Here’s the latest reader question, along with my reply!
Patrick asks: About check engine lights: I have one newer car and two older. With all three there is this check engine light that comes on from time to time. Reading the manual they recommend an immediate stop at your Toyota/Ford/Honda dealer. I would be very grateful to have the perspective from a knowledgeable auto person about how seriously these indicators should be taken. Someone told me it is a problem if the indicator light flashes. Sometimes the light comes on, occasionally it flashes, then it turns off again. There is no perceptible change in the behavior of the engines. All the fluids are fine and the cars are regularly maintained. If I visited a dealer every time a check engine light came on I would be a car dealership gypsy.
My reply: The “check engine” light – or malfunction indicator light (MIL) – generally lights at start-up, then (should) turn off after a few seconds, just like other warning lights in the gauge cluster. If it comes on and stays on, it means the OnBoard Diagnostics (OBD) system has registered a trouble code. The idea is to alert you to the need for service, which might be something very trivial – such as a gas cap that isn’t sealing properly. Or it could be a bad oxygen sensor, or some other issue.
Usually, it’s an emissions control-related issue.
Note that the light is yellow, not red. In other words, it is rarely a critical issue. Unlike, say, the red oil pressure indicator light. Which means – stop the car (and engine) right now!
Yellow lights just tell you to get it looked at when convenient.
Which you should do.
While it isn’t an emergency, running around with a bad oxygen sensor – a relatively cheap part – could over time result in damage to a more expensive part, like a catalytic converter.
First way: Many auto parts stores – Advance Auto, for instance – will check (and clear) trouble codes for free. They can also tell you what the code is – and means – so you’ll have the knowledge, in the event you decide to go to a dealer or mechanic to have whatever the issue is addressed. And it might be that all that needs “fixing” is a loose gas gap – or that you need a new gas cap. The MIL will trigger if the cap hasn’t been tightened properly, or a vapor leak is detected.
Second way: You can check – and clear – the OBD codes yourself. Every OBD-equipped car (since the mid-late ’90s) has a universal port, usually to the left of the steering wheel, under the dash, into which you plug scan tool. These are relatively inexpensive – $100 or so should buy you one that not only reads the codes but tells you what the codes mean – and much less expensive than several trips to the dealer.
Here is an article on this I wrote last year which you may find helpful.
It is very easy to use a scan tool – and a huge time/hassle saver if the MIL came on because of something like a loose or bad gas cap. Just clear the code, tighten (or replace) the gas cap – and you’re all set!
. . .
Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!
If you like what you’ve found here please consider supporting EPautos.
PS: Get an EPautos magnet (pictured below) in return for a $20 or more one-time donation or a $5 or more monthly recurring donation. (Please be sure to tell us you want a sticker – and also, provide an address, so we know where to mail the thing!)
My latest eBook is also available for your favorite price – free! Click here.