Limp mode explanation / questions & answers

[2022 Tradesman]

I've heard that if certain maintenance isn't achieved or neglected in some cases regarding diesel engines, that it can cause the vehicle to go into limp mode.
My dashboard prompts a message when I'm low on DEF fluid and it states that if I don't get the fluid in the truck soon my truck will go into limp mode, stating I'm not to exceed 5 miles an hour. Okay simple enough I suppose, but since I've never encountered my truck going into limp mode, I'm curious if the message is recommending me not to drive over 5 mph, or does the truck actually govern the engine restricting it's speed to 5 mph?? Just curious... I've heard people talk about limp mode and ask the veterans for their advice on resolving the matter, but what really happens when your truck goes into limp mode?! Thanks in advance!

 

[mtnrider]

Yes, your truck will be limited to 5mph. "Limp" mode is usually associated with a problem/issue with the truck, not so much a lack of maintenance but I've never run the DEF that low to see that message. You run out of DEF though and it will limit the truck. I would never let it get that low myself, just like my fuel.

Be very careful about what you read on the "internet", specifically social media. LOTS of paranoia and false information about diesels out there.

Fill up the fluids when needed, follow your manual for maintenance and enjoy the truck, it's really that simple.

 

[Fake-Account27]

2nd @mtnrider

There is a lot of misinformation out there. I had a check engine light due to what I suspect was an improper regen cycle, which solved itself after about 50 miles of driving. Never went into limp mode. I ended up going to a diesel shop to run a manual regen just to be safe. The first thing the mechanic checked was the DEF level, because it seems the most common issue is not adding DEF.