Check Engine Light

Forget the fuse. Maintain your engine.

The sole function of the 'check engine' light is not totally restricted to malfunctioning oxygen sensors. There are a myriad of things that can cause this warning indicator to illuminate on the dashboard. When it come on, there is a code number then stored in the computer's memory - requires a special tool to read that code number and then interpret that number into plain language we can understand. The tool is quite expensive ... not what the ordinary DIY home garage wanna be mechanic would buy to use maybe once or twice a year. Places like Autozone will read the codes for a nominal fee. At least, that done, you will know what the problem really is. Shooting from the hip in troubleshooting car problems is not the best solution. Chances are, those oxygen sensors were okay and didn't even need to be replaced. Get it checked out to find out the real problems.

I just bought a 2001 s500. The person I bought it from told me that if I let the gas get too low or did not tighten the gas cap properly, the "check engine" light would come on. Well, about two weeks after I purchased the vehicle I let the gas get a little low and sure enough the "check engine" light came on. I filled it up with gas and the "check engine" light stayed on. I got worried. Finally after two days of being on it just went out by itself. Has not come back on since.

Pull the light knob out - it's two stage, front and rear.

Trouble code P0456 means: EVAP Control System Very Small Leak (0.020") Detected

All below are true, I would lean toward an O2 sensor. Take it to a independent garage and find out what the codes are for the Check engine light. 1 dirty or clogged air filter element. 2 emissions system not functioing properly . 3 fault in fuel or electrical systems . Have a mechanic check the PCV valve and the injectors, they should better tell you the problem. The first response sounds plausible. The EGR may also be at fault. An Independant garage is the right start to diagnosing it. The "Check Engine" light just means that the engine control computer has found a problem, and that you need to check the detailed diagnostic codes (or have your service shop check them). The bad fuel mileage is probably because the engine control computer is running the engine in a "safe mode" because it's no longer getting enough reliable data to run it normally. I had this same problem, fuel mileage dropped from about 35 mpg to about 25 mpg. In my case, the problem was an oxygen sensor, which had to be replaced. (Your specific problem may be different, although the computer's reaction makes the symptoms the same.) I replaced the sensor, the idiot light is now off, and mileage is back to 35 mpg. I've had two Civics, both of which eventually had the same problem (1988 CRX at 150,000 miles, and a 1997 EX 4-door at 90,000). Both times it was the throttle position sensor. You can buy an OBD-1 reader for $30 - used on older cars A OBD-2 reader cost around $200 They sell them at all autoparts stores. Check engine light comes on for an "emission system" problem only. I'll go along with the EGR, or the O2 sensors as a possiblity. And I agree with the "safe mode" interpretation as to why it runs fine now. Bottom line is get it to an independent repair shop that specializes in this, and have them fix it. Pull the codes from the computer, match the code to the troubleshooting procedure, follow the procedure to find the source. Repair the source, light will go out if that was the only problem. There are "monitors" or self tests the computer runs the car through a drive cycle, if a problem occurs, it may not run all of the self tests until that problem is taken care. Therefore, another problem may exist. It is emission related. OR hook up a scanner that is capable of clearing codes, and hope that none are still active. The " check engine light" is by far one of the most misunderstood technological advances by the public. I am sure I will revise this as time goes on, as it is an in-depth understanding for the public. It is a warning light that is illuminated when there is a problem with the EMISSION SYSTEM only. Emission system being the pollution control system. Don't get a hard on against it as it is a good thing once you understand it. One point that was brought up a a recent meeting of technicians was that the amount of hydrocarbons is greater when the gas cap is left off than when the engine is running. Hydrocarbons are part of pollution emitted as gasoline evaporates. Going a step farther, one facet of the emission system is the "Evaporative" portion. This is when the fumes from the gasoline are leaking from the system into the outside air. This is one part of the emission system that can trigger a check engine light. I would say that about 7% of the vehicles that have a check engine light are the result of a loose or inadequate gas cap. But understand that many scenarios are possible with the "check engine light" The vehicle's powertrain computer (note that some vehicles have 17 different computers) will run a series of self-tests. They will only run under certain criteria. And they can be vastly different from manufacturer to manufacturer. Some self-tests are not run until preceding ones have run successfully. So if there is a problem in one particular area that is preventing another self test from running, you can have a situation where one problem is fixed, but another still exists. If you fix a problem and drive the car through a drive cycle that sets the monitor (or self test) the light will go off as it passes that criteria that triggered it in the first place. After 1996, the auto industry went to a idea called OBD II (on board diagnostics). This was to get all the manufacturers onto a similar plane for troubleshooting and powertrain control. While they still differ vastly, many corrections and adaptations were made for technicians to better fix the check engine light problems. Prior to this there were so many different and poor troubleshooting data from a check engine light problem that resolving the problem was much more difficult. Many early warning light of this nature were set to illuminate based on mileage. An Oxygen sensor was one of the things that were meant to be replaced when that mileage was hit. This is much like many current "Change oil lights

Go to your local automobile repair shop and have them hook up a handheld computer, it will read you the code and tell you what the problem is. You can also delete the code and it won't come back up for another couple hundred miles, depending on the car. do it yourself alternative: I have a 1991 Previa. I believe the 92 has the same layout. Turn all accessories off. Engine off. Under the drivers seat is a small plastic box. Pop the lid. With a wire, paperclip, etc, place it in the connector pins TE1 and E1. Turn engine key to "ON", but do not start engine. The check engine light will blink out the code (like telegraph code). I don't have the codes handy, but see for example the Chilton or Haynes manual, or do a web search (good luck).

