Check engine light on, code reads: P203D Reductant Level Sensor Circuit High
Thread Starter
Member
Joined: Oct 2019
Posts: 122
Likes: 24
From: Toronto, ON
ML 350 Bluetec
Check engine light on, code reads: P203D Reductant Level Sensor Circuit High
I am getting this code. I looked up probable causes in general:
Reductant level sensor defective
Wrong fluid in DEF storage tank
Electrical short
I know it is not the wrong fluid, would have shown up before now. Odds on the other two?
Reductant level sensor defective
Wrong fluid in DEF storage tank
Electrical short
I know it is not the wrong fluid, would have shown up before now. Odds on the other two?
Senior Member
Joined: Jul 2017
Posts: 487
Likes: 114
From: DFW, TX
Ml350 bluetec
Likely the DEF sensor/heater unit has become defective. So this will require draining/emptying the tank and then dropping the tank to get at the Heater/Sensor unit. I did this DIY on my 2013 Touareg TDI, hoping that I will never have to do this with my 2014 ML 350 Bluetec. And now it believe this component is being covered by the Lawsuit Warranty, but not sure if Canada is doing the samething.
MBWorld Fanatic!
Joined: Jan 2013
Posts: 3,745
Likes: 811
From: The Great White North
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, Taycan GTS Sport Turismo, C5 Z06 & IS300 race cars
Likely the sensor or the electrical connection (it could be just corrosion). Yes, Canada is going to perform the same recall and repairs on the diesel MLs as the ones in the US, but they haven't yet agreed on the settlement amount hence the delay here. AFAIK the pump / heater assembly in the DEF tank is NOT covered by the recall and warranty (and I think the sensor may be a part of it), but if it is, you'll be able to make a claim for it and get your money back once the settlement is approved.
Junior Member
Joined: Feb 2019
Posts: 35
Likes: 10
From: Canada
ML350 Bluetec 2014
Just wondering, before P203D code, did you just fill up the Adblue fluid?
Thread Starter
Member
Joined: Oct 2019
Posts: 122
Likes: 24
From: Toronto, ON
ML 350 Bluetec
Wish me luck, I am finally taking it in for this today. In the meantime I did have a warning to fill the DEF. I added some and that did go away, so I will find out later today what the issue is. I am in Canada, the US diesel recall/agreement/etc does not apply here. There is a Class Action lawsuit that is not yet resolved.
Trending Topics
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Newbie
Joined: Aug 2021
Posts: 2
Likes: 0
2014 Mercedes Benz ML350 BlueTec
P203D
[QUOTE=Don_CA;8369167]Just a follow up, everything is working great. I did not take it to Mercedes, I took it to a German car mechanic that works on Porsche, BMW, Mercedes and Audi.[/QUO
same issue with my vehicle. 2014 ML350 BlueTec.
Would you mind to share the contact info of the German car mechanic, please?
same issue with my vehicle. 2014 ML350 BlueTec.
Would you mind to share the contact info of the German car mechanic, please?
Newbie
Joined: Aug 2021
Posts: 2
Likes: 0
2014 Mercedes Benz ML350 BlueTec
Would you mind to share the contact info of the German car mechanic, please?
Thread Starter
Member
Joined: Oct 2019
Posts: 122
Likes: 24
From: Toronto, ON
ML 350 Bluetec
Newbie
Joined: Mar 2020
Posts: 3
Likes: 3
From: Oshawa, ONTARIO CANADA
2014 ML350 BLUETEC
Same: 2014 ML350 BLUETEC
Hi folks, same issue , question: last time I filled up the DEF
I used generic fluid. I was told all DEF is the same. Do you think that not using MB ADBLUE is what caused my error code? Vehicle runs fine. Check engine is intermittent. Is there a fix other than replacing the sensor?
I used generic fluid. I was told all DEF is the same. Do you think that not using MB ADBLUE is what caused my error code? Vehicle runs fine. Check engine is intermittent. Is there a fix other than replacing the sensor?
Newbie
Joined: Nov 2017
Posts: 6
Likes: 0
2014 Mercedes ML350 Bluetec
Thinking about ordering the heater online and replacing it.
Did they end up just replacing the entire heater for you? I'm also located in Toronto.
Thread Starter
Member
Joined: Oct 2019
Posts: 122
Likes: 24
From: Toronto, ON
ML 350 Bluetec
They replaced the pump, if the heater is part of that then yes.
MBWorld Fanatic!
Joined: Jan 2013
Posts: 3,745
Likes: 811
From: The Great White North
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, Taycan GTS Sport Turismo, C5 Z06 & IS300 race cars
If you're thinking of doing the work yourself, you can get a Xemodex unit for about half the price. They seem to be at least as good as the MB OEM part. However, you can EASILY bugger other things up in the process (all it takes is for some ammonia crystals to form and you're SOL), so unless you really know what you're doing, you may be better off taking it to Merc.
Senior Member
Joined: Nov 2015
Posts: 272
Likes: 49
From: Ottawa, Ontario
2013 ML350 Bluetec, 1966 Ford Mustang Convertible (sold)
Likely the sensor or the electrical connection (it could be just corrosion). Yes, Canada is going to perform the same recall and repairs on the diesel MLs as the ones in the US, but they haven't yet agreed on the settlement amount hence the delay here. AFAIK the pump / heater assembly in the DEF tank is NOT covered by the recall and warranty (and I think the sensor may be a part of it), but if it is, you'll be able to make a claim for it and get your money back once the settlement is approved.
MBWorld Fanatic!
Joined: Jan 2013
Posts: 3,745
Likes: 811
From: The Great White North
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, Taycan GTS Sport Turismo, C5 Z06 & IS300 race cars
I don't know anything about a potential payout (amount), but the AEM for the W166 is currently being tested on a 2015 ML350. They have to drive it for 15,000km following the AEM installation before the fix is approved, and I don't think it is anywhere near that yet (I was in it a few weeks ago). I suspect it will be early 2022 before we see anything, but the parts are already in various MB storage warehouses.
Junior Member
Joined: Feb 2019
Posts: 35
Likes: 10
From: Canada
ML350 Bluetec 2014
After a cold weather (-30C) long drive, several DEF codes came up, 203D12, P203D, 205D17, P205D, 20E821, P20E8. Seems many related parts inside the DEF tank are not functional now. Just wondering is the DEF pump still working? Seems ML 350 Bluetec cannot handle temperature below ~-30C, happened nearly every winter when temperature drops low.
Newbie
Joined: Sep 2022
Posts: 1
Likes: 0
ML 350
Hi Don. I've just had the same issue occur tonight with my ML 350 bluetec and I was searching the forums to find a solution, when I saw your post. Can you recall what the mechanic did to fix the problem ? (i appreciate that this happened a couple of years ago for you). Cheers, Paul
MBWorld Fanatic!
Joined: Jan 2013
Posts: 3,745
Likes: 811
From: The Great White North
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, Taycan GTS Sport Turismo, C5 Z06 & IS300 race cars
Hi Don. I've just had the same issue occur tonight with my ML 350 bluetec and I was searching the forums to find a solution, when I saw your post. Can you recall what the mechanic did to fix the problem ? (i appreciate that this happened a couple of years ago for you). Cheers, Paul
And, the AdBlue heater / pump / sensor assembly is covered under the AEM (emission modification) warranty, which I am assuming everyone has had performed by now. Just take it to any dealership.
