Reader Question: The Dread Light?

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Here’s the latest reader question, along with my reply!

Leiann asks: Why does the Check Engine light remain lit? I have had various diagnosis, the latest being a solenoid not available, still on order. Otherwise, truck – an ’01 Tacoma – runs great with 145,000 miles original owner.

My reply:  Your truck – like almost all vehicles made since the mid-’90s – has OnBoard Diagnostics II (OBD II) which includes a universal language of “codes” that can be used to  . . . diagnose what ails the engine and call the driver’s attention to the existence of a problem that might otherwise go undiagnosed..

When the “check engine” light illuminates, it means the OBD system has registered a fault and thrown a code.  This triggers the “check engine” light, which is meant to alert you to the code having been thrown and to have the code (and so, the problem) identified, via plugging in a code reader to download and translate the code.

If you look under the steering wheel area, you will see a universal port – which works very much like the USB ports for handheld devices. The technician – or you, if you have a code reader – plugs in the code reader and reads the codes, which tell him (or you) what the issue is.

The code can then be cleared – and the “check engine” light goes off.

When the light comes on, it is usually because of an issue with the emissions system and thus not generally an issue in terms of how the engine runs; however, the problem could lead to the engine not running well and for that reason it’s a good idea to find out why the system threw a code and then get whatever caused that to happen fixed.

It might be something as trivial as the gas cap not having been tightened properly.

. . . 

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  1. Back in 2014 after purchasing my GM Holden, the check engine light came on. I also noticed that the tranny was shifting oddly. I also was informed the fluid was changed shortly b4 I purchased the car. I checked the fluid which was low, added some atf and the light went off.

  2. The work truck, a 2011 F-150 with 375,000 miles on the odometer, has started to show its age. The current issue is that the fuel gage isn’t showing the actual fuel level. It also is showing an intermittent check light, my assumption is for the gas cap since it sometimes clears after a fill up. My guess is there’s a loose ground causing both issues, but haven’t had time to get it into the shop.

    • Your gas cap has a rubber gasket around it. That gasket can leak over time and cause the problems you see. Start with that b4 going to the shop.


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