The reason of U1618 is system wiring, connectors, or other electrical components are also subject to failure. When this code is set, it is imperative that the transmission be checked prior to further vehicle operation.
Carefully observe the resistance level of the sensor (on the screen of the digital volt/ohmmeter) as the temperature is elevated to see if it decreases smoothly
If the resistance level does not decrease with heat and increase as it cools, replace the sensor. If everything has checked out thus far, turn the key to the "ON" position and test for the presence of a voltage (and a ground signal) at the exhaust gas temperature/pressure (or heated oxygen) sensor electrical connector
Some applications are equipped with up to 18 separate control modules. If you choose to tackle this monumental task, begin with a careful visual inspection of all system circuitry, connectors, and fuses
If the fuel shutoff switch and all system circuitry checks out, suspect a defective PCM (or other related controller)
Auxiliary Emission Controls
Vehicle Speed Output Circuit
Kick-Down Switch Failed Short
Broken engine mountings can cause banging and graunching noises. There are two main types of mounting those centrally placed close to the bottom of the block and those higher up the block which mount on to the inner wings or chassis members. U1618 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.
How to turn off U1618 check engine light ?
There are two ways to turn off the check engine light:
A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.