2002 Chevy Trailblazer

This would explain it, The cam phasing system is a hydraulically actuated phase shifting mechanism. The powertrain control module (PCM) supplies the ignition positive driver and ground circuits. A pulse width modulated (PWM) driver controls the amount that the camshaft actuator solenoid assembly advances or retards the exhaust camshaft. The exhaust camshaft is commanded to a maximum retard position of 25 degrees. When the exhaust camshaft is retarded at the maximum rate, the duty cycle of the signal is at 100 percent. The maximum advance rate has a 0 percent duty cycle. Other than when the camshaft is at full advance, a 50 percent duty cycle is used to maintain a steady retard angle.

"Â This diagnostic trouble code (DTC) sets when the Desired and Actual Cam Phase angle error exceeds its tolerance value for a time period.
Remove the came phaser on the side of the engine block at the cyl head and check for missing screens on the phaser, very common problem. Post back with what you find.