Check Engine Light On? – See the First Step

Check Engine Light On
Check Engine Light
Check Engine Light

Everyone knows the car’s main computer turns the check engine light on. However, most motorists don’t know the first step in handling this issue properly. Furthermore, what do professional technicians see as the clear first step when the check engine light pops on? We’ll cover all this and more in this brief article. Instead of forcing you to read the entire article, I’ll tell you what the first step is right now.

Of course, those who read the entire article will benefit from the information on how to best handle a situation where the computer turns the check engine light on. The first steps become recording the codes set in the computer’s memory and then clear those codes. This is the first step that factory trained technicians deploy on the automobiles they work on with a check engine light complaint.

Many do-it-yourself mechanics say they don’t want to purchase an automotive scan tool to perform this procedure. In the following sections we’ll explain how you can clear the check engine light without a scan tool. And if you’re one of those people who think they would be better off putting a piece of tape over the light or disconnecting it, I have an article especially for you. See why you don’t want to disconnect the check engine light on your automobile.

First Step of Check Engine Light Diagnosis

Auto Facts Repair Manuals
Auto Facts Repair Manuals

As a factory trained technician I can tell you that the first step is the most important. Let me rephrase it so that we can further explain it. The first step in diagnosing this problem becomes to physically document the codes and then erase them from the memory. I’m talking about writing them down on a separate piece of paper. Of course professional technicians record this on the back of the repair order.

Let me tell you the reason this step is so important. Because we want to know what codes have set in the computer’s memory. The second half of the first step is to clear these codes because check engine light problems often become intermittent issues. So let’s clear the codes and operate the vehicle for several drive cycles to see if it’s a hard failure or not. When something is broken for good, we call it a hard failure. As an example, if a throttle position sensor malfunctions, after clearing this code from the memory it returns within the first drive cycle.

When you document and then clear the codes you can then focus on the diagnostic trouble codes that return first. This remains important to point out, because additional codes can set due to the root cause of the issue. Generally speaking when discussing check engine light diagnosis you want to start with the lowest code set and then progress to the higher codes. A better method becomes to clear them and address the codes that return first.

Pulling Diagnostic Trouble Codes the Cheap Way

Car Code Reader Tool
Car Code Reader Tool

We’ve all heard the radio and TV commercials talking about how the local auto parts franchise store will pull your trouble codes for free. Some repair shops jumped on this bandwagon, because it’s good for bringing in new customers. Here’s the problem with this free service. They don’t want to clear the codes after you write them down. Some state laws, even prohibit the repair center or parts store from clearing the codes.

You can learn more about this subject in the article we wrote about free check engine light service. The reason people go to the parts store or retail auto center looking for this free service is because they don’t own a scan tool. Prices for the automotive scan tool crashed thanks to heavy competition from foreign suppliers. However, you really don’t need an automotive scan tool just to pull and clear codes. A code reader can perform that task for a price tag under $20 if you shop around.

With the sensitivity built into these check engine light emission systems this becomes a fantastic tool to have around. Thinking that you’ll only use it once and that it’s not worth owning isn’t a valid train of thought. The other solid reason for purchasing a check engine light code reader becomes the amount of vehicles the tool works on. Back in the old days scanners would only work for a couple of model years. With the invention of OBD II or on board diagnostics, these inexpensive code readers work on vehicles from 1996 to present day. That’s a giant amount of automobiles to connect your code reader to.

Clearing Codes without a Scan Tool

Automotive Car Battery
Automotive Car Battery

On automobiles built prior to 1996 all you had to do was disconnect the battery for more than 10 seconds and boom, the check engine light cleared. This made resetting the check engine light far too easy. Car manufacturers implemented a way of storing these codes through a power disconnection event. In other words, disconnecting the battery doesn’t work anymore. The reason for this is, the manufacturer stores electrical energy in a capacitor.

This capacitor continues to feed the memory to keep it alive even when there’s no battery power. It’s possible to circumvent this feature by draining that capacitor. You can do so by activating a circuit with power at all times. The emergency hazard lights or the car’s horn become two good examples of circuits that operate without the ignition keys. Unfortunately, there are a few downsides to using this procedure. Thankfully, we have written an excellent article that covers how to clear codes without a scan tool.

Although clearing the codes without a scanner and seeing if the computer turns the check engine light on again remains better than nothing, it misses a vital step we discussed in the beginning. You really want to know what code set in the vehicle’s computer memory. If you disconnect the battery and defeat the stay alive memory system, you will never know what code set originally. Without that baseline you’ve made diagnosing check engine light problems more difficult.

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