Service Engine Light - Real or calculated?

[uriah1]

Does the light for "service engine" come on based on mileage
(I hit 73333) or actual issues, or, both??

[telleutelleme]

In most cars both. In the case of a real need you should get a specific message, light or code. Many auto parts stores can read the codes and if it is just a "service reminder", they can reset it. I take my truck to AutoZone which is near my home and they can reset it. The most common one I've had is the clogged gas cap vent which triggers a warning. Sometimes it needs replacing or sometimes a good smack.

[Joe-Bob]

It depends on how old the car is. However, they are no longer used as service reminders...there is now a separate service reminder.

The trick is to not just read the codes and start throwing parts at it. The codes need to be confirmed and diagnosed. A "trouble code" is not always an indication that a certain part is bad, but rather that something in that circuit is not within the range that the computer expects. The computer cannot distinguish between a root cause or a symptom.

[brewwagon]

the on board computer could be holding fault codes and needs to be read
the check engine light should always come on when you turn the key to start the motor then go out if everythings ok some cars do have a special "service" light for oil changes or a tune up is due
the mechanic will clear the light after the work is done ( unhooks the battery for 15 mins and the computer reboots or there is a switch under the dash)


could be something simple like the gas cap is loose vacuum leak a bad connection or the 02 sensor has gone bad your gas mileage drops the car is running poorly

you need the check the brakes for normal wear service the fluids and rad stuff like hoses and belts

[uriah1]

Originally Posted by Joe-Bob

It depends on how old the car is. However, they are no longer used as service reminders...there is now a separate service reminder.

The trick is to not just read the codes and start throwing parts at it. The codes need to be confirmed and diagnosed. A "trouble code" is not always an indication that a certain part is bad, but rather that something in that circuit is not within the range that the computer expects. The computer cannot distinguish between a root cause or a symptom.

1999

[blowtorch]

yeah i gotta 96 olds with like 189,000 miles on it and my light just came on a couple weeks ago and I can't find any cause, although i'm no one's mechainic . i'm considering resetting it myself (disconnecting the battery ) or maybe just putting some electrician's tape over it, that way i dont have to figure out how to set the clock again, heh

[Big John Studd]

In my wife's van (2011 Toyota Sienna) the "service engine" comes on at mileage intervals. It can be reset by some cryptic sequence like holding down the trip odometer reset button while turning the key on and off. I can never remember the exact steps, but it is explained in the owner's manual.

[BobbyZ]

Electric tape will cover those pesky lights.

Those stupid trouble codes don't always tell you what's wrong. After spending a ton of money on a 99 Chevy pickup it turned out the mass airflow censer was dirty. I had the dealership read the codes on the dammed thing and replaced the parts they said were bad. (dealership machanics make money on every part they sell)

Anyway is your car running ok now?

[uriah1]

Oh...yea..works great.came on during trip to work when I hit 73333 exactly. Odd number

Yea...maybe tape!!

[BobbyZ]

It's a 99 and you only have 73,333 miles on it ? Might be a good idea to find someone to read the codes. Just don't go throwing parts at it like I did !
The code readers are cheap enough now that you may have a friend with one. I think even Walmart sells them now. Or like already stated maybe a parts house would do it for you.

[Daddy Hojo]

My wife's check engine light came on the day after she made the last payment.

[Jack FFR1846]

In most cars, the cel will blink while the fault is occuring and stay on indicating that the fault is stored, but not going on right now. Earlier cars (my 91 honda crx, for example) have the cel come on when the fault is occuring only. After that, you can lift the passenger side carpet on the floor and see the LED blinking to send the code. Count the number of times it blinks and google the code.

Newer cars are still easy enough to get the code. Most big auto parts chains (Auto zone for sure) will read the code for you and tell you what it is. They usually tell me what they think it might be, but at least you know what it is.

If you don't feel anything wrong, you can unscrew the gas cap and put it back on till it clicks. I've had plenty of times where that's fixed the problem.

[flyingbanana]

Originally Posted by Jack FFR1846

In most cars, the cel will blink while the fault is occuring and stay on indicating that the fault is stored, but not going on right now. Earlier cars (my 91 honda crx, for example) have the cel come on when the fault is occuring only. After that, you can lift the passenger side carpet on the floor and see the LED blinking to send the code. Count the number of times it blinks and google the code.

Newer cars are still easy enough to get the code. Most big auto parts chains (Auto zone for sure) will read the code for you and tell you what it is. They usually tell me what they think it might be, but at least you know what it is.

If you don't feel anything wrong, you can unscrew the gas cap and put it back on till it clicks. I've had plenty of times where that's fixed the problem.

Not in California any more....

[emu!]

Originally Posted by Daddy Hojo

My wife's check engine light came on the day after she made the last payment.

I wish my wife had a check anger light...that way, I would know to stear clear of her on a bad day.

[KokoTele]

You need one of these:

http://www.amazon.com/Autel-MaxiScan...obd+ii+scanner



It's the cheapest one I've found and just reports a code, which you then look up to turn into text. (i.e. P0130 is an O2 sensor malfunction)

It will also reset the codes so your CEL goes off. Joe-Bob is right that you shouldn't just throw parts at a code (though that is the solution to the most common ones), but most shops do that anyway. If you're handy you can save some money.

[Joe-Bob]

Originally Posted by KokoTele

It's the cheapest one I've found and just reports a code, which you then look up to turn into text. (i.e. P0130 is an O2 sensor malfunction)

That particular code is also probably the most common one. It also happens to be the one that is almost always a symptom and not the cause.

You should not fix first!

The sensors are easily tested.

All that sensor does is measure the exhaust gasses: if the engine isn't running right, (for any number of reasons), the exhaust will be outside of the normal range--and set off that code.

This is why those codes should not be used as a substitute for actual diagnosis and testing.

[smitty54017]

Get the code and then Google the code and your vehicle type. You'll learn a lot and may save some $$. As mentioned before, a loose or faulty gas cap can throw codes for the EGR, etc.

[Frodebro]

Originally Posted by Joe-Bob

That particular code is also probably the most common one. It also happens to be the one that is almost always a symptom and not the cause.

You should not fix first!

The sensors are easily tested.

All that sensor does is measure the exhaust gasses: if the engine isn't running right, (for any number of reasons), the exhaust will be outside of the normal range--and set off that code.

This is why those codes should not be used as a substitute for actual diagnosis and testing.

Exactly. There are a bunch of sensors in the engine, and all the light does is tell you that one of those sensors is showing a reading outside of its normal operating range. In some cases, the sensor has gone bad and needs replacing. Other times, the sensor is working properly and something upstream of it is out of whack and causing the errant reading.

[sacizob]

Check engine light comes on, put a small piece of black tape over it.

[Nick JD]

Originally Posted by sacizob

Check engine light comes on, put a small piece of black tape over it.

My last car's check engine light came on, so I bridged the gap to get the codes for what was wrong and got code 447: take old car into the wrecking yard and exchange for $350.