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Hi.

The air bag or bags was/wer deployed? Both?

The driver side air bag replacement part will run you about 700 dollars from a dealer parts department

However...

Toyota recommends, whenever an air-bag is deployed, to replace all of the sensors.

The front sensors are about 90-100 dollars each, and the center air bag sensor (the main electronic control) is about 350 dollars.

Also, the spiral cable assembly (the 'clock-spring') is an additional 250 dollars

Some states require the supplemental restraint system (the air bags) to be functional for inspection, some do not

Correct. Very expensive to repair

THat is why we find these cars in the salvage yards with light damage; the air bag replacement costs tip the scales to the side of "totalling" the car

A dealer can hook up their scan tool to the car, and read the failure codes. It could be something as simple as replacing the clockspring. Without the codes, all I would be doing would be speculating

The code(s) will indicate what is needed to rectify the situation

Most dealers will scan the vehicle for a reasonable cost.

If you press on the horn pad, on the wheel, there should be a significant resistance.

...as in something there, under the vinyl.

I have observed cars come in with an intact horn pad, and noi bag installed. Apparently, there are people manufacturing pads to hide the fact that the bag is missing. Nefarious, but it is happening.

Yes. Do not purchase the car until you know exactly what the replacement costs are going to be. Add in a passenger side airbag, you can spend up to 2800 dollars parts and labour