Fault Codes

Trailer Marker Lights Not Working — Where to Check First You walk around the trailer doing a pre-trip check and […]

Trailer Clearance Lights Not Working — What to Check on the Tractor The clearance lights — the lights along the

Trailer Turn Signal Lights Not Working — Diagnosis Starting Point You signal a turn, and the trailer’s signal lights don’t

AC Throwing Hot Air? The 3 Most Likely Causes in Order The AC is on, the fan is blowing, but

Volvo D13 Headlights Not Working — Why a Fuse Won’t Fix It Headlights go out on a Volvo VNL with

Trailer Stop Lamps Not Working — Fuse, Relay, or Wiring? You hit the brakes and the trailer’s stop lamps don’t

Truck Won’t Go Into Gear After a Cold Start — What’s Happening You start the truck on a cold morning,

Fan Clutch Stuck On — Loud Fan Noise and Engine Running Cool You notice the engine fan is roaring constantly

Truck AC Not Blowing Cold? Common Causes and Fixes The fan is running, air is coming out of the vents,

Blower Fan Not Working in Your Truck? Here’s What to Check You hop in, hit the fan switch, and nothing