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That is not the purpose of the check engine light (official name "Malfunction Indicator Light"). At least in the US the light only comes on when there is a pro

That is not the purpose of the check engine light (official name "Malfunction Indicator Light"). At least in the US the light only comes on when there is a problem that affects emissions, and it is usually nothing that would cause a breakdown. It usually does not mean anything serious is wrong and the most common cause is a loose gas cap, which is easily fixed.

tsomctl 12y ago
A check engine light most definitely can tell you that you are about to have a breakdown. It's original and most common purpose is emissions control, but it has been extended. An overheating engine will cause the check engine light to come on (happened to me last week in an 88 4Runner) and this has nothing directly to do with emissions. Blow a head gasket, and there could be a long list of repairs besides a new gasket. And even if it is a problem that primarily affects emissions, it might still have a bigger problem. A bad O2 sensor can cause your engine to enter open loop and run rich, meaning that you're blowing gasoline out your tail pipe, costing you money. A misfire can cause the light to come on (bad spark plugs, compression leak, bad fuel injector, bad timing, bad lots of things) and can cause reduced power (which might not be noticeable in city driving), burnt valves, and again blowing gasoline out your tail pipe. Blowing gasoline out your tailpipe will ruin your catalytic converter, which you might not care about right now, but will matter if you try to smog your vehicle to sell it. I've had the check engine come on in a number of vehicles I've worked on, and it has always been a more serious problem than a loose gas cap. The previous owner of the above mentioned 4Runner ignored her check engine light. By the time I got to it, the engine, 02 sensor, and catalytic converter were destroyed. If your check engine light is on, scan the codes and make sure that it isn't anything serious.
joshmlewis 12y ago
Yeah to second what the other poster said, it can indeed mean a lot of different things. Sometimes it is as simple as an emissions error but sometimes, especially if you ever see it flashing, that means there's something bad wrong going on with the engine itself. It could be anything from a knock or misfire in the engine to sensor failure. It's always wise to get it checked (a lot of auto parts stores do it for free) or just buy a cheap but good obd-2 tool and that will tell you the code and you can go Google and research from there.
pbreit 12y ago
This is obviously wrong. The check engine light, even on US cars, can indicate a variety of problems unrelated to emissions, some serious.

tsomctl 12y ago

A check engine light most definitely can tell you that you are about to have a breakdown. It's original and most common purpose is emissions control, but it has been extended. An overheating engine will cause the check engine light to come on (happened to me last week in an 88 4Runner) and this has nothing directly to do with emissions. Blow a head gasket, and there could be a long list of repairs besides a new gasket. And even if it is a problem that primarily affects emissions, it might still have a bigger problem. A bad O2 sensor can cause your engine to enter open loop and run rich, meaning that you're blowing gasoline out your tail pipe, costing you money. A misfire can cause the light to come on (bad spark plugs, compression leak, bad fuel injector, bad timing, bad lots of things) and can cause reduced power (which might not be noticeable in city driving), burnt valves, and again blowing gasoline out your tail pipe. Blowing gasoline out your tailpipe will ruin your catalytic converter, which you might not care about right now, but will matter if you try to smog your vehicle to sell it. I've had the check engine come on in a number of vehicles I've worked on, and it has always been a more serious problem than a loose gas cap. The previous owner of the above mentioned 4Runner ignored her check engine light. By the time I got to it, the engine, 02 sensor, and catalytic converter were destroyed. If your check engine light is on, scan the codes and make sure that it isn't anything serious.

joshmlewis 12y ago

Yeah to second what the other poster said, it can indeed mean a lot of different things. Sometimes it is as simple as an emissions error but sometimes, especially if you ever see it flashing, that means there's something bad wrong going on with the engine itself. It could be anything from a knock or misfire in the engine to sensor failure. It's always wise to get it checked (a lot of auto parts stores do it for free) or just buy a cheap but good obd-2 tool and that will tell you the code and you can go Google and research from there.

pbreit 12y ago

This is obviously wrong. The check engine light, even on US cars, can indicate a variety of problems unrelated to emissions, some serious.