Semi-Truck Dashboard Warning Lights


Understanding what each semi-truck dashboard light means can help you identify potential problems in your vehicle, allowing you to keep your rig in the best condition possible. These lights can also assist you in keeping up with maintenance and promote a longer life span for your semi-truck. The location and symbols of these warnings will vary based on the truck's age and model, and newer models may have additional lights as technology advances.

However, all semi-trucks have some common warning lights to help you identify potential problems with your vehicle, such as the check engine, coolant and oil lights. Learn more about semi-truck dashboard lights' meanings and what you should do if you encounter one of these indicators while driving.

Most Common Semi-Truck Warning Lights

Semi-trucks are equipped with warning lights to let drivers know if there's a potential problem with the engine or the electrical system. These lights are critical for keeping truck drivers and other motorists safe. When these lights appear, it can indicate problems ranging from minor to severe. 

In most cases, these warning lights are an early alert to give you time to visit a professional, so you generally don't need to panic when you first see one. However, there are some instances where a warning light can indicate a serious problem that needs to be checked or repaired immediately. Below, you'll learn more about the different semi-truck warning lights, what they mean and what actions you should take to address them.

Check Engine Light

The check engine light on semi-trucks is one of the most common warning lights on the dashboard. Appearing in the shape of an engine, check engine lights are usually yellow, orange or amber and will either blink or remain continuously illuminated. This light is a quick and easy way for drivers to identify something wrong under the hood. Check engine lights can mean anything from a loose gas cap to a problematic catalytic converter.

You don't need to be alarmed if the check engine light comes on while driving. A semi-truck check engine light is generally an initial warning that something is wrong and often indicates a minor issue. However, you should see a mechanic as soon as possible so they can perform diagnostics to determine what's causing the light to turn on. A mechanic can help you determine whether the issue is minor or if you need to repair your truck before continuing your journey. 

Oil Light


If the oil light comes on in a semi-truck, it usually indicates one of two problems — engine oil pressure or engine oil level. The indicator often looks like an oil can, though some models may use a light that says "OIL" in big letters. In most cases, the oil light indicates that the oil in your engine is too low and needs to be topped off.

If the light turns on while driving, find a safe spot to pull over and try to determine why the light is visible. While insufficient oil is the most common culprit behind an illuminated oil light, it can also indicate that you need an oil change, the oil has become too viscous, or you have a leak. If you've topped up your oil, but the light remains visible, you should take your semi-truck to a professional to check it for other potential problems. 

Coolant Level Light

The coolant level light usually resembles a thermometer or box and uses wavy lines to indicate liquid. Usually, this light turns on to indicate that your engine coolant level is low, so you'll need to have your semi-truck looked at as soon as possible. If you cannot stop soon, you should monitor your semi's temperature gauge to ensure your engine isn't getting too hot. If your engine overheats, it can cause permanent damage and require costly repairs. 

A professional can also help you determine if your coolant levels have dropped naturally over time or if you have a leak. A leak must be repaired promptly to prevent the loss of coolant while you're on the road, especially for long journeys where you may not be able to stop often. 

ABS Light

Anti-lock braking systems (ABS) are sophisticated systems that allow heavy semis to significantly reduce the distance required to brake. These systems are essential in preventing accidents between semi-trucks and other motorists. If a semi-trailer ABS light flashes on your dashboard, it may be due to the following:

  • Broken sensors
  • Low battery voltage
  • Poor wheel bearings
  • Bad modules

If your ABS light is blinking or turned on, you'll want to prioritize having it checked by a professional. A malfunctioning ABS on a semi-truck can put you and others at risk on the road. 

If you're wrapping up a short trip, you could probably have your semi-truck checked at the end of your drive, but you should keep a careful eye out and use caution when driving, even if it's just a few miles. However, if you've only just started a long trip or have many miles left to go, you may want to stop to have your ABS inspected before continuing so you can keep yourself and others safe. 

Tire Pressure Light

Many newer semi-trucks use a system to monitor tire pressure to let drivers know when a tire needs more air. Low tire pressure can increase the risk of blown tires, creating a hazardous situation on the road. Low tire pressure can also increase fuel usage and result in higher operating costs. Tire pressure lights often turn on before a blowout when tire pressure drops below recommended levels. This light doesn't indicate an emergency, but you should stop at the next available place to top off your tires. 

Many truck stops will have areas for you to check and adjust your tire pressure. If you refill your tires and reset the light only to see it reappear a short time later, you may have a slow leak that needs to be patched. If this is the case, take your truck to a shop so the leak doesn't remain an ongoing problem.

Contact Thompson Truck Source for Immediate Field Service

The health of your semi-truck is essential to your ability to haul important cargo from one location to the next. If your semi-truck suddenly breaks down or a warning light comes on during your drive, it can slow you down and cause unnecessary stress. Fortunately, if you're located in Alabama or northwest Florida, Thompson Truck Source is here to help with our 24/7 field service.

We can repair unexpected mechanical problems at any time of the day to reduce your downtime and keep you on schedule. We also offer other services to help you keep your semi-truck in good condition on and off the road, such as preventative maintenance, fluid sampling, engine overhauls and more. Contact us today for immediate field service or to learn more about our offerings.