Mechanics

ENGINE LIGHT DOESN'T GO OFF

Toyota Other

Hi,
I have 97 toyota camery LE with 109000 miles on it. Recently the check engine light came on and the mechanic checked the code to be P0125 and replaced the thermostat as the engine was not heating properly. They showed me the temp too which was around 120 degrees. They replaced the thermostat but after a few hours of driving the light came on again.
Then they changed the temparature sensor but the light is still came on. Now they say the computer's software may need to be refreshed.
any ideas how to rectify it?
Thanks
Avatar
Pra123
February 15, 2007.




Need to know the codes present.

Here is some background: SES light
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 It is a warning light that is illuminated when there is a problem affecting the EMISSIONS of the vehicle. Don't let it bother you as it is a good thing once you understand it. One point that was brought up 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 a small percentage 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 multiple computers aside from the powertain computer) will run a series of self-tests. They will only run under certain criteria. And they are different from manufacturer to manufacturer. Some self-tests or monitors 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.
There are many different sources for the light to come on. Anything that caused combustion to fail, commonly called a misfire will set the light. Various sensors such as oxygen sensors that evaluate the exhaust before and after the gases are burned in the converter. Transmission codes may set the check engine light to appear. If the car is running okay, get it fixed in a reasonable amount of time such as within the month. It will probably save you fuel if you do. However if the Check engine light is flashing, you should not be driving it as damage is being done to the converter. Some emission components are covered beyond the standard warranty. The converter for example is covered up to 80,000 miles by the manufacturer.
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, 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 that are set based on a pre-set mileage.
To start testing for the check engine light, you ll need to find 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. There are self-tests for the oxygen sensor circuit, egr system, evaporative system to name a few. Therefore, another problem may exist. It is emission related.

OR hook up a scanner that is capable of clearing codes, and hope that it won t come back on. But don t bet on it. Lastly, disconnecting the battery in some cars will clear the memory of the computer and may temporarily turn the light off. Beware that this may also cause other problems such as the car not rembering it s idle and will have to relearn it, the radio may be rendered inoperative or in the case of the new Toyotas, the air bag can blow.-Bclear!
AD

Paul

I thought you're an auto tech, I am very impress of you being a novelist. Outstanding my man, Keep on Techk. It carries the name as writer. I thought I was an old dog-but am learning new tricks from here' I love this site. Get to express my ancient knowledge.

BTW did you get my VD msg thru PM

Here's more reading material to learn about that Idiot lite-that gets people panicky
. Check Engine Light On?
Is your " Check Engine Light" on? An illuminated " Malfunction Indicator Lamp" (or MIL ) means a fault has been detected in the engine control system and one or more " diagnostic trouble codes" (DTCs) are stored in the engine's computer. Depending on the nature of the fault, the lamp may come on and go off, remain on continuously or flash. Some types of intermittent faults will make the lamp come on only while the fault is occurring. When the fault goes away, the lamp goes off. Other types of problems will turn the light on, and it will remain on until the fault is diagnosed and repaired.

The Check Engine lamp has proven to be a great annoyance to many motorists (as well as professional technicians) because it seems to have a mind of its own. For one thing, it doesn't tell you anything about the nature of the problem or what the trouble code might be. It could be something serious - or it might not. There is no way to know without performing a diagnostic test on the system. Consequently, you don't know if you should stop immediately or ignore the light and keep driving. If no other warning lights are on, and the engine seems to be running normally (no unusual noises, smells, vibrations, etc.), It is probably safe to assume the problem is minor and won't hinder your ability to continue driving. But sooner or later, you should have the cause of the light investigated.

Whenever the Check Engine light comes on, a " diagnostic trouble code" (DTC) or fault code is recorded in the powertrain control module (PCM) memory. The trouble code has a number that corresponds to the type of fault. Some problems can generate more than one trouble code, and some vehicles may suffer from multiple problems that also set multiple trouble codes.

SETTING TROUBLE CODES
In most older vehicles (those made before 1996), disconnecting the computer power source or disconnecting a battery cable could erase fault codes -- at least temporarily until the trouble code resets and turns the check engine light back on. But on many newer vehicles, you do NOT want to disconnect the battery because doing so can wipe out the computer's memory settings as well as the trouble codes. This may affect the operation of the transmission, climate control system and other functions.

In most newer computer systems, fault codes are stored in a " nonvolatile" memory that is not lost if the battery is disconnected. The trouble codes remain intact until they are cleared using a scan tool.

When you need more just ask and you shall receive

Good Luck!

Tiny
Rasmataz
Feb 16, 2007.
Hey Jess,

Actually I'm barley a Tech, really a Service Writer. I get my hands a little dirty, but try to avoid it as best as possible.

I do enjoy writing and had an article published in MotorAge magazine 2 years ago. I too enjoy learning here, one of the reasons I stick around. There is a great collection of folks here that are pretty intense and passionate about this.

My rule of thumb on the CEL is get it checked out within a month if the light comes on and is not flashing or having a drivablity problem.


AD