My RV (which is on a Sprinter chassis) had been sitting for a month on an incline, and when I came back the check engine light was on. It threw the codes:

> P2506 (ECM/PCM Power input signal Range)
> P040D (EGR Temperature Sensor "A" Circuit high)
> P0544 (Exhaust Gas Temperature sensor Circuit [Bank 1 sensor 1])

Still in the process of finding anything relevant on YouTube. Any insights into this?