You’re driving down the highway, when you realize that the check engine light is illuminated. Maybe you saw it light up at that very moment, or perhaps it has been illuminated for some time and you’re just now noticing it. Oftentimes, the reason for seeing the check engine light is minor. Regardless, the issue requires an inspection and resolution.

Pinpointing the Cause

There are many different reasons for a check engine light to illuminate, and the list continues to grow as electronics and emissions controls in trucks become more sophisticated. The Electronic Engine Control System functions on fault codes, meaning that the system essentially monitors itself and illuminates the check engine light when it finds a problem. Some fault codes are proprietary to the make of the engine and truck. If either the engine controller or some other module senses something wrong, a specific fault code will trigger the check engine light. These codes make it easier to identify the problem system.

Aftertreatment Issues

One of the most common reasons for seeing the check engine light is the aftertreatment system. Diesel trucks have a nitrogen oxide (NOx) sensors, similar to the oxygen sensors in a car. Before the catalyst, the NOx sensor measures parts per million of NOx being produced by the engine. To ensure the catalyst is performing properly, the NOx sensor compares the reading taken after the catalyst. If the engine does not see a sufficient change in NOx ppms, it will set a code for NOx efficiency. This will cause the engine light to illuminate and the engine will eventually reduce engine power until the problem is resolved.

In 2007, the United States Environmental Protection Agency (US EPA) regulations caused engine manufacturers to add diesel particulate filters (DPFs) to its aftertreatment standards. In 2011, more changes in regulations prompted engine manufacturers to add diesel exhaust fluid to lower NOx levels. These regulations have made engine electronics and engine management more complex, which means more things can go wrong. In turn, the chances of seeing the check engine light are inherently higher.

Passive DPF Regeneration

DPF cleaning or regeneration normally happens when you are driving under certain conditions. If you are driving on a highway at a specified load, vehicle speed and the soot levels or pressure differential across your filter are high, fuel will be injected into the exhaust to clean help burn out the soot collected by the particulate filter. While this helps to burn the particulate being gathered, it can also raise exhaust temperatures and trigger a different light in newer models. Don’t confuse a high exhaust systems temperature (HEST) light with the check engine light; the former simply tells you that a regen is occurring and the exhaust temperature is high. Manufacturers want you to know this out of an abundance of caution, so you avoid fire and heat hazards (such as parking on a pile of leaves or next to a car with a plastic bumper). Nevertheless, if you do see the check engine light come on, it is possible that a problem with fuel injection or engine air management can also be a potential factor.

Don’t Ignore It

The check engine light is rarely an urgency, but always requires attention. If you see it illuminated in your truck or bus, visit the repair specialists at On-Site Fleet Service. With four locations throughout New Jersey, we’re always nearby when you’re driving the Garden State roads and highways. Click here to learn more about our services.

The check engine light in a truck has become much less mysterious than it used to be. What was once a single light with little to no accompanying information might now be three or four different lights with sophisticated displays hinting to where an issue in the engine is occurring. If you notice that your check engine light is illuminated, we recommend taking the following steps:

1. Read Fault Codes

Fault codes are populated by the engine control module when it receives data from sensors that is incorrect, missing, or out of the normal range. This then triggers the check engine light to illuminate. Every model of truck or bus will have its own unique fault codes; some makes of trucks have displays which can give further information as to what component or system is causing the faulty code, while others are more difficult to decipher. A quick Google search can sometimes give you some further information. If you are not sure as to what can be causing your light to illuminate the best decision is to gather as much information as possible as to what is happening and call a qualified truck repair expert for help and a suggestion of how to proceed.

2. Determine Urgency

A check engine light might illuminate due to low fluid, in which case you can simply add coolant or water and continue driving for a short period of time until you are able to see a repair specialist. However, if you see from the fault code that the truck is overheating, this is a rather urgent issue more likely to require roadside assistance or towing depending on the cause of the overheat. Fault codes exist to help determine what engine system or components the problem might be. There are many different possibilities as to why a check engine light will illuminate. Some can be a simple repair as a coolant leak or a broken belt causing an overheat while some require extensive diagnostics and testing to determine the cause of the fault code.

3. Get to the Shop

It can be tempting to continue driving with the check engine light on, especially if you don’t feel any difference in how the engine is running. If you do keep driving for an extended period of time, you could be at risk of the engine derating, which means the engine will eventually reduce power and you will not be able to drive at a normal speed. Some engines will even shut down completely.

To prevent any further engine damage and to avoid going into derate mode, always bring your truck into a repair shop as soon as you see the check engine light illuminated. At On-Site, we can quickly and easily hook your truck up to diagnostic computers to determine what’s going on, fix the issue, and get you back on the road. Visit any of our four locations in New Jersey – we’re open until midnight to minimize your downtime!