SEE POST # 527 -DEF head derate emergency/temporary travel procedure

[tom chelbana]

SEE POST # 527. With both Spartan and FL chassis experiencing derating and stop engine problems becoming either a tow or brake down this is what the trucking industry has come with. To assist diesel engine owners with an option when their coach gets a check engine light along with DEF codes there is a option that owners can do to allow them to either to continue driving or avoid a tow. This is option that I know some owners would like to know about and use. This procedure has been posted on irv2 Entegra forum and today I went under our 2018 London Aire on a Spartan K-3 chassis with the Cummins 605 to check the location of the speedometer disconnect, which is on all Cummins engines and shot two photos to show where this connection is located. It is located on the transmission on the DS (right) side. By disconnecting this speedometer sensor this will allow you to operate your coach to drive to location to repair DEF head or until the time the DEF heads are available with out being derated or shut down. With the speedometer sensor disconnected your coach will not have a speedometer. Some owners will not be interested in this emergency/temporary procedure, but I would, if the DEF head problem caused me to be broken down along the highway.
Newmar Man

[Dutchstar411]

Originally Posted by tom chelbana

With both Spartan and FL chassis experiencing derating and stop engine problems becoming either a tow or brake down this is what the trucking industry has come with. To assist diesel engine owners with an option when their coach gets a check engine light along with DEF codes there is a option that owners can do to allow them to either to continue driving or avoid a tow. This is option that I know some owners would like to know about and use. This procedure has been posted on irv2 Entegra forum and today I went under our 2018 London Aire on a Spartan K-3 chassis with the Cummins 605 to check the location of the speedometer disconnect, which is on all Cummins engines and shot two photos to show where this connection is located. It is located on the transmission on the DS (right) side. By disconnecting this speedometer sensor this will allow you to operate your coach to drive to location to repair DEF head or until the time the DEF heads are available with out being derated or shut down. With the speedometer sensor disconnected your coach will not have a speedometer. Some owners will not be interested in this emergency/temporary procedure, but I would, if the DEF head problem caused me to be broken down along the highway.
Newmar Man

Thanks Tom, that's good to know for sure

DS drivers side should be the left side, passenger would be right side. So the DS is the drivers side correct?

[R.Wold]

I’ve read about this elsewhere, and apparently it’s common knowledge among truckers. I Definitely would try this over experiencing another derate. I can live without a speedometer anyway, but anyone with a GPS that displays their road speed can use that instead. Mine does so having the in dash speedo off would be a non-issue to me.

[mbrooking]

Awesome information for sure! Thanks
(Oh, and I'm betting Tom is using Newmar terminology... DS is for Door Side.)

[Ljwt330]

Question.

Will this disconnecting of the sensor work only before a derate happens, or will it “cure” a derated situation? I suspect it must be done as soon as a code is registered.

[R.Wold]

Originally Posted by Ljwt330

Question.

Will this disconnecting of the sensor work only before a derate happens, or will it “cure” a derated situation? I suspect it must be done as soon as a code is registered.

I think you’re right. So if you’re already at 25% derate, it wouldn’t reverse that, but would keep it from derating further.

[Dutch Star Don]

Here is a file I posted before with derate info....

Cummins DEF-Related Warnings.pdf

[tom chelbana]

As this information gets out we should start hearing about questions like if the engine has already starting derating, if full performance will return. For us, we would pull the plug on the speedometer as soon as it was indicating the DEF codes and the check engine light is on. Won't wait to be at the point were derating and stop engine are already on. Would request if anyone using this speedometer disconnect to operate their coach because of DEF/check engine to share with the Newmar irv2 owners.
Newmar Man

[tom chelbana]

Sorry for using DS which I used for Driver Side our left side.
Newmar Man

[Dieselgem]

When I posted this in the Entegra forum, I had found it searching for a way to continue if the know codes were thrown. It seemed like it could be worth a try for those of you with newer vehicles who are having def head issues. Evidently it is something some of the truckers with Cummins engines are trying. I hope it works.

[greeneville1]

This option provides a possible way to proceed on your travel to a repair shop (Cummins Shop or other) without the nagging fear that your coach will suddenly derate or stop on a busy interstate highway. We suffered the dreaded DEF fault codes in our 2018 Allegro Bus 40AP. Tiffin overnighted us the replacement unit and I was able to change it myself. Even though we now have a 2021 45`OPP, I still scan for fault codes constantly. Thoughts of being stuck on a interstate narrow shoulder with 85 mph traffic is worrisome. Thanks very much for sharing this info. This may be the best information post that we have ever received from IRV2. Stay Safe.

[sramer]

That's great information Tom, thanks for sharing.

[zman62]

Has anyone actually driven with the speed sensor disconnected? Usually the speed sensor feeds info to many things other than the speedometer. This is how the transmission knows when to shift among many other things going on. Maybe they are using more than one speed sensor?

[Rev. Roy]

Thanks Tom! Someone raised the concern of the transmission being controlled by the speed sensor. Am I wrong in my thinking that the transmission shift-point is controlled by the RPMs not the speed? It's been too many years since I did engine/transmission work.