RPO

K34 is factory electronic cruise control. The code matters because it tells you the module, clockspring and brake switch are there — not just the buttons on the wheel.

UK3 is steering wheel mounted controls. If you are changing the radio, this is the code that decides whether you need a steering wheel control interface.

NP5 is the leather-wrapped steering wheel, the alternative to NK5. What it does and does not tell you, and the honest options for a worn rim.

NK5 is the standard urethane steering wheel. It matters in one situation: ordering a wheel, clockspring or airbag and needing to know which part the truck takes.

JL1 is the factory integrated trailer brake controller. GM’s own 2022 documentation says it requires Z82. How it differs from an aftermarket controller, and what to do on older trucks.

FE9 is not an option, it is a federal emissions certification. What it means for catalytic converters, EVAP parts and registering the truck outside California.

K05 is the engine block heater. The element and the cord are separate parts, which is why so many K05 trucks appear to have no heater at all.

KNP is the auxiliary external transmission oil cooler. Transmission heat is what kills a towing drivetrain, and this is the code that says you got the cooler from the factory.

KC4 is an engine oil cooler — not the transmission cooler, which is KNP. How to find it on the truck, and why the two codes get confused constantly.

NZZ is GM’s off-road skid plate package. Usually bundled with Z71 — GM says so for 2016 — but it is its own code, and it is the one that proves the plates were fitted.