The passenger airbag sensor is not sensing lighter passengers, the airbag stays on when we need it off.

I experienced the same type of issue with my Corolla and I took it in and turned out it was a connection that had come loose. Also, check to see if there are any recalls for your airbags or sensors. That was another issue that mine had.

Hello Collette,

(Owner Manual Page 2-68)
The passenger sensing system turns off the right front
passenger frontal airbag and seat-mounted side
impact airbag under certain conditions. The driver
airbags and the roof-rail airbags are not affected by the
passenger sensing system.
The passenger sensing system works with sensors that
are part of the right front passenger seat. The sensors
are designed to detect the presence of a properly-seated
occupant and determine if the right front passenger
frontal airbag and seat-mounted side impact airbag
should be enabled (may inflate) or not.

I'm not sure if a purse or other light weight objects would activate the passenger airbag but if your display is showing random passenger activation it would be best to have a qualified dealer check into it...better safe than sorry.
http://www.gm.ca/media/owners/manuals/2010_Chevrolet_Malibu_Manual_en_CA.pdf

As far as the passenger airbag is concerned - OFF may be normal. This is an excerpt from the owner's manual (page 1-67).

Passenger Sensing System
The vehicle has a passenger sensing system for the
right front passenger position. The passenger airbag
status indicator will be visible when you start the vehicle.
The word OFF or off symbol will be visible near the
clock, located in the center of the instrument panel,
during the system check. See
Passenger Airbag Status
Indicator on page 3-27
.
When the system check is complete, either the words
ON and OFF or the symbol for on and off will be visible
under certain conditions.
The passenger sensing system will turn off the right
front passenger frontal airbag and seat-mounted
side impact airbag (if equipped) under certain conditions.
The driver airbags are not part of the passenger
sensing system.
The passenger sensing system works with a sensor that
is part of the right front passenger seat. The sensor is
designed to detect the presence of a properly-seated
occupant and determine if the right front passenger
frontal airbag and seat-mounted side impact airbag
(if equipped) should be enabled (may inflate) or not.


The horn is another matter. There are four possibilities here. I will list them in order of likelihood:

1. Bad switch in the steering wheel. These are common failure items.
2. Bad horn relay
3. Bad horn assembly itself
4. Faulty wiring in the horn circuit (including fuse)

You can have the switch(es) replaced in the steering wheel, but they are just as likely to fail again. I have had this issue happen in the past, and I simply went to the bottom of the steering column, found the horn button wire, and installed a dashboard mounted horn button. It is legal in most jurisdictions for inspection purposes as long as the button is easily accessible by the driver.

Could be a problem with the sensor in the seat. The system thinks someone is sitting in the seat and the seat belt is not fastened.

sounds like the sensor in the seat may have stuck on or the control module threw a code because it was sensing weight in the seat but the seat buckle was not latched...try clearing the code and see if it comes back..if it does check for seat sensor for proper function

Its a weight sensitive sensor, so you would probably have to come up with some sort of resistor. I doubt you can bypass it.

there is no switch for the passenger airbag. it is activated by a weight sensor in the passenger seat. if it senses over 50 pounds in the passenger seat it will then turn the passenger airbag on

umm not sure on the 02 but sounds like u are looking at the passengers side air bag light when that lights on means there is a problem with it and its not working so if its off that would be the problem and the reason it turns on some of thiem have a x2 symbol on thiem to let u know its the passenger side

Most likely a problem with the passenger seat sensor, BUT you always start by getting the trouble code from the computer. Otherwise you're just guessing.