125,000 milage and service engine soon light came on, what's wrong

all part stores will scan the car for free and I need the codes please

Always on,why is that?

Those thype of lights have been on all vehicles
for over 30 years as required by the govt in north
america at least,so how is it your not checking for codes
almost the same day you get a light on your dash

That is a MIL Lamp or Check Lamp indicating your car
has a possible faiure in one of it's many systems

You check for codes right away & diagnose,resolve or
repair within a week inless it isn't something that would
ruin your engine or trans etc.

The wording service soon is misleeding & nothing to
do with you getting some type of service at your convenience,
it is a serious problem untill you check for codes & at least
have some indication of the system effected

Scan the computer for trouble codes. Use an OBD 1 scanner or code reader. The light having come on means there is a stored code or codes to direct you or a technician to the problem sensor or circuit.

I assume you resolved the issues by now

Check lights have been on all vehicles for 31 years,
so you shouldn't be asking about them

Does not matter what light comes on your dash

The procedure is always the same
Check for codes
Diagnose & repair code related issues first

It means your vehicle's onboard computer system has self-diagnosed some kind of problem.
use maxiscan us703 clear the fault codes.

If the "check engine" light illuminates, it will either blink or remain constant, depending on the problem. Either way, you should have the vehicle checked by a mechanic, although a blinking light or, on some cars, a red light instead of a yellow/orange light indicates a problem that needs immediate attention. In late-model cars, a blinking light usually indicates an engine misfire so severe that unburned fuel is being dumped into the exhaust system, where it can quickly damage the catalytic converter, requiring an expensive repair. If that happens, you should reduce power and have the car or truck looked at as soon as possible. If the light is steady, the problem is not an emergency, but you should schedule an appointment as soon as possible.

Today's automotive computers often try to compensate when there's a problem; so you may not notice deterioration in performance, even though your fuel mileage is suffering and your vehicle is emitting unacceptable levels of hydrocarbons and other pollutants. This and other additional details can find it in Check Engine and OBD Fault Codes articles.

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Common cause is BAD GAS..

This happens when your odometer reaches a set milage,indicating mantainance.Just what needs service I don't know.If you do nothing your check engine light will stay on soon.Many Pep Boys, Auto Zone will read your onboard diagnostic for nothing ( a small Tip is expected ).Then you'll know what it is.Don't rush into repair.Get estimates.It could be very minor..Filters or mid... EGR Valve ,Cat Converter.Good Luck

yes...they do program the computers to come on or give a "service engine soon" light so that you will bring them back into the dealership....if you have access to an obd2 diag tool you can reset the codes yourself

knock sensor is located on the block usually under the intake. nissan has problems with these sensors. i have chaunged plenty of these on nissans in the past year. this has no affect on your gas mileage. this sensor picks up misfires on the engine. sometimes you might have rough idle and can't feel it in the drivers seat but the knock sensor can. i would suggest maybe a tune up spark plugs, air filter, fuel filter first before going to take apart a bunch of things to change a sensor. the sensor is designed to pick up any differences in motor quality and will throw the engine light on. sometimes the problem is the knock sensor, or there is an underlying cause that the knock sensor is reading.