CM870 Turbo Underspeed and Overspeed

[pwhittle]

Hello,

My CM870 (factory stock) ISX15 525hp has been derating with Turbo Overspeed (max 32 psi boost) for a while, and has just started throwing Turbo Underspeed codes at low speeds. I first noticed it in some stop and go traffic on the last trip.

I have Insite and some logs of the Overspeed, but have not logged the Underspeed code occurring yet.

What should I be looking at?

Thanks

Paul