Transmission not shifting. Is this limp mode?

In the past 3 days, my 2006 has occasionally been stuck in what I think is 2nd gear. It has happened once a day, and seems to "reset" the next time I drive it.
The check engine light is on, but has been for a bad glow plug, so I'm not sure yet if there is a new code.
Everything else seems fine, engine & turbo are purring nicely and no clunks coming from tranny.

I'm just wondering if this is "limp mode" or any other ideas before I take it in…

Thanks!

Sure sounds like limp mode. Could be any number of things causing it. Be careful who you take it to. A Dealership isn't always knowledgeable.

When I lost a speed sensor in my NAG1, I could only get to second gear sometimes; lost reverse during this time as well. Shutdown/restart was a temporary fix.

-Jon

That happened to me once. Pulled over and called a more experienced Sprinter friend. He told me to shut off the motor, wait 5 mins and restart. Worked fine. I was worried but it hasn't happened again. I credit this to having serviced the trans and replaced the sensor plug. Also reduced RSN from minor and frequent to minor and less frequent.