Malfunction Indicator Lamp

when you turn on your ignition to the point before engaging the starter all your warning lights should light up. The Engine Check Light is very obvious, except they throw convention to the wind and show it as 'Service Engine Soon' lamp 'Malfunction indicator lamp (MIL)'.
Page 63 - Section 2-7 Instruments and controls

Malfunction indicator lamp (MIL) If this indicator lamp comes on steady or blinks while the engine is running, it may indicate a potential emission control malfunction. The malfunction indicator lamp may also come on steady if the fuel filler cap is loose or missing, or if the vehicle runs out of fuel. Check to make sure the fuel filler cap is installed and closed tightly, and that the vehicle has at least three gallons of fuel in the fuel tank. After a few driving trips, the lamp should turn off if no other potential emission control system malfunction exists.

http://www.vadennissanservicecontracts.com/owners-manual/nissan/2001-Nissan-Frontier.pdf

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• Check Malfunction Indicator Lamp (MIL)
• Check Wiring/Connectors from/to Malfunction Indicator Lamp (MIL)
• Check Control Module Coding
• Check/replace ignition/starter switch
• Check relay on left plenum chamber for execive wear

EOBD II Error Code: P0117
Fault Location:
Engine Coolant Temperature (ECT) Sensor (G62) - Low Input
Possible Cause:
Malfunction Indicator Lamp (MIL) Triggered on first occurrence.
Coolant thermostat.
Wiring short to earth.
Engine coolant temperature (ECT) sensor.

EOBD II Error Code: P0340
Fault Location:
Camshaft Position (CMP) Sensor A (G40), Bank 1 - Circuit Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) active.
Wiring from/to Camshaft Position Sensor (CMP) faulty.
Camshaft position (CMP) sensor faulty.
Timing misaligned.
Possible Solutions:
Check Wiring from/to Camshaft Position Sensor.
Check Camshaft Position Sensor.
Check Timing.

EOBD II Error Code: P0500
Fault Location:
Vehicle Speed Sensor (VSS) - Circuit Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) Non Emission Fault - No warning light.
Wiring.
Vehicle speed sensor (VSS).
Engine control module (ECM).

Go to an Autozone, Oreilly, or Advance autoparts store and get a free scan. Get the code number and proceed from there. They have parts and sometimes CD's with Help topics.

The light could mean many possible issues. You will need to get someone to read the code to determine what is the potential problem. You have numerous sensors that can set the light off,

malfunction indicator lamp or MIL, means that something is out of specifications from what is expected by the computer.

Have the car scanned with an OBD-II compliant scanner that covers 1996 and up vehicles.

You can buy your own at Walmart or Sears for under $100.

usually a sensor has gone bad. have it check by a mechanic on the computer.

P0650 Malfunction Indicator Lamp (MIL) Control Circuit Malfunction

Malfunction Indicator Lamp (MIL) is located on the instrument panel. When the ignition switch is turned ON without engine running, MIL will light up. This is a bulb check. When the engine is started, MIL should go off. If MIL remains on, the on board diagnostic system has detected an engine system malfunction.

Possible Causes:

Harness or connectors (MIL circuit is open or shorted.)

MIL bulb may be faulty

Malfunction indicator light is the same as Check engine or Service engine soon. It only tells you that your vehicle needs a checkup but does not mean there is a big problem.

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The Malfunction Indicator Lamp or MIL (Also called the check engine light or service engine soon light) comes on when the on board computer detects an issue with the operation of the engine or transmission.

The best thing to do is to take the vehicle to an auto parts store like Autozone and have them hook up their scan tool to the vehicle and read the code. They can read it, tell you what it is and also tell you what the code means.

If it is pointing to a faulty component or sensor and you replace or repair the component the the light will go off on its own after the computer sees that the malfunction is no longer present.

You can have the code cleared, but if whatever caused the light to come on in the first place is not addressed then it will just come back on eventually.