Answering my own question, courtey of a Racer X post from 2006 (Thank You Hamal):
DIAGNOSTIC TROUBLE CODE 45
Center Radiator Primary Crash Sensor Not Mounted to Vehicle Properly
Normal Operation
The air bag diagnostic monitor measures the resistance between Pin 21 (Circuit 620, P/LB) and Pin 3 (Circuit 57, BK, diagnostic monitor reference ground). If the air bag diagnostic monitor measures a difference of more than 2.0 ohms between Pin 21 and Pin 3, it will flash out code 45.
Note that Circuit 620 (P/LB) is grounded to the side of the center radiator primary crash sensor case and the case is grounded to the vehicle at its mounting point.
Possible Causes
High resistance on Pin 21 (Circuit 620 P/LB) to ground can be caused by:
12. A poor connection due to loose mounting or dirt at the center radiator primary crash front air bag sensor and bracket mounting location.
13. An open or damaged wire (Circuit 620, P/LB) from Pin 21 of the air bag diagnostic monitor harness connector to center radiator primary crash sensor.
14. An open circuit inside center radiator primary crash sensor.
Pinpoint Tests--Diagnostic Trouble Code 45
² 45-1: CHECK FOR DIAGNOSTIC TROUBLE CODE
² 45-2: DEACTIVATE SYSTEM
² 45-3: CHECK CENTER RADIATOR PRIMARY CRASH SENSOR GROUND
² 45-4: MEASURE RESISTANCE OF CENTER RADIATOR PRIMARY CRASH SENSOR TO GROUND
45-3
DIAGNOSTIC TROUBLE CODE 45
45-3 CHECK CENTER RADIATOR PRIMARY CRASH SENSOR GROUND
l Disconnect center radiator primary crash sensor from harness.
l Measure resistance between P/LB wire in center radiator primary crash sensor connector and a nearby, good chassis ground. Make sure that this ground is clean and bare.
l Is resistance less than two ohms?
Yes
INSPECT circuit between Pin 21 of air bag diagnostic monitor and center radiator primary crash sensor. CHECK all interconnects and splices for poor connections. Make sure to CHECK in-line connector for proper crimps, etc. SERVICE any poor connections. RECONNECT system. VERIFY system. REACTIVATE system.
No
REMOVE screws retaining center radiator primary crash rear air bag sensor and bracket. CLEAN mounting surface of center radiator primary crash sensor and chassis. INSTALL center radiator primary crash rear air bag sensor and bracket. TIGHTEN screws to proper specification. GO to «45-4».
45-4
45-4 MEASURE RESISTANCE OF CENTER RADIATOR PRIMARY CRASH SENSOR TO GROUND
l Measure resistance between P/LB wire in center radiator primary crash sensor connector and a good chassis ground.
l Is resistance less than two ohms?
Yes
RECONNECT system. VERIFY system. REACTIVATE system.
No
REPLACE center radiator primary crash front air bag sensor and bracket. RECONNECT system. VERIFY system. REACTIVATE system.
