U0644 Smart Auto Trouble Code

U0644 Smart OBD2 specifically refers to the camshaft (cam) timing. In this case, if the cam timing is over-retarded, the engine light will be illluminated and the code will be set.

When you fill your car with gas, the vapors in the tank get forced into a canister filled with activated charcoal. Also, on a hot day as the gas heats up and vaporizes, those same vapors push into the canister where they're stored. But the charcoal can only hold so much vapor. At some point it has to be emptied. The emptying process is called canister purge.

U0644 Smart Possible Solution:

Disconnected, dirty or fouled spark plugs are common causes for engines that won't start. Spark plugs typically need to be replaced every season or 25 hours of use. You should also check that the spark plug gap is set properly. If your spark plugs look good, problems with your ignition system can also preventing a spark. These can range from a faulty spark plug lead, shorted kill switch or flywheel key damage.

U0644 Smart Description For All Models :

U0644 Smart Trouble Repair :

The sensors receive a 5 volt reference signal from the PCM. As pressure readings change, the sensor varies the voltage and the computer reads that to determine input. In the case of a broken wire, the sensor never sees the voltage and the computer assumes a major fault. So if you get this U0644 Smart code, first check to make sure you're getting a good 5 volt reference signal at the sensor.

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