How do I deactivate the front passenger airbag in my 2001 mitsubishi galant?

You don't have that smart stuff for weight. You can't turn it off. If you don't think they should be in front, because of age or height. Put them in back. I haven't seen a van yet that had this option.

Impact Depending (ID) airbags.
With the Impact Depending (ID) system, you and your passenger are given effective protection proportionate to the severity of the impact.

Conventional airbag systems are unable to differentiate between a severe impact and a lighter one. When they are deployed, they are inflated to the fullest level, making the airbag as hard as possible. In a low-level accident, this is not necessary.
The intelligent ID airbags are equipped with a two-stage gas generator. In a more severe impact, they inflate to their fullest level with minimum time delay, providing maximum protection for the occupants. However, when the accident is less severe, they allow for a slightly longer delay before deployment, protecting the occupants with a more gentle inflation. Whatever the severity of the impact, the airbags ensure that neither the driver nor the front passenger contacts the steering wheel or instrument panel.
A special weight sensor in the passenger seat registers whether the seat is occupied or not. The system can thus differentiate between a passenger and a lighter object such as a briefcase. If the seat is occupied by a weight less than 12 kg, the front passenger airbag is not deployed, saving replacement costs following a crash and potentially leading to lower insurance charges. The front passenger airbag can also be deactivated using a key switch, when a child seat is fitted.
finding a kit to disable the airbag is not going to be easy,noone including dealers will sell or install them on any bimmer,
you could find a kit and buy individual replacement parts,but,i wouldn't recommend it,much less recommend switching the airbag off,personally,I would purchase and install a 5 point restraint that doesn't let the child move forward too much and pull the seat all the way back,the child will not be hurt that way,also in a low speed crash,bimmers dont fully inflate the bag,here is what one owner has to say on a forum about it,
I take my 3, 6 and 9 year olds for drives in my car. These cars are very safe, as is evidenced by my auto insurance premiums being only marginally higher for the Z3 than for my pickup and my wife's SUV. Of course we do have those vehicles for use in transporting the kids most of the time.

Several key things to keep in mind: use a booster seat so the child sits higher, to move the seat all the way back, and to not allow the child to lean against the door--you need to have adequate clearance there.

It's hard for me to believe a side airbag could be worse than hitting the door itself in a side impact--assuming the child is sitting a little away from the door to allow full inflation of the airbag before the child hits it

Disconnect the battery negative terminal.
1. Wait at least 90 seconds after the ignition switch is
turned off and the negative (-) terminal cable is
disconnected from the battery before starting the
operation.
(The SRS is equipped with a back-up power source, so
if work is started within 90 seconds of disconnecting
the negative (-) terminal cable of the battery, the SRS
may be deployed).
2. Do not directly expose the steering pad, front
passenger airbag assembly, center airbag sensor
assembly, front airbag sensor, front seat inner belt
assembly, seat position sensor, occupant
classification ECU, front seat side airbag assembly,
side airbag sensor, curtain shield airbag assembly,
rear airbag sensor or front seat outer belt assembly to
hot air or flames.

you can possibly remove the fuse for the passenger side but keep in mind that if something happens and someone gets hurt while in your car you can be legally held responsible and your insurance may not cover the claims which could amount to 100`s of thousands of dollars.its better to have your child in the rear seat.check with the dealer to see they can legally deactivate the air bag without being sued.they may have to get a special form that will need to be filled out to make it a legal alteration to the safety system.

The A/C evaporator drain tube is most likely blocked. If you have a V6, you're in for a real treat trying to reach the thing to clear it. The tube is on the firewall behind the driver's side rear motor mount, and slightly to the left as you're facing the firewall. It is a 1/2" diameter metal tube projecting about 1/2" from the firewall, and is covered by the firewall sound and heat blocking material which has to be folded back to reach the tube. A pair of what I believe are brake lines are one finger's-width in front of it, making it VERY difficult to get to the tube. (Brilliant design, Mitsubishi!) If you are very dexterous, you can slip a small piece of wire or a cable tie under the brake lines and into the tube from the front to try and clear it. Good Luck!

It is not able to be turned off on your vehicle. you would have to physically disconnect the air bag, then none would work. Children that young should not ride in the front seat anyway.

is there fluid in box check as if fluid is low u will not get gears

deactivation on airbags can only be done at the dealer on request where a key system will be in stall for you to deactivate when ever

The airbag system in this car is second generation smart airbags, there is no switch, if the weight in the passenger seat is not at least 50 pounds (there is a sensor in the seat cushion) the airbag is switched off to the paassenger seat, but small children should always be in a approved child seat in the back seat anyway.

Children in car seats should never be put in the front seat.  In fact children under the age of 13 should never be in the front seat.  Their bodies are not large enough or strong enough to sustain the impact of a crash or an airbag.  For your baby's safety and your peace of mind it'd be best for you to keep your baby in the rear seat and get a mirror for the back seat to see what's going on.