What to Do If Your Semi-Truck’s Check Engine Light Comes On

At least 6% of crashes in trucks are due to mechanical failures. Other researchers estimate this to be higher, at around 9% to 18% of all truck-related crashes.

Either way, there’s no doubt that vehicle defects are a crucial player in big rig collisions.

It’s crucial to pay attention to your semi-truck engine light. Note, though, that a lit engine light doesn’t automatically mean you have a busted engine. However, it’s a sign or a warning that not everything under the hood is doing great.

So, what exactly does it mean when your engine light comes on? Is there anything you can do on your own to address the issue?

This post will show you the basics of solving engine light-related issues, so be sure to read on.

What Is the Check Engine Light Anyway?

In some vehicles, the “Check Engine” light can take the form of a “Service Engine Soon” light. It can also be an image of an engine or just the word “Check” that lights up in yellow, orange, or red. 

They exist for the same purpose, to tell you that something isn’t right under the hood.

Dashboard indicator lights have been around since the 1980s. They’re a part of an on-board diagnostic (OBD) system, a built-in computer that monitors and regulates engine performance.

Note that commercial vehicle drivers, including truckers, have federal OBD requirements to meet. Many of these have to do with the use of emission-related electronic sensors. Others are to ensure the overall safety and function of semi-trucks.

With that said, one of the key roles of your truck’s OBD system is to regulate engine speed. It also facilitates fuel mixture, ignition timing, and even automatic transmission shifts.

If the OBD system detects a problem in the electronic control system, it will try to correct it. If it’s unable to, then the computer will notify the driver.

This warning takes the form of either a lit “Check Engine,” “Service Engine Soon” light, or will light up that engine diagram.

Should You Stop Driving If Your Semi-Truck Engine Light Comes On?

When your engine light comes on, it doesn’t necessarily mean your engine is about to sputter and die. If the light is yellow or orange, you don’t necessarily need to pull over, but you should bring your truck in for service as soon as possible. 

If the light blinks non-stop or glows red (either solid or flashing), you’ve got a more severe problem. A glowing red engine light means you should pull over once it’s safe to do so and call roadside assistance – your engine is in imminent danger of a breakdown. 

What Does a Red or Blinking Engine Light Mean?

An indicator that lights up in red or blinks non-stop is a sign of an emergency. A red or a blinking check engine light on a semi-truck often means a severely misfiring engine.

This can happen if loads of unburned fuel gets into the exhaust system. It’s an emergency as it can result in massive damages to a truck’s catalytic converter.

A severe engine misfire can also lead to your truck’s cabin filling up with the smell of gas. Moreover, it can cause your vehicle to release excessive exhaust fumes.

If these other signs occur with a red or blinking semi-truck check engine light, cut down on power right away, and get to Kelly’s ASAP. 

Otherwise, you risk further significant damage to your engine or catalytic converter. If this happens, you can expect a much more expensive repair bill.

What About a Steady Check Engine Light?

A yellow or orange engine light that comes on and remains steadily lit isn’t an emergency- yet. You might still have to schedule it for inspection and possible repairs, though. However, there are some things that you can do on your own that may get that light to turn off.

Top Your Fluids Up

Exhaust gases from vehicles account for up to 40% of man-made nitrogen oxide emissions. NOx emissions are harmful to humans, animals, and the environment. Of the most dangerous NOx gases, however, nitrogen dioxide (NO2) takes the lead.

It’s because of this that regulations on vehicle emissions have become more stringent. This is especially true on big semi-trucks, which have the highest emissions of all motor vehicles.

With that said, commercial diesel trucks now have to use nitrogen oxide (NOx) sensors. In addition, truck engines now come with particulate filters (DPFs). They make up part of the modern truck’s after-treatment systems.

The goal of after-treatment systems is to help reduce the emissions of trucks. However, since they are more innovative, they are much more sensitive.

Something as simple as low exhaust fluids can trigger them. If this happens, they’ll cause your semi-truck check engine light to come on. You may only have to top up on the fluids that you’re running low on in this case.

Tighten Your Gas Cap

Tightening your gas cap only applies to trucks that don’t have a separate indicator for this. If your rig doesn’t have a separate loose gas cap indicator, try tightening the gas cap, as the loose cap may trigger your OBD system.

If the light doesn’t go off, and you’ve noticed fluids dripping under the hood, you may have a fluid leak. In this case, it’s best to have your truck inspected by a Kelly’s technician.

Never Ignore a Lit-Up Semi-Truck Engine Light

A semi-truck engine light that comes on shouldn’t make you panic, but you should be a bit concerned. Whether it lights up in red, orange, or yellow, it’s something you should pay attention to. After all, it is a warning that can help you prevent your truck from stalling and dying.

Most importantly, a fully functioning engine helps reduce your risks of getting into accidents.

Have you tried the DIY fixes we mentioned, but your check engine light is still on? If so, then know that our team of big rig experts here at Kelly’s Truck Repair can help. Come on in or ring us up now so we can diagnose and fix your engine woes.

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