It should not be a "Check Engine" light, it should be the "Maintenance Required" light. With your key in the OFF position, push in and hold the odometer button. Turn the key to the ON position, the odometer will display 000000 after a couple of seconds. at this time, the maintenance light has been reset. This light comes on approximately every 5000 miles to indicate time for an oil change. If you change the oil yourself, just remember to reset the light even if it is not coming on. This will also work for a 2006 Toyota Corolla.

The odometer will need to be in the odomoter (ODO) mode, not a trip odomoter, for this proceedure to work on newer Toyota's. This did work on a 2008 Tacoma.

It means the ECU has detected a problem with the emissions system. Have the ECU scanned with an OBD2 scan tool. The code it brings up will lead you in the direction of the problem.

replace cat May not be the catalytic converter. This engine code can be triggered by any one of the following:

1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged.

2.) The secondary O2 sensor is malfunctioning.

3.) There is an exhaust leak.

4.) The computer unit is faulty

The Check Engine Light (CEL) is a warning indicator---it means your vehicle's computer has determined that a component or system in your emission control system is not working properly.

When the light comes on, one or more diagnostic trouble codes (DTC) are stored in the engine control module. These DTCs remain even if the light goes out. To address a Check Engine Light problem, the DTCs are retrieved and the appropriate troubleshooting information is followed in order to determine the problem.

so it is not safe to drive with check engine light on. you need to go to repair, those mechanic will use some scan tool for read out the DTCs and earase them. Or you buy one obd2 code scanner to do DIY fault code reader.

Bank 1 catalytic converter efficiency failure.

Bank 1 catalytic converter efficiency failure.

PO303 indicates a misfire on cylinder #3. Normally caused by bad spark plug or plug wire.

Go to this site. It has all codes listed. Mike http://dodgeram.org/tech/gas/Trouble/pcm_fault_code.htm

P0446 Evaporative Emission Control System Vent Control Circuit. The most common cause is the gas cap left off and someone drove the car or the cap was not fully locked it will set the code. Some other causes are leaking evaporative emission plumbing from the fuel tank to the engine compartment, someone changed the fuel pump and did not seal it properly. Failure of a emission component in the evap system. The only way to diagnost these is an OBDII scan tool and a smoke machine the light will come on when the computer does its test of the system and there is a hole as small as .020" 1/20,000 of an inch ! The light can only be turned off by a OBDII scan tool

In general, since you replaced the engine, you most likely disconnected the battery - and that should have reset the codes. If you are getting new codes, something is wrong. Perhaps you have a wiring error or a disconnected sensor. Perhaps one of the sensors is bad.

Most likely it is a dirty or malunctioning oxygen sensor located on the manifold.

There is a small black box under the hood located by the driver side strut tower. The black box (diagnostic box) is only about one inch by 2 inches. If you open the cover to the box you will see a few rows of electrical connectors and on the underside of the "diagnostic box" cover there should be a sticker with a letter and possibly a number that identifys all of those electrical connectors in the box. Take a paper clip and bend it into a "U" shape. Take the paper clip and connect the electrical connector "T1" to "E1" (look at the sticker under the cover). Its possible they may be labeled slightly different, like "Te" or "Te1" or "E". Get a pen and paper and sit in the driver seat of the car. Turn the ignition key to "run" (thats where the dash lights up and the buzzer for ignition and door being open are beeping. DO NOT START ENGINE at this time. You should see the "Service Engine Soon" light start flashing. If not flashing you need to go reconnect the paperclip again. the number of flashes indicates which code it is and what the fault is. For example if you see "flash, flash"....flash, flash, flash" That is code 23. All of the codes will be 2 digits. You should see the same code flash 3 times before the next code is displayed (there may be only one code or lots of them). Then you need to find out what the code means (what the problem is) by either searching online, buying a repair manual for your car and look up the code or call the auto parts store and ask them. You may want to try clearing the codes as described below and if the light doesn't come back on Yipee it's fixed. If you think you have fixed the fault (made the repair) you can reset (clear out the codes) in the computer by removing EFI 15 amp fuse from fuse panel in the engine compartment for 30 seconds. Use the paperclip and jumper the connectors mentioned above, the turn the key to run (NOT START)and if the computer is cleared of all codes the "Service engine soon" light will just do a "flash,flash,flash,flash,flash,flash" with no pause in between. If you get the "flash, flash....flash, flash, flash" then you need to remove EFI 15 amp fuse for a while longer to clear the codes from the computer. Turn off the key and remove the paper clip, Start up the engine and if the light stays out, you have fixed your problem. If the light comes back on you will need to do the paper clip trick again and see what the code is this time. It maybe the same old code(s) or a new code. Good Luck!!

What have you done so far? Have you checked the brake fluid level?

hard to start loss of power rough ideling real bad fuel econemy; it may stall when you stop at stop lights or stop signs etc. or slow down to turn corners

The oil pressure switch is located next to the engine.

no the vehicle can no longer have repair tape on lens. this was just sent out in a memo from pa state inspection board last year

yes