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Dashboard warning lights are more than just symbols; they are your truck’s early warning system for everything from minor maintenance needs to major mechanical issues. Knowing what each light means and responding appropriately can save you time, money, and prevent roadside emergencies. In this edition of the Maintenance Monthly, we are going to breakdown some of the most important semi-truck dashboard warning lights and how to handle each one safely and effectively.
Color: Amber | Audible Warning: Yes
This light indicates a potential issue with the engine or emissions system. It could stem from something as minor as a loose gas cap or as serious as a cylinder misfire. If ignored, it may lead to reduced performance or long-term engine damage. The onboard diagnostics system can be scanned for error codes to pinpoint the problem.
What to do: Schedule a diagnostic test and service the issue promptly to avoid escalation.
Color: Amber | Audible Warning: No
The MIL light, while similar to the check engine light, can also cover a wider range of powertrain and emissions issues. It’s often triggered by a failing sensor, fuel mixture problems, or emissions control faults. Though not always urgent, continuously driving with this light on can lead to decreased fuel economy or emissions compliance violations.
What to do: Note any performance changes and have your truck checked at your earliest convenience to prevent potential breakdowns.
Color: Amber | Audible Warning: Yes
This light alerts you to elevated exhaust system temperatures, usually during DPF regeneration. These high temperatures are normal but can become dangerous near flammable materials or when idling in enclosed spaces. Ignoring this warning could result in fire hazards or exhaust component damage.
What to do: Allow the regeneration process to finish, avoid parking near combustible surfaces, and don’t shut the truck down prematurely.
Color: Amber | Audible Warning: No
This system helps maintain control during skids or emergency maneuvers by adjusting braking and power. If the light flashes, the system is actively working. If it stays on, it indicates a malfunction in the sensors or control system.
What to do: If the light remains on after starting the truck or during normal driving, have the system inspected. Driving without a working ESC system may increase risk during adverse weather or road conditions.
Color: Red | Audible Warning: Yes
This is one of the most critical alerts on your dashboard. It typically signals serious engine issues like extremely low oil pressure, overheating, or coolant loss. Continuing to drive can result in catastrophic engine failure.
What to do: Safely pull over, shut off the engine immediately, and contact a mobile service technician or a towing service to transport your truck to the nearest repair facility. Do not restart the engine until the root issue has been diagnosed and addressed.
Color: Amber | Audible Warning: Yes
This warning light indicates that the ABS system on the trailer is not functioning properly. Without ABS, the trailer is more likely to skid or jackknife during hard braking.
What to do: Check trailer connectors and wiring for faults. Schedule a service appointment for the trailer brake system before continuing on longer routes or steep grades.
Color: Amber | Audible Warning: Yes
This light comes on when the truck’s ABS detects a fault in the system. While basic braking remains functional, the safety net ABS provides, such as preventing wheel lock during emergency stops, is compromised. In slippery or wet conditions, this can significantly increase stopping distance.
What to do: Drive with caution and arrange for a technician to inspect the ABS system and repair it before driving in high-risk areas.
Color: Amber | Audible Warning: No
This light informs the driver to wait while the glow plugs preheat the engine cylinders. Starting before the indicator turns off can lead to poor starts, excess smoke, or engine knocking in cold conditions.
What to do: Always wait for the light to go out before turning the ignition. If the light does not appear at all, have the glow plug system checked.
Color: Amber | Audible Warning: Yes
This alert indicates a fault in the transmission system, such as overheating, slipping gears, or fluid pressure loss. Ignoring it may lead to transmission failure or vehicle shutdown.
What to do: Stop and check transmission fluid levels if possible. If the issue persists, reduce load and speed, then head to the nearest truck repair shop immediately.
Color: Amber | Audible Warning: Yes
This light shows how full the diesel particulate filter is. As the soot builds up, the system will require regeneration to prevent clogging. If ignored, performance will drop and severe engine and/or DPF damage may occur.
What to do: Follow the prompts for passive or active regen. If manual regeneration fails, seek immediate service to avoid engine shutdown.
Understanding and responding appropriately to your truck’s dashboard lights is one of the simplest ways to ensure safety, maintain uptime, and reduce repair costs. These indicators provide insight into critical systems and ignoring them could mean serious safety and financial consequences. Always refer to your truck owner’s manual for exact symbol definitions and consult a certified technician when unsure. Need to schedule a service to get your truck diagnosed or repaired? Schedule a service with a certified technician at any of our nine full-service Kenworth of Pennsylvania locations today.
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