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What is my "check engine" light trying to tell me?

 
Trailboss
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My "check engine" light came on two days ago. Although it wasn't due for service yet, I took my rig to the grease monkey and had them do their thing. The check engine light is still on. I replace the air filter. Still on.
I took it to the toyota dealership and they said that they could hook it up to the computer and find out what is making the light come on. But I would have to leave the car with them all day and it would cost a hundred bucks. They also said that one of the things that makes the "check engine" light come on is if you didn't tighten your gas cap enough. They also said that it's probably no big deal to keep driving it. It's when the light flashes that you should stop driving it.
In this day and age, I would think I could drive up to an auto parts store, they would plug something in, tell me what the problem is and charge me twelve bucks. Or, better yet, I could look somewhere and see an LED display that has a nuber on it that I can look up on the internet.
Any suggestions?
 
author and iconoclast
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Your "this day and age" scenario should be true and in fact I understand it will come true soon; but right now much of the code and protocol info is proprietary and the auto mfrs will only sell it to you if you've got the cash. Apparently there are moves afoot in the industry -- and in Congress -- to change this.
As far as what the light means: every time it's ever happened to me it means that one of the myriad sensors in the emission system has croaked and needs to be replaced. Of course, it could mean something else. But with Fords, Saturns, and Subarus, apparently the most likely explanation is just that there's a bad sensor.
It can mean the gas cap was loose, and if so, I've heard it can take you burning through half a tank before the situation clears up on its own. Worth giving that a try.
 
Ranch Hand
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There are guides on the internet on how to make your own interfaces and tables of code meanings. I aint done it myself though because I don't yet have a car.
 
Greenhorn
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i got the same problem on my jeep. the problem started more than 1 year ago. since then i reset fuse, changed battery,.. each time the light went away, but come back later, i also took it to a garage, they can not fix it either. i searched the internet, it looks like this problem is pretty common among all kinds of vehicles. and most people think it is not serious.
several months ago, when i had oil changed, i asked the guy reset the light again. now it works, it never come back again. but then i realized he probablly did something wrong, because my car alarm is not working any more.
[ March 21, 2004: Message edited by: fred snow ]
 
Desperado
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I have never had that problem with my trusty 1987 Toyota Corolla... Oh wait! It has no "intelligence insulting Check Engine" type of signal!
And whenever there's a problem, it's very cheap to fix. It's usually mechanical and not electronic.
The car shop only screws the people with the new, expensive cars. I am protected against that rip-off. The guy told me.
But then again, a car like that is all that I need to drive to work, 1.6 miles away...
 
Ranch Hand
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If there are no other signs of problems, the best approach is to ignore it. Unless, you want to spend a lot of money trying to find out, without any guarantee you will find out.
 
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My father had such a light come on in his Thunderbird last autumn.
After several days of fruitless searching (at no cost, that's Ford Service for you) someone finally thought to check the circuitry that determines whether the light should come on and found it to be in error.
Replace one printed circuit board (free of charge, on a 6 year old car) and no more problems.
 
Ranch Hand
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The light usually comes on because of an emissions problem. it is typically no big deal and is usually caused by the gas cap not being put on properly (happens a lot of you go to full serve gas stations where the employees are too lazy to make sure the cap is on right.) After a tank of gas or so the light should shut off. If after a week or so it does not then there could actually be something in the emission system that needs replacing, but it will not impair your ability to drive the car until you have time to get it fixed.
My Aunt had this problem quite a bit on her Mazda. Drove a good month before getting it fixed.
 
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Autozone claims they will read your code for free. I tried, they could not do it.
My chilton's manual showed a way I could watch lights flash and read the code. It did not work.
Some manufacuter'e have a way to show you via the check engine light. You do something like turn the car on but not start it. Turn it off. Turn it back on but not start it again and it flashes out the code.
While you can ignore it for a while, you should not ignore it forever.
 
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http://neons.org/howtos/diag.shtml

1. Cycle the ignition key ON-OFF-ON-OFF-ON within 5 seconds.
2. Count the number of times the "check engine" lamp on the instrument panel flashes on and off. The number of flashes represents the code. There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate individual codes. For example, flash-flash-flash [pause] flash-flash represents the code 32.
To cycle the ignition key ON means to turn it only as far as it takes to get the radio to come on. It does not mean to turn the
engine on.
CODE Description of Trouble Code
11 Timing belt skipped 1 tooth or more from initial learned value, Intermittent loss of either camshaft or crankshaft position sensor, No crank reference signal detected during engine cranking
12 Direct battery input to PCM was disconnected within the last 50 key-on cycles
13 No change in MAP from start to run
14 MAP sensor voltage too low
15 No vehicle speed sensor signal
17 Closed loop temp not reached or engine cold too long
21 02s sensor problem (oxygen sensor), upstream or down stream
22 Engine coolant temp sensor out of range
23 Intake air temp sensor out of range
24 Throttle Position sensor out of range
25 Idle air control motor circuits, target idle not reached (+/- 200),vacuum leak found
27 Injector control circuit
31 Evap purge flow monitor failure or evap solenoid circuit
32 EGR system failure
33 A/C clutch relay circuit
34 Speed control Solenoid circuits
35 Rad Fan control relay circuit
37 Torque converter clutch solenoid CKT or park/neutral switch failure
41 Generator field not switching properly
42 Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles
43 Multiple/ single cylinder misfire
44 Battery temp sensor volts out of range
46 Charging system voltage too low
51 Fuel system lean
52 Fuel system rich
53 Internal control failure
54 No Cam signal at PCM
55 End of error messages (If you get this only, no errors were found)
62 PCM failure SRI mile not stored
63 PCM Failure EEPROM write denied
64 Catalytic Converter Efficiency Failure
65 Power steering switch failure
[ March 23, 2004: Message edited by: HS Thomas ]
 
fred snow
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the vehicle i am having "check engine" problem with.
[ March 23, 2004: Message edited by: fred snow ]
 
Ranch Hand
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the vehicle i am having "check engine" problem with.
 
paul wheaton
Trailboss
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HS, that's some damn useful info! I shoulda done that before taking it in!
So I took it into the Toyota Dealer in Boulder. The guy said it would be $95 to hook up and see what the computer says. He apologized that I was past warranty. He said Toyota used to be a little lax about some warranty items, but with the economy being down, they've been a little tougher.
So I told him to go ahead and do it.
Turns out that I needed a software upgrade. Everything was fine, but the older version of the software was set to be too sensitive. And sense the sensor that was being too sensitive was in my exhaust system, apparently my exhaust system has a longer warranty, so it was all free!
 
paul wheaton
Trailboss
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So the trick is to find an outfit that has the contraption that is not the dealer!
 
Rufus BugleWeed
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It's ODB, On Board Diagnostics. One can buy an ODB code reader for say $129 to $399 which is probably a rip off. It should be just a simple serial interface to a microcontroller and a display. The real cost probably is in de-hashing the codes for every make model and year of car.
I suspect one should thank the California Air Resources Board (CARB)for the device. Probably it will save zillions of dollars in car repair. I could bore you with propoganda about the Kyoto treaty and how the US is not all bad ...
The trick is finding an honest human being, not intent on having you make a boat payment, to fix your entity. I think that's close to how Tom and Ray put it.
You've just wasted another perfectly good 2 minutes reading MD.
 
HS Thomas
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The vehicle I am having CEL problem with.

I win.
[ March 29, 2004: Message edited by: HS Thomas ]
 
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