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30 March 2010 @ 11:01 pm
Question for the Hive Mind: Auto Motives  
... when the "Service Engine Soon" light comes on, how badly is one's wallet about to get raped?

I feel: disappointedoy!
Braxusbraxus on March 31st, 2010 06:26 am (UTC)
Really depends on what's wrong. If you know someone with an OBD reader, you can hook it up to your car and at least get a diagnostic error code that you can then lookup.
Your Obedient Serpentathelind on March 31st, 2010 06:53 am (UTC)
That's what thoughtsdriftby said.

So where do I go?
Braxusbraxus on March 31st, 2010 06:59 am (UTC)
Oops just realized that I misread the post as a check engine light. A service light usually just a reminder that you should do some routine car maintenance soon (e.g. oil change).

Usually you can reset that notification light fairly easy. Know in some cars like Hondas, you just press and hold down the trip reset button while you turn on the car and that'll reset the counter for the service reminder light for another couple thousand miles.

Edited at 2010-03-31 07:00 am (UTC)
Braxusbraxus on March 31st, 2010 07:11 am (UTC)
If the service light is indeed a check engine light (dunno what you drive), you can usually go to any auto-shop and they'll dig out the codes for you. Or if you're not too far, I have an OBD-II reader that should work with most cars made in around the mid-90s or later.
Curious Coonhalfelf on March 31st, 2010 10:33 am (UTC)
AutoZone (if you have them there) will tell you what that light means for free.
Your Obedient Serpent: YAYathelind on March 31st, 2010 03:19 pm (UTC)
You get a cookie.
Eredieneredien on March 31st, 2010 01:06 pm (UTC)
It's a bit hard to tell. Why not find an honest mechanic in your area?
Your Obedient Serpentathelind on March 31st, 2010 03:20 pm (UTC)
ooh, this should come in handy.
JamesBjames_b on March 31st, 2010 01:42 pm (UTC)
For that very reason, I bought an OBD reader for about 40 bucks.

If your service engine soon light = check engine light, it could be as simple as one spark plug misfiring and in need of replacement, to a faulty oxygen sensor in the exhaust system, to a problem in the transmission. There are a lot of items that will cause the light to come on.
Your Obedient Serpent: coyote drivesathelind on March 31st, 2010 03:34 pm (UTC)
Depending on how much this costs, I may pick one up -- though it's hard to beat AutoZone's Free OBD Check.

According to my manual (a used car that came with the original manual! Amazing!), the "Service Engine Soon" light is indeed the "Check Engine" light.

Modifications made to the engine, transaxle, exhaust or fuel system of your vehicle, or the replacement of the original tires with other than those of the same Tire Performance criteria (TPC) can affect your vehicle's emission controls and may cause the "Service Engine Soon" light to come on.

Obviously, I just changed a tire -- it's the same kind as the other three, but there are differences in wear patterns, and I don't know if they checked and filled the pressure in the old ones, so there might be enough difference there to freak the chip out.

Rewiring the fuel pump might also count as "modifications to the fuel system".
JamesB: Technobabblejames_b on March 31st, 2010 05:52 pm (UTC)
Some times the "check engine" light comes in for seemingly innocent reasons.

One of my cars always brings up the "check engine" light if I fill the gas tank a little too full. It's due to gas tank level affecting the return line to the gas tank, and the engine management detecting the problem.

On another, driving through a puddle that causes water to splash on the spark plugs will cause the light to come on due to a spark plug misfire (or in the case of the code it brought up ... random/multiple cylinder misfire detected - catalyst damaging level of misfire on more than one cylinder).

I've had the light come on showing a transmission fault after the battery went flat and I started the car after insufficient recharge time to fully charge the battery. The system detected that the battery voltage was too low for reliable operation of the auto transmission, and put the transmission in "limp home" mode.
Your Obedient Serpentathelind on March 31st, 2010 06:29 pm (UTC)
The manual listed some similar things, including "puddles messing with electrical system".

I'm gonna open the gas cap and re-seal it, then go check the tire pressure, and see where that leaves me. EVERYTHING, including the manual, suggests that a) It's Nothing Urgent Or Critical and b) It May Just Go Away By Itself In A Few Days, esp. if I do those little things.

Hmmm. The manual mentions that the light might come on if you're low on fuel, as small amounts of air can get into the fuel line and cause a misfire. Sounds like trying to start the engine with a nonfunctioning fuel pump would cause the same effect—though it's odd that it would hit 50 miles later.

Consensus: If it's still shining merrily on Monday, then I'll worry.
JamesBjames_b on March 31st, 2010 06:47 pm (UTC)
You may still need access to an OBD reader to reset the "check engine" light.

While some vehicles will auto reset some of the "check engine" codes if the problem goes away, on many cars, even if the fault condition is no longer there, the "check engine" light will stay on until the end of time unless it is reset with an OBD tool/reader.
Bobyourbob on March 31st, 2010 04:18 pm (UTC)
I know you're about to head out, if you haven't already. First thing you should try is re-seating the gas cap.

I've been told by my mechanic that the check-engine-light can be something as silly as that and usually involves the exhaust system.

And yes, messing with the fuel pump wiring could mean it needs to be reset.

Generally (no promises) it's non-urgent, especially if it's the exhaust system.