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Historical Data vs. Present Alerts: Tracking Your ‘Service Engine Soon’ Light Over Time

BY: David Rabin
A woman having car trouble and calling a tow truck on her cell phone

Seeing a ‘service engine soon’ light on your car’s dashboard is never comforting. Car owners who experience this for the first time are likely to ask, “What does this mean?” while those with a more troublesome vehicle are likely to think, “What’s wrong now?” or “How much is this going to cost me?” These are all natural reactions.

⁤Dealing with the problem at hand is always the priority, but keeping track of check engine lights provides valuable insights and long-term benefits. ⁤⁤It’s a simple way to monitor your car’s health, spot frequent issues, and stay informed to make better maintenance and repair decisions. ⁤

⁤Keep reading as we explore what’s involved in observing your car’s history of trouble signals and explain the most common reasons service engine soon lights come on. ⁤

Understanding the ‘Service Engine Soon’ Light

Let’s first review what ‘service engine soon’ and ‘check engine’ lights mean. Simply put, they’re an early warning sign that something isn’t right with your car. It’s no different from when a raised body temperature or first sniffle reveals that an illness is approaching. In the case of your vehicle, these warning lights mean that the onboard diagnostic system has detected an issue that needs attention.

These alerts are often for something simple like a loose gas cap or a disconnected hose. However, these lights can also indicate more serious issues, like engine misfires or a faulty catalytic converter.

These sophisticated warning lights are relatively new in the automotive world. More basic “idiot lights” first appeared in the 1930s, but these didn’t trigger until something serious (like high engine temperature) occurred. There were no advance notices of problems ahead. If one of these lights went off, your car was already in trouble.

The 1970s saw the rise of car pollution control systems, followed by rudimentary technology in the early 1980s to monitor these components. These first-generation onboard diagnostic (OBD) systems (known as OBD I) were proprietary car computers for each automaker, causing confusion among independent mechanics and DIY car owners.

This all changed in 1996 with the introduction of OBD II (or OBD2), a standardized system for vehicle diagnostics. Since then, every car sold in the U.S. has been required to have this universal way of monitoring and diagnosing problems. These OBD II mandates require a universal interface (the port is usually under the dashboard) and standardized trouble codes (there are thousands). Professional auto technicians, amateur mechanics, and ordinary car owners all work off the same playbook.

For example, P0420, a diagnostic trouble code (DTC) for a malfunctioning catalytic converter, light means the same thing in a Ford as it does in a Honda. However, some automakers have added codes to help the diagnostic process.

OBD II continuously monitors a wide range of components and systems, such as the engine, transmission, emissions controls, and numerous sensors. If it’s electronic and related to vehicle operations, the OBD II system is likely monitoring it.

When a problem is detected, the system logs a DTC and illuminates the service engine soon or the check engine light on to warn you. Unlike the idiot light or OBD I days, there’s less guessing about the issue. DTCs help technicians pinpoint the problem, which speeds up repairs and minimizes costs.

Significantly, the service engine soon light and the check engine light (CEL) differ from a ‘maintenance required’ or ‘service due’ light. The latter are maintenance reminders for an oil change or other standard service. In contrast, a service engine soon light is an alert that the OBD II system has detected a problem that should be promptly addressed to prevent potential damage or safety issues.

The Importance of Historical Data

With the essentials of check engine lights explained, let’s review how the importance of historical data comes into play. Yes, it’s only natural to focus on the immediate when a warning light occurs, but stepping back for a broader look at your car’s troubles can save time and money.

Parents keep track of their children’s medical history, as do people with chronic health conditions. Similarly, wise car owners keep a record of not only repairs but also diagnostic trouble codes. By logging each incident of a service engine soon light and the meaning behind it (the DTC), you can start to identify patterns or recurring issues.

A typical driver will see a check engine light, drop the car off at the mechanic, and pick it up after repairs are complete. Not much thought goes into what triggered the CEL. After all, out of sight, out of mind is how most people approach modern life.

However, being mindful of service engine soon lights and the resulting DTCs over the long term can make a difference. Let’s go back to the faulty catalytic converter example. At some point, every car needs one replaced—these components don’t last forever. However, a bad catalytic converter can be caused by more than age. Sometimes, all it takes is a faulty oxygen sensor or spark plug.

Another example involves engine misfires, which can cause improperly combusted gasoline to enter the converter, deteriorating the sensitive internal components. The general DTC for an engine misfire is P0300 (random or multiple misfires detected). Cylinder-specific codes (P0301-P0308) can also be present.

Let’s envision a scenario where you’ve previously tracked a P0300 misfire code before replacing a catalytic converter. A year or two later, P0300 appeared again. Having historical data can alert you that you might be on the path to another catalytic converter replacement, which isn’t cheap.

