Airbag sensor testing

Bought a tacoma from an auction, dented bumper, but no hood, or fender damage. The plastic grill took some of the hit , rad support was pushed back, but nothing hitting the fan. Beat the rad support out a bit, changed the bumper, it now looks clean, except the airbag light blinks... seat belts work fine, Airbag didn't deploy, so I think I'm good,
I want to send my Airbag off to get reset ($50). My question is how do I test the impact sensor to keep from generating a fault code to the srs mod?. My obd reader doesnt see any srs codes only the dreaded p0420 (420 lol). I'm thinking the sensor is open in it's natural state, then completes the circuit when a bump happens, telling the computer someone's head is about to hit the dash... so with a low impact and nothing else deployed, would the sensor stay closed? I'm guessing no, but I've been wrong before. Anybody been here, done that?
After all there are no new problems, just first time experiences. Thanks

 

Airbag module to get reset

 

Continuing, disco'd the battery, removed it for better access, then waited to de-energize the srs circuit, pulled both front impact sensors, checked for resistance, got the same reading from both, not open, not shorted. There's a youtube video of someone taking an exact duplate sensor appart, a swinging cam closes the circuit (upon impact), so if it shows no resistance. If it's open before the resistor then it would show that. The path is made to travel through the resistor so it's "seen" by the srs. Feel confident these won't trip my reset module...

 

SRS codes are hard codes that can’t be read through the OBDII port. My 99 currently has an SRS trouble code, my tech had to hook his gauge up to a diag port in the engine bay, and had to supply the port with 12volts for it to work. That was the only way he could read the SRS system. My trouble code is for the passenger seatbelt pretensioner and it wasn’t lit until after I got into a crash. There’s a lot involved in the SRS system, I would take it to the dealer or a body shop before messing with the SRS system. If you don’t know what you’re doing, you can cause it not to work, or set off your airbag.