The is a manufacturer-specific extension (used by JLR - Jaguar Land Rover). In Land Rover’s proprietary diagnostic language, "-31" typically translates to: "Signal is missing / No signal / General signal failure."
Never throw a new RCM at the problem without proper diagnosis—you could spend $1,000+ and still have the same code. Invest in a quality JLR-capable scanner or pay a specialist for one hour of diagnostic time. That hour could save you thousands. land rover u0151-31