should be able to pull the dosing injector out and clean it if you don't have the fix warranty on it still, but with a '16, I'd be shocked if you've already exhausted that.

Cancel your camping trip and take it to the dealer for a no cost repair.... or rent another TW if you're really set on going camping.... or talk to the dealer to see if they will give you a loaner capable of towing your TT.....

That's all I've got.

 

[mannytranny]

Low pressure sounds like a faulty pump, so cleaning the injector probably won't do anything?

You'll soon get a warning screen '200 miles to no start.' No kidding. If you have Vagcom you can continue to reset the lockout, but I think each time you do it you'll only have '50 miles to no start.' So doing that every 50 miles may become tiresome. I drove 2000 miles doing this (long trip, no dealers that I wanted to waste my vacation at) and never had a limp mode of any sort. Luckily mine showed a low consumption code and I was able to clean the injector. Only driven 350 miles since doing this so still unsure whether or not it fixed it. Delete will be forth coming.

 

[dukelukas]

So here's the update:
- I cleared the CEL with my VAG Com 2-3 times, then it stopped coming back on. I.e., the CEL has been off for days.
- I have verified with VAG Com that the reductant pressure continues to be zero, and it's injecting 0% while driving around.
- No limp mode
- However, we did start to get the dreaded software interlock "Car won't start in 600 miles"
- Cancelled the camping trip, parked the TT in the yard, didn't go in the house, and had a blast
- Yes, the emissions system has lifetime warranty as part of the recall.
- Soonest dealer can do "regularly scheduled" service is November 18th (yes, two months out)
- We called today to ask what we can do if the car won't start. They said we can have it towed there for an "emergency service" when they can take a look at the car "right away" in 2-3 weeks. There isn't an emoji for how that makes me feel.

This is why I learned to work on cars myself. Hey @mannytranny, how do I reset the start lockout with VagCom? I couldn't figure it out the other day.

As for actual fix, I'm guessing it's either the pump or the pressure sensor, but I can't find much info on what it takes to replace either/both of those. If I have to, I will. This is my wife's haul-the-kids-around car as well as our tow vehicle. It can't be down for 2 months.

 

[mannytranny]

I can't recall exactly how it is reset but I think it is in basic settings. The best info I found on this was in the VagCom forums - lots of helpful stuff in there RE Ad Blue problems.

AdBlue countdown to doom

Hello all, new VCDS owner here. I have the "Check AdBlue, no engine start in 450 miles" message on my Alhambra 7N. The story so far: -I've had car about 6 months. In the first week of ownership the same happened and it went to dealer for software updates and came back happy and clear of that...

forums.ross-tech.com

 

[TurboABA]

@dukelukas you may wish to try this until you can get it in to get "fixed"

 

[dukelukas]

Thank you both for the links. My VagCom doesn't give me the "Long Adaptation" option, so I don't see the "AdBlue SCR Reset" -- I'll have to try the Basic Settings route.

**BUT, now my saga continues with the issue having "fixed itself" - yesterday everything is back to normal, with the reductant pressure, activation, and all other indicators returning to normal. This makes me suspect a loose/faulty connection to the pressure sensor. I'll have to investigate.

 

[dukelukas]

So my problem is back and the count down is down to 85 miles.

If anybody knows how to reset the counter for vehicles that don't support the "Long Adaptation" option, some help would be awesome! I've also posted that question on the Ross-Tech forum....

 

[TurboABA]

Did you try reading the MVB shown in the video?
Pulling the fuse mentioned?

When you say your vehicle doesn't support "long adaptation"..... is that a cable interface limitation or what?

 

[TurboABA]

You should still be under warranty... both powertrain and dieselgate.... I'd drive it into the dealer and ask them to reset it so you can continue driving it until they can schedule you in for service, or drive off in the loaner vehicle that they would owe you otherwise.

 

[dukelukas]

That's a good idea... I'll try calling the dealer and see if they will do that. When we asked them before what they would do if we get down to the car not starting, they said we could have it towed there but it would still be two weeks before they could look at it. So I'm not hopeful.

You should still be under warranty... both powertrain and dieselgate.... I'd drive it into the dealer and ask them to reset it so you can continue driving it until they can schedule you in for service, or drive off in the loaner vehicle that they would owe you otherwise.

 

[showdown 42]

I hope these types of things we will be seeing more of after the cars have been "fixed"to consume more ad blue. Not happy with the thought. I've had a 1000 mi ad blue alert way before it was suppose to come on a long trip this fall. Super pain to deal with on the road with a full load in the hatch compartment.

 

[TurboABA]

I don't know why everyone is crying about this so much. If you've owned the fixed vehicle for any amount of time, you should have a decent idea of what your typical usage pattern is like and of what type of DEF consumption rate is to be expected. That alone allows you to "plan" accordingly. If you have a significant tow/trip coming up, top up your tank before you pack.

I remember early in my ownership stage, all the fear mongers on the forums had me so paranoid about the increased consumption that I packed 2x 5gal jugs of DEF on a trip across Ontario right after filling up my tank. All I ended up doing was put milage on those jugs because all the precautions were totally unnecessary.

If you're not totally out of touch with your vehicle, you should be able to have a general idea of when to expect running out of DEF.... IMO at least

 

[showdown 42]

Turbo is correct, all that happened was I was inconvenienced while I looked for ad blue on rt 95.What about being 500 miles from home and 1000 miles to go on the trip, someone like you wife ,daughter or son on a Sunday with all the dealers closed.
This is the first time in owning 2 TREGs over 12 years I got a message at 5000 miles from the ad blue fill up that I had 1000 miles to go. In the past I had the ad blue added when I had the oil changed at about 10,000 miles.

 

[TurboABA]

Unless something is wrong with your system, or you've changed your driving pattern\use\style a LOT, you should not run low that fast.
Guys usually run out that soon when towing heavy loads.

They warned you about the increase in DEF use after the fix... but it appears that a lot of owners didn't read the documentation!

Diesel Exhaust Fluid (DEF) consumption - DEF (also known as AdBlue®) consumption for your vehicle may change. Model Year 2015 vehicles may experience an increase of 40% on average, while Model Year 2016 vehicles may on average experience a decrease. The exact amount of the change will vary depending on driving style and other factors. This means some drivers will need to refill the DEF tank more frequently.

 

[TurboABA]

We are the factory that produces Adblue/DEF, if you have bulk demand in this regard, please contact me, you will get a faster and more affordable quotation.

GTFO

 

[Mike in Anchorage]

I don't know why everyone is crying about this so much. If you've owned the fixed vehicle for any amount of time, you should have a decent idea of what your typical usage pattern is like and of what type of DEF consumption rate is to be expected. That alone allows you to "plan" accordingly. If you have a significant tow/trip coming up, top up your tank before you pack. If you're not totally out of touch with your vehicle, you should be able to have a general idea of when to expect running out of DEF.... IMO at least

Depends on the use. Stunning differences of driving at higher altitude, towing at low speed, towing at highway speeds, etc. I've tried keeping a spreadsheet to get an idea in about 15k miles of towing with it. No clear pattern yet, but I've also had some sensor issues that have also affected it dramatically. Also, when the dealer refills it when at the shop, they never can tell you how much they added. Please don't tell my wife how in touch with my vehicle I am. She already wonders why I keep my bike in the tent when I'm cycle touring . . .