C0603 indicates the active air dam (or active grille shutter) control circuit is reporting a voltage higher than the calibrated range. The module that commands the air dam actuator detects an open circuit, short to power, or internal driver fault on the high-side drive. The air dam will typically be disabled and default to a fixed position until the fault is corrected.
The actuator assembly contains a DC motor and integrated position sensor; an internal open winding or sensor fault can pull the feedback circuit high.
Damaged, corroded, or disconnected wiring between the control module and actuator can cause the driver to see a high voltage on the control or feedback line.
Water intrusion or fretting at the actuator or module connector creates high resistance or an open, which the module interprets as a circuit-high condition.
The high-side driver inside the body control module or dedicated aero module may have failed open, though this is less common than actuator or wiring faults.
Ice, debris, or physical damage preventing actuator movement can cause the position sensor to report an out-of-range high voltage.
Yes, the vehicle is drivable. The air dam will default to a safe position (usually open), which may slightly reduce fuel economy and increase drag but does not affect engine or transmission operation.
No. The fault is almost always in the actuator, its wiring, or connectors. Control module failure is rare and should only be considered after the actuator and circuits are verified good.
Clearing the code only turns off the light temporarily. The code will return on the next ignition cycle or when the module retests the circuit unless the underlying fault is repaired.
In most jurisdictions the active air dam is not a monitored emissions component, so C0603 alone will not cause an OBD-II readiness failure, but the illuminated MIL may result in a visual inspection failure.