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Dashboard warning lights are more than just illuminated icons on your semi-truck’s dash, they are critical signals that keep you informed about the health and safety of your vehicle. In a previous edition of our maintenance monthly, we covered some of the most common alerts. However, there are still several other important indicators every truck driver should recognize. In part two of our dashboard warning light series, we will take a closer look at some additional alerts, what they mean, and the steps you should take if they appear.
Color: Red | Audible Warning: Yes
This warning suggests the battery is not charging, likely due to a faulty alternator, broken belt, or corroded connection. Without charging, the truck may eventually lose power, affecting lights, HVAC, and engine controls.
What to do: Turn off non-essential electrical systems and have the charging system checked right away.
Color: Red | Audible Warning: No
This simple indicator lets you know that the parking brake is engaged. It prevents the truck from moving while parked and should not be on while driving. Moving the truck with the brake applied can cause brake/tire wear or drivetrain damage.
What to do: Make sure to fully release the parking brake before moving the truck. If the light stays on after release, check for a stuck brake valve or sensor issue.
Color: Amber | Audible Warning: No
This light flashes when the traction control system is active, limiting wheel spin to maintain grip. If it stays on, there may be a fault with the system or related sensors. Driving without traction control can lead to slipping or fishtailing on slick roads.
What to do: If traction control appears disabled, drive cautiously in wet or icy conditions and schedule a service appointment as soon as possible.
Color: Red | Audible Warning: Yes
This critical light signals that the truck’s air brake system has lost pressure or is failing. Without functioning air brakes, the truck may not stop safely, creating immediate danger.
What to do: Pull over as quickly and safely as possible and call for roadside assistance. Do not continue driving until the issue has been repaired.
Color: Amber | Audible Warning: Yes
This light indicates an issue with the hill start assist system, which helps prevent the truck from rolling backward when starting on an incline. A fault in this system may mean it won’t engage when you need it most, increasing the risk of rollback accidents. The problem could stem from faulty sensors, low brake pressure, or a system calibration error.
What to do: Use extra caution when starting on hills if this light is on. Have the system inspected and repaired promptly to restore safe and reliable operation.
Color: Amber | Audible Warning: Yes
This system shuts down certain electrical loads when battery voltage drops too low to preserve enough power for essential functions. If the light comes on, it is a warning that the truck’s electrical supply is under strain.
What to do: Limit use of non-essential electronics and check battery condition, alternator function, and wiring for problems.
Color: Amber | Audible Warning: No
This light means the truck’s automatic engine start system has engaged, usually to maintain battery charge or cab climate while parked. It’s not typically a cause for concern.
What to do: Monitor that the system operates normally. If the light stays on when the system should be inactive, schedule a diagnostic appointment.
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: Red | Audible Warning: Yes
This light comes on when the engine is operating above its safe RPM range. Running an engine beyond redline can cause severe damage to pistons, valves, and other internal components.
What to do: Reduce engine speed and shift to an appropriate gear. If the light comes on frequently, have the engine and transmission checked to prevent long-term damage.
Color: Red | Audible Warning: Yes
This critical warning indicates a severe issue with the truck’s transmission, such as overheating, slipping gears, or low fluid pressure. Continuing to drive could cause complete transmission failure.
What to do: Pull over safely and call for service. Continuing to drive risks costly repairs or permanent transmission damage.
Commercial truck dashboard lights are designed to keep you informed and your truck operating safely. Taking them seriously not only helps prevent costly breakdowns but also ensures you are protecting yourself and others out on the road. When a light comes on, do not ignore it. Understanding what it means and acting quickly can make all the difference. Always refer to your truck’s manual for exact details, and if you are unsure, trust a certified technician to get to the root of the problem.
Need expert diagnostics or repairs? Our service team is here to help keep your truck and your business moving. Schedule a service with a certified technician at any of our nine full-service Kenworth of Pennsylvania locations today!
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