2006 Tuscon Check Engine light just came on, car running fine

It could be an emmissions problem. Sometimes even the gas cap being loose can cause a code. Make sure to tighten the cap when done refuelling...you should hear repetitive clicks when its tight. Other components related to code p0172 are o2 sensor(bank 1) and catalytic converters. Hope this helps!

Sounds like it could have a weak alternator. In gear the idle is always lower than in park. A low voltage situation could cause the gagues to act up

When a 'check engine light' (MIL=Malfunction Indicator Lamp) is turned on, there is a DTC (Diagnostic Trouble Code) set/stored in the ECM/PCM (Engine Control Module/Powertrain Control Module). This code identifies which engine management system component/function experienced a malfunction. Once you pull/read this code, you may begin diagnosis.

weird...first thing to do is get a scanner hooked up to see what caused the check engine light-free, at pretty much any retail auto parts operation-i wouldn't get overly concerned with the gas gauge right now, teh code that tripped the check engine light might explain that problem.

Please see my tip at http://www.fixya.com/cars/r5932051-check_engine_light_check. These are generic instructions. If you get stuck or need specific instructions for your car, please get back to me with model, year and engine info.

{: ) It is still safe to drive as long as you are aware you have enough gas for the trip. The problem is your fuel level sensor could be getting erratic and sending inaccurate signals to the engine control module, thus illuminating the check engine light at times. If you unexpectedly run out of fuel, thats when you will stall on the road. Better have it checked as soon as possible.

a faulty gas cap could cause an engine code to come on with-out and engine problems if you have to do emission tests or smog tests where you live the one thing there to check it that the gas cap is operating properly. but it could also be a sensor when the engine light comes on the car operates in what is called open loop mode the engine runs in preset peramiters set in the ECM it also runs in this mode til the vehicle is at operating temperator so even if the vehicle seems to be running ok the engine light isn't something that sould go unchecked

The purpose of the check engine light is to inform the driver that the car's ECM has registered a problem. It then stores a code in it's memory that can then be "pulled" by a hand held diagnostic trouble code reader and usually the issue an be corrected. More times than not, the car will seem to be running fine even with the light on because the ECM will compensate for the problem as much as it can to keep the system functioning. One thing you can do is remove the gas cap and put it back on making sure that you securely tighten it until you hear 3 clicks. After driving the car for 30-50 miles, the light may go out. If it does then the gas cap was not tightened completely causing air to enter the system (the system utilizes vacuum so it must be sealed air tight). If the light stays on, take it to a Dealer or trusted mechanic for further inspection. ALWAYS BE SURE YOUR GAS CAP IS TIGHTLY SECURED AFTER EVERY FILL UP OR THE LIGHT WILL COME ON AGAIN>

chech gas cap

do not over fill.
check engine light will come on when the vent of the gas tank has gas in it. that is one of the sensor in the newer car since later part of 2005