I was under the impression that once your “Check Engine” light came on, it stayed on, until a mechanic read the “code” indicating what might be wrong and reset it.
My Check Engine light (2003 VW Golf, 70K miles) has been alternating on and off every couple of days for the past 10 days or so…is it something to worry about? If I bring it in and the light happens to be off at the time, can the mechanic still check the fault code?
The mechanic will be able to see recent codes. My guess though is that your gas cap is not on tightly.
Thanks…I’ve checked the gas cap (and refilled a couple of times during the interim), wondering if maybe it’s not sealing properly?
Yes, some codes are intermittent and others stay on once they are triggered. Both stay in the car’s computer and are able to be read until they are cleared.
Mine came on, I took it to the shop, they said my catalytic converter was probably dead and needed to be replaced, so I said thanks and walked out, and it hasn’t come on since.
It may be from a fluid which is just barely below low level and triggering the sensor. As it heats up, it expands enough so that the sensor goes off. You could check all the fluid levels like brake, steering, transmission, radiator, and washer.
Instead of your mechanic, try bringing your car to an auto part store. Many will download the codes for free. If it is something simple, you can save yourself the mechanic’s charge.
Is that a real problem, or is it like headlight fluid?
It’s not a problem if you live in a state that doesn’t do emissions inspections.
How is your fuel efficiency? I had A simillar thing happen on my Subaru: turned out to be the knock sensor (advances or retards the spark settings depending on how your engine is running). Once it was relaced my mileage got a lot better.
VWs seem to be notorious for random and “phantom” warning lights. I have a 10-year-old Passat which likes to switch on the check engine light and the ABS warning light at erratic intervals. I just ignore it, to be honest. I took it to the garage the first couple of times, and they basically said all they did was reset the error codes.
This is not correct. The check engine light does not know any fluid levels. The CEL illuminates when the ECM detects a problem that would cause an increase in emissions.
Faults are generally of one of a couple types open/short to power or ground to a component, or this reading makes no sense type fault (rpm @ redline, load indicates idle)
CELs can also be triggered by a transmission fault, say for instance the transmission won’t shift into the highest gear due to an electronic fault. The TCM will trigger a fault and request a CEL from the ECM.
Generally the “check engine” light is only used for faults that can cause the car’s emissions to rise above the standard. Temperatures and fluid levels are notified by other warning lights.
I always assumed that, when the “Check Engine” light comes on, you should open the hood and make sure the engine is still there…
In old cars, the Check Engine light meant that there was indeed a serious problem with the engine. But in these new computerized cars, it means practically anything and everything under the sun except the engine.
Umm, you do realize that until cars got computers, there were no check engine lights, right?