I had two changed on my 2000 Avalon, and I paid about $350, parts and labor.
Duct Tape
This component is electrically operated by the engine computer. It (on most vehicles) changes the oil pressure in the variable valve timing system to adjust the valve timing. It is very similar to the solenoids in use inside an automatic transmission.
on the engine exhaust cam ..at the front of the cam .
I think you mean the Variable Camshaft Timing Solenoid or VCT Solenoid (F8CZ-6L713-AA) used on 4 cyl engine. It is located under the camshaft cover on the on the exhaust camshaft.
It is an error code that says the variable valve timing is out of limits, may need a timing adjustment or a new vvt solenoid
According to Wikipedia, a variable valve timing is a "process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions".
Variable valve timing.
Variable timing valve train
variable valve timing is where the engine changes valve timing based on the driving situation much like ignition timing is changed to meet the needs of the engine in specific situations. in most cars valve timing is static and determined by the timing gear on the camshaft
Variable Valve Timing with Intelligence
the ford escort zx2 2.0 dohc don't have one it's equipped with vct(variable valve timing) to replace it