Beyond specific issues, tracking DTC history provides an overall picture of your vehicle’s operating condition. More frequent appearances of a CEL can be a sign that there’s a greater problem waiting ahead. Yet frequency can be a matter of perception. You may think the check engine light only pops on every couple of months, but keeping a log can confirm these beliefs or show that it’s more like every few weeks (an even larger red flag).

Present Alerts and Immediate Actions

Eventually, every car owner experiences a check engine light. There’s no need to worry. The first step is to assess the situation. Is there a change in performance, like reduced power or sluggishness? Are there any vibrations, unusual sounds, or smells? Play it safe if there’s a significant change in how the car operates or the CEL is flashing. You should pull over (where it’s safe), turn off the engine, and call for roadside assistance.

There are also some basic steps to take in non-urgent situations:

  • Check that the fuel cap is on tight.
  • Park and turn off the car. Restart the engine and continue driving to see if the service engine soon light goes away.
  • Use an OBD II reader (discussed below) to identify the trouble code.

You may also encounter a CEL that comes on momentarily and then goes away on its own. This isn’t unusual, but don’t automatically breathe a sigh of relief. Note what happened (including under what conditions) and be alert for a repeat appearance of the warning. The OBD II system might have detected an intermittent issue that requires investigation.

Even if the issue appears minor (or the error code goes away), it’s always a good idea to get a professional opinion. Minor issues can turn into major (and expensive) problems. A qualified and trusted mechanic has the expertise and comprehensive diagnostic tools to identify the trouble and recommend appropriate action. This is also an excellent time to share your observations and any log information you’ve recorded. It’s information that can spot patterns or recurring issues.

Extended Warranty Considerations

Outside of simple fixes like tightening a gas cap or reconnecting a hose, auto repairs today aren’t cheap. And this work is getting more expensive. A recent CNBC report cites rising labor costs, which have increased by 20% since 2019, as a significant factor. Further, replacement parts are as much as 17% more expensive than two years ago. Overall, vehicle repair costs have increased by 10% annually since 2022.

Extended car warranties protect against surprise repair bills and offer a hedge against inflation. For instance, auto protection plans from Endurance Warranty have locked-in premiums, regardless of how expensive service work gets and what problem is associated with a service engine soon light.

An extended warranty (also known as a vehicle service contract) essentially takes over when the original factory warranty expires. Car owners can choose from primary coverage for the powertrain (the engine, transmission, and drive axle) or a program closer to the manufacturer’s bumper-to-bumper warranty. There are in-between options that balance protection and cost.

Where you get a car serviced also matters—a mechanic has to know how to translate a diagnostic trouble code into an actionable repair. Endurance customers can select an ASE Certified mechanic or repair shop for covered repairs, ensuring convenience and quality work. It all adds to peace of mind, something that’s not usually associated with a car’s check engine light.

Integrating Historical Data for Long-Term Car Care

Capturing the check engine light history and other information doesn’t have to be complex or time-consuming. A few tools and practices will enable you to stay on top of your vehicle’s health easily.

Read the Fault Codes

Start with an OBD II code reader or a diagnostic smartphone app. These connect to your car via the OBD II port under the dashboard. The code reader or scan tool plugs in via a cable, while the app uses a Bluetooth-equipped plug-in sensor. These are as basic or as complex as you want them to be. At a minimum, you’ll be able to get a readout of most diagnostic trouble codes. Meanwhile, some apps supplement the DTC information with plain-language descriptions of the problem, typical repairs, and cost estimates. $20 to $50 is all that’s required. However, more expensive devices provide technician-level information, which isn’t much use to the average car owner.

Take Notes

Next, you’ll want to capture all the details about DTCs, trouble symptoms, car conditions, and other factors that can help spot recurring vehicle issues. Although a bit old-school, you only need a small notebook that can be stored in the center console or glovebox. If paper isn’t your thing, use a note-taking app.

Keep Records

Keeping copies of service records and repair receipts can be invaluable. Not only can you confirm what work has been done, but you’ll also know how much you’ve spent keeping your car on the road. This information is vital to help you decide about future repairs and your car’s long-term reliability.

The right information in hand (a DTC history, vehicle log, and repair records) and regular maintenance can lead to fewer headaches, lower repair costs, and improved vehicle longevity.

Freedom from Check Engine Light Worries

One way to lessen the worry about your service engine soon light on or check engine light is to protect your vehicle with an Endurance auto protection plan. Find out more by requesting a FREE quote or visiting our online store for instant plan and pricing information. Endurance plan advisors can also help. Call (800) 253-8203 for personalized help.

The Endurance blog is also available with topics on car repairs, DIY maintenance, vehicle repairs, warranty advice, and more.

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