The automobile dictionary meaning of the U1021 Code is U means Network Code Problem is climate control system, lighting, airbags, etc. 1 for MFG – Manufacturer Specific. 0 for Fuel And Air Metering. 2 for Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and 1 for TFP Valve Position Switch-Drive Without Drive Ratio. The engine code U1021 OBD2 refers to the camshaft timing. In this case, if the cam timing is high backward, the engine light will be illumined and the code will be set. Gasoline engines’ usage spark plugs to reason an blast of fuel in the cylinder. You need to use expensive machines for solving the car engine.