Emergency DEF bypass

[WinePress]

I saw a post, can’t find it now, that linked to a website that laid out a kit to build that would bypass the sensor issues. Can someone direct me to this? I’d like to have one in case I get stranded on my journey to Hawaii.
Thanks in advance……

 

[CaptainGizmo]

To do this right, it’s not cheap. Additionally, the components can be hard to obtain currently.

Depending on your DEF system, I may be able to you a DEF Head Emulator from Custom Coach Products.

Feel free to drop me a DM and I’ll get info from you.

 

[redbaron]

defsim.myervin.com

 

[Rich W.]

RB’s link is correct ( DEF Sensor Simulator ), its about $150 to build, but it will only work on 2016 and later chassis (my 2016 coach is on a 2015 chassis so not compatible) and as designed, it is only compatible with Spartan chassis coaches and some Tiffin (Powerglide chassis?) models with solid-state DEF level, temp, and quality sensors.

To make it work with 2016 and later Freightliner coaches you have to acquire the correct 4-pin (CAN-bus) connector (now also detailed on the website).

Pre-2016 Freightliner coaches have a float for sensing DEF level and the signal can be emulated with the correct resistor, but I don’t have that information readily available. Easy to figure out though (see TSB below).

So while an excellent adjunct for compatible units, its pretty limited. It also only overrides the sensors in the tank, so you still have to run DEF or you will get SPN codes from your SCR telling you your NOX levels are too high, and still be derated.

Also it appears that as of around late 2020 Freightliner DEF headers (TE connectivity) nearly eliminated the false low DEF failures. DEF heads from Shaw Development used in Spartan and Powerglide chassis are said to be more reliable as of Gen 7 but that remains to be seen.

So to get a more specific answer on what you can do both as preventative measures, and for contingencies, list your coach chassis year, make, and model. But don’t just buy the parts and build the DSS without confirming that it will work for you.

There’s a lot you can do on your own to increase the reliability of your coach and your confidence in your emissions system. I’ve had three parts failures resulting in derates, but my last trip (7700 miles) was completely emissions-trouble free. Had my share of other issues, but not a peep from the emissions side.

This TSB: https://static.nhtsa.gov/odi/tsbs/2013/SB-10054667-8295.pdf has a lot of useful information on keeping your system working and correcting problems, and includes the correct resistance reading for pre-2016 DEF level sensors if you want to go that route.

 

[WinePress]

Thanks for everyone’s input. I’m on a FL chassis so I will do more research on the adaptability from the Spartan connector to the FL. I did disconnect, clean and reconnect all the connections, including the PCM. Problem cleared, but I would like to be proactive with a solution to solve a potential non drive issue.

 

[laurens]

To do this right, it’s not cheap. Additionally, the components can be hard to obtain currently.

Depending on your DEF system, I may be able to you a DEF Head Emulator from Custom Coach Products.

Feel free to drop me a DM and I’ll get info from you.

I do not want to delete the def But.
I do want to Find an emergency Is temporary bypass That will allow me to get home To my mechanic. I use my van for work and often many states away From the house and don't want to get stranded on the road

 

[Jim]

I do not want to delete the def But.
I do want to Find an emergency Is temporary bypass That will allow me to get home To my mechanic. I use my van for work and often many states away From the house and don't want to get stranded on the road

Broken DEF Header and possible workaround

There has been a lot of notice given to the DEF header recently, mostly because so many of us are experiencing DEF Header failures and having to replace them. I’m in that group, and during the days that it took me to sort through the workings of this beast, I’ve learned some things that could...

rvforums.com

 

[Roadglide117]

Since you didn't mention what yr your coach is, you may not need one. The problems are with the coaches that have digital systems, not with the analog systems.

 

[Jim]

I do not want to delete the def But.
I do want to Find an emergency Is temporary bypass That will allow me to get home To my mechanic. I use my van for work and often many states away From the house and don't want to get stranded on the road

If it's the temp switch, (probably not the correct name for this part) and it generally seem to be, you can put a clamp on the intake/return hoses to stop the flow of hot fluid from entering the def header. Once everything cools down and the error clear, you should be OK to proceed.

 

[Rich W.]

Since you didn't mention what yr your coach is, you may not need one. The problems are with the coaches that have digital systems, not with the analog systems.

This is the most common problem with pre-2016 emissions: https://static.nhtsa.gov/odi/tsbs/2013/MC-10142383-9999.pdf.
Anything with DEF can leave you stranded if you don’t understand the system and/or are not prepared to correct problems as they occur.

That said the DSS will not work on pre-2016 emissions for the reasons Roadglide stated.