Check Engine Light

there is no reset button, it must be done with an obd2 code scanner ^^ that will probably cost money, easiest way to reset is to disconnect the battery for 15-20 minutes...reconnect and your codes are now lost (which is good) unless of course you do have a problem. In which you light will come back in about a day anyway... The MIL trips are it fails a 'routine.' Some routines take longer to complete than others... that is, you have to perform some common driving maneuvers, other routines run every time you start the car. These same routines can also clear the MIL, if they run without failing 3 times or so. So you don't always have to clear the DTC codes with the OBDII scanner or power loss (disconnect battery), sometimes they clear themselves.

Disconnect the POSITIVE battery cable and touch it to the negative terminal OR disconnect the POSITIVE battery cable for about 30 minutes (either way drains the capacitors in the electrical system)

It is a very broad answer for why your engine light is on. He is probably right that is on due to the oxygen sensor but as for the gas mileage statement. If you haven't changed your pcv valve, that can kill your mileage as well, but it won't cause your engine light to come on. If you are experiencing hesistation in your acceleration, it may be a bad mass air flow sensor and that will cause your engine light to come on and kill gas mileage. I personally have run my vehicle with a bad 02 sensor and passed my state emissions test. So kudos to me. But I also use Slick 50 High Mileage Fuel System Cleaner. This stuff made the engine light go off after a full tank of gas with it mixed in. It cleaned the intake manifolds well enough to deactivate the check engine light. So if you want to put off a potentially couple hundred dollar repair, try the product first. I recommend anyone with an oxygen sensor engine light try this before replacement. It works. I have used it first had on my 2002 Dodge Dakota 4.7L V8. Good Luck, oh, it costs about 8-10 bucks for that slick 50 stuff, worth it though.

Which engine light? I will assume you are referring to the Check Engine light. If so, it means the computer has detected a problem that is effecting the emissions controls. It can be a simple as a loose gas cap, or as serious as a clogged catalytic converter. Have the computer codes scanned and this will give you an idea of where to start. if you turn your ignition on off on off and on again and count the blinks it will blink pause than blink again ex(blink pause blink blink) would be fault code 12 and you can exces the codes meanings over internet or repair manual If you are OBD1 you can count the number of blinks and reference them by codes. If you're OBD2, there is a code reader you can rent (have someone with you to drive around to where you can read it when it throws a code -check engine could be on entire time and still throw codes-)then look code up; as previous answers stated, just didn't state with method was for what OBD. As first answer said, anything simple: fouled spark plug, ect.

sometimes when you disconnect the battery for an hour or two,then reconnect the battery it will reset itself good luck.

To reset a Service Engine Soon light, a person can disconnect and reconnect the battery. They can also fix the problem and use a scanner to clear the codes causing the light to come on.

It depends on the engine:- SOHC Cylinder head underneath the ignition coil. DOHC Cylinder Head under underneath the intake nanifold

Disconnect one post of the battery. If the light comes back on after you re-hook the battery terminal and start the car, get a manual for your car from someone like Amazon. Different brands of cars used different methods of triggering and resetting the lite. The book will be a lot cheaper than a mechanic.

tighten your gas cap, then leave the battery cables off over night and it should clear right up. if not, then your 02 sensors are bad......again. they go bad all the time. i bypassed mine with a sensor cause i live in the humid south and my ram runs lean because of this. if you live where it is cold then you maybe running rich. if an 02 sensor is off by.2% then it will cause a fault. correct air/fuel ratio is 14.1% and its nearly impossible to tune a fuel injection motor to those specs thus causing the 02 sensor to default

The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to AutoZone or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.

I took my jimmy to a transmission shop, they diagnosed it and said the transmission was fine, but that an electronic piece that was some kind of cap was bad and it caused the tranny to not shift properly. I cannot remember the name of the part, I know that i looked it up right after that and found it in the repair manual, and it looked almost like a distributor but with an electronic module and several wires. Now a year later I want to actually fix mine and cannot remember what the part was...

A flashing check engine light means that an engine cylinder misfire has been

detected . You will need to have the vehicle scanned for any trouble codes

to help diagnose and then repair the problem . You can drive the vehicle in for

repair , just avoid any rapid acceleration or deceleration because you can

damage the catalytic converter

That is usually an indication of a misfire. You need to have the codes checked, and you can then diagnose the indicated cylinder.

see related questions below.

Have an auto parts store do It for free or pull the battery and let sit for 10 minutes (will need radio code after and reprogram seats, presets)

The check engine light comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to AutoZone or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.

Trouble code P0304 means:Cylinder 4 misfire detected

You usually get this indication when it's time for a tune up - oil change, air / oil filter change - routine things. Most cars that give this kind of indication have a mileage counter of some sort and as you approach the max mileage it's set for, it starts letting you know it's time for maintenance.

P0300 Diagnostic Code - Random Misfire

Symptoms.
Engine may stumble or miss
Engine may be hard to start
you may notice no issues

Cause
Failing spark plugs or spark plug wires
Bad coil or coil pack
Failing oxygen sensor(s)
Bad fuel injector or more than one
Stuck exhaust valve
Bad catalytic converter
EGR valve or valve passage clogging
Bad camshaft position sensor
Bad PCM or ECM

The Fix
Best first action is a tune up, new plugs, wires, inspect all hoses and wire connections then reset the code. If it returns you will need to narrow it down to a system, coils and coil packs should be tested, catalytic converters for function ( do you smell rotten eggs?). A misfire that jumps cylinders could indicate a lean condition, do you have any other codes along with the 300? this will help clue you in to the source, check valve function to make sure they are opening and closing fully.
This is probably pone of the most difficult codes to troubleshoot, so start with the basics and work your way into the more expensive options, in many cases a good old tune up solves the problem, back it up with a fuel system cleaning and see where you stand.

It means that there is a failure in the vehicle that will affect emissions.

likely an emission system problem. or bad oxygen sensor, thereby making the engine run rich, putting too much gas into the engine that doesn't get burnt off so you smell it either slightly flooded in the engine, or most likely out of the exhaust (where most of the gas goes without being burnt anyway thanks to government regulation of cars which they have no understanding of combustion.)

Trouble code P0603 means:Internal control module keep alive memory (KAM) error

need special tool, or go to dealer

The inspection light indicates the need for an oil change or other part of the BMW maintenance schedule. The light needs to be reset when the maintenance required has been performed. This can be accomplished by jumping certain holes in the diagnostic plug in your engine compartment depending on the year. If you message me the year and model I can send you the proper diagram and instructions.

There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.

You may be able to reset it after you repair the problem that set the light in the first place, by disconnecting the battery for 5 minutes. That may not work on your 1996. If not, you will need an OBD scan tool to reset the light.