In the workshop guide, 4 and 2 means one of 3 things depending on what the WDS code reads:
B104D - "Crash zone sensor assembly incorrect"
B2226 - "Crash zone sensor system internal circuit disabled" or
B2227 - "Crash zone sensor system communication error"
Looks like the crash zone sensor is located right in the front of the car around where the hood latches. I'd look around the sensor and any wires leading to it for obvious problems. Beyond that I am clueless, good luck.