"DEF Contaminated" alert

[NCRog]

Here we go again, maybe!

The other day, after about 3 hours driving in N Florida, I got an amber "DEF Contaminated" alert. No other lights, no apparent change in engine response, just the light. I last filled up with DEF about 3 weeks ago, no issues up to this point. However, out of an abundance of caution, I pumped out the 6 gallons of DEF in the tank and replaced with fresh. Both the old and new tested at 32.5% urea, on spec, and the old had no signs of cloudiness.

A week later, we made our next leg, no lights initially ... although I did briefly have an "Emissions" amber light at engine start, which disappeared after a few seconds. Then, about 2 hours later, the "DEF Contaminated" light flashed on and off. It reappeared and the frequency increased until it became solid again. By the time we reached our overnight stop the warning was accompanied by a "DEF Sensor Failure" alert. The next morning all was well again, except for the momentary emissions light the alerts had cleared, until 2 hours into the trip, when the contaminated alert started again.

Have any others experienced these symptoms? I went through the DEF head failure on our '17 Essex, but there you knew something bad was going on. In this case it's almost as if the system is OK and overheats or something ... oh, and the DEF gauge doesn't appear to move. In this case the OBD screen shows a number of entries, all an FMI=5 with SPN codes of 523XXX and 524XXX, but they're gone when I restart the engine.

My current challenge is to try and get a diagnosis and resolution here in SWFL, easier said than done. If you didn't purchase from the local guy it's a 2 month wait for an appointment!

[Ron L55]

First day-DEF contamination, drove for 250 more miles no problem
Second day-NOTHING, drove fine
Third day-DEF head frailer... Drove 100 mile to LIMP. Installed Simulator and drove for three more days.
Had Head replaced under Warranty.
2022 DS 4081 15252 miles.
Question: These Law Makers & Manufactures must not own a DEF vehicle. Because if they did and went into LIMP mode, they would get these HEADS figured out.

[Archer2]

Check to make sure that your DEF tank heater solenoid has not failed open and is letting hot coolant circulate thru your DEF fluid.
Compare the temperature of the heater hose on the DEF header inlet With the engine cool and compare to the temp with the engine at operating temp. The inlet hose should not be hot to the touch. If it is it indicates the solenoid valve has failed.
Because if the way the sensor calculates the fluid density to extrapolate the fluid “quality”, if the temp is too hot it causes a false “bad quality” fault.
You can just permanently pinch off the inlet hose where it goes into the sensor with vice grips or a hose pinch off tool. As long as you never operate when the ambient temps are close to 11°F there is no need for the heater solenoid to be open.

[NCRog]

Appreciate the feedback ... Archer2 thanks for the insight and items to check. That makes sense. After the 2021'ish round of sensor head failures I was paranoid about actual DEF inlet temperature. On my 2017 Essex I was able to display DEF temp on the driver's Silverleaf display. Several times I would see numbers of 120+ deg F. The DEF tank sits in an area where it gets a lot of radiant heat from the turbo crossover pipe, so I added an additional heat blanket to the pipe ... seemed to prevent such high DEF temps after driving for several hours. The 2023 Essex switched to a Valid dash display, so that large data pool is not readily accessible. Anyway, I will check the hose temps with the engine running. It would also explain why it takes a couple of hours before I get an alert. I'm assuming the heater solenoid is part of the DEF head assembly?

After striking out with yet another couple of sources to help me get back on the road safely I've broken down and ordered a DEF simulator. Should be here early next week and I will then have peace of mind about not getting stuck in limp mode, or totally stranded at the side of the road. Although, if it is a failed heater solenoid, clamping off the hose might also be beneficial.

This solution has also lowered my blood pressure. I can understand that the service industry needs to differentiate between the service they provide to their coach customers and/or fleet operators, but to essentially ignore (or push out by 2+ months) service requests when someone has been referred by the chassis OEM for roadside assistance is not what I expected. I now have the ability to head home, if necessary, to get it replaced by my local dealer.

[Archer2]

Actually the coolant valve and solenoid (all one assembly) is normally located external to the DEF sensor. You can find it easily by following the sensor coolant heater hose back upstream.
You will soon find the valve, it should be the first thing you come to but frankly, unless you plan to operate in temps below around 20°F or colder, there is zero reason for the existence of the entire coolant loop and solenoid valve.
I installed a manual ball valve in the sensor inlet coolant loop and turned it off, probably for good. It’s been off for more than 5000 miles now with zero issues.

[NCRog]

The idea sounded great, but after running at high idle for about 45 minutes, with all the engine bay coolant lines feeling really hot, the coolant lines at the DEF head remained cool. So, I guess it must be somewhere in the DEF head, glad I have a simulator en-route!

[NCRog]

Here's the final update ... and hopefully closure.

I waited the 2 months (thank goodness we'd planned to spend a few months in SWFL), then took it into the local Newmar dealer. They managed to pull a couple of failure codes from the system and declared I needed a new DEF head. More waiting, but after another 2+ weeks I finally had a new unit installed.

The DEF quantity indication is a little sketchy, no other emissions related dash warnings, I did use a dipstick to double check the DEF tank, so the indication might be right. When I had the DEF head replaced on our '17 Essex the quantity indication took a refill before it read correctly ... maybe this new one has the same issue. One possible conclusion based on the current quantity reading, validated by the dipstick, is that the system wasn't using any DEF for the 400 miles I was receiving the contamination warnings? Anyway, I'll see how it goes ... I now have a simulator if it ever happens again.