Why does the check engine light go on in a 2000 Pontiac SunFire?

Answer 1

The on board diagnostic computer has detected a problem and has stored a trouble code. Take it to the shop or buy a code reader (Warning, they cost around $200) to find out what is wrong. There's probably 50 different reasons why the check engine light comes on. Normally, the car will run fine but it may get poor fuel mileage or something similar to that depending on what sensor is malfunctioning. I had the same problem and it was only that the gas cap was not tightened when my son put gas in the car last. All I did was tighten the gas cap 5 or 6 clicks and the engine light went out, TRY IT ! It sure saved me a pile of $$$$ At first I thought it was the fuel pressure regulator or EGR sensor (Valve?) If all else fails take it to have the codes read at local dealer, but check the gas cap first to ensure it is tightly on. GOOD LUCK... Mary This is not an uncommon problem with Sunfires or Cavaliers. The engine light is controled by several sensors. These sensors can be set off by just about anything, even just changing the oil. Before you take it anywhere to get the computer read, you may be able to save yourself some money by just unhooking the battery. If it is just a wonky sensor you should be able to unhook the battery and let the memory of the computer reset itself. The best way of doing this is unhooking the battery when you park your car for the night, and leave it unhooked for the entire night. The next morning, hook it back up and go about your business. If the light comes back on again, then you should take your car to a garage to have it checked out. If you haven't heard any noise or noticed any difference in the performance of your car, 9 out of 10 times, it's a wonky sensor. Csn't say I 've come accross a wonky sensor, but anyways: 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