I have 2000 audi a4 i replaced 2 air bags & seat belt tensioners i need to retriger air bag controll unit HOW

B2909 Belt Tension Sensor Fault RCM REFER to Section 501-20B .
Normal Operation The belt tension sensor operates in conjunction with the occupant classification sensor (OCS) system. The electronic control module (ECU) for the OCS system interprets a variable voltage signal provided by the safety belt tension sensor to identify the possible presence of a child safety seat in the front passenger seat.
The OCS system components (seat cushion foam pad, bladder with pressure sensor and electronic control unit) are calibrated to each other and are serviced as an assembly. The OCS system components are not to be installed separately with the exception of the belt tension sensor. If a new OCS system, OCS system component or seat cushion foam pad are needed, a new OCS system service kit (seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly. Refer to Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) in this section.
The ECU monitors the belt tension sensor circuits for faults. If a fault is detected on any of the belt tension sensor circuits, it will report the failure to the restraints control module (RCM). The RCM will store DTC B2909 in memory and, depending on the fault, flash a LFC on the air bag indicator. The secondary air bag warning chime will also be activated.
Possible Causes A belt tension sensor circuit fault can be caused by:

• wiring, terminals or connectors.
• an open circuit.
• a circuit short to voltage.
• a circuit short to ground.
• a faulted belt tension sensor.
• a faulted OCS ECU.

control module needs to be replaced typical problem with the audi's 1999-2004

Hi there

Not normal at all. Could be a connection problem at the air bag pre tensioners, the part where your seat belt clips in to when you wearing the seat belt, or could be the hooter ring contact that is not good or the airbag/s has been activated then airbag computer and seatbelt stalks that activated has to be replaced.

Hope this sheds some light.

Regards
Phillip

is it the pass side air bag you will also need the seat air bag to be turn'd off to. you need to take to a garage. and say its needed to be turn'd off there will be a small charge. ( baby car seat is needed fitting) you can buy a air bag software kit to disconnect the air bags on that seat area. op-com or other makes just check it has the softwear to disable air bags.

not normally the controll unit yes and the poped air bags but the rest will be ok the controll unit stores any accidents and will have to be replaced it cannot be reset

Yes!!! You can replace it yourself.(Dont let others fool you into paying extra or telling you otherwise.)
-This is for pontiac grand ams 1999-2005 only.
-There are no frontal airbag impact sensors nor are there belt tensioners.
-The SRS system consists of only the (driver airbag) ,(passanger airbag),and the (airbag control module) in 1999-2005 grand ams.

If you crash/wrecked and airbags deployed you will need.
-Driver and Passanger airbags
-Airbag control module

You can buy cheap airbags from a local junkyard any year from 1999-2005 will fit.
You can also find an airbag control module for cheap at your local junk yard BUT YOU MUST FIND ONE WITH THE SAME (PART NO.) AND (SERV NO.) AS THE ONE YOUR REPLACING.The (part no.) and (serv no.) should be at top left of airbag control module.However it does (Not) have to match numbers under barcode or the numbers at the far bottom right of airbag control module.

After you get both airbags and airbag module
-Disconnect car Battery
-Replace airbags
-Replace airbag module (under passanger seat)
-Double check all connections and connect battery.

Congradulations!Your airbags should be back online.

Notes: Two torx 35 head screws hold the driver airbag, access is through two holes behind steering column.
To remove passanger airbag you have to remove glovebox it uses (7mm)screws.After you remove you will see a pair of (10mm)screws holding airbag.
To remove airbag control module First remove passanger seat 2(15mm).Then after removing you will notice a raises area kinda like a vertical bump.Take a razor blade to your carpet and cut it to explose the module underneath.
The airbag module is held by three screws depending on the year of your car it varies.Most likely 3 (10mm).

front or back if front there will be at least 4 bolts holding it to floor push the seat all the way back there will be a couple of plastic covers at the end of the runners remove these and there should be a couple of bolts or starbolts remove these then push the seat till its all the way forward and do the same with the rear ones if the seat belt it atatched to seat remove that as well seat should come straight out but check underneath as some times there are wires connected to the botom of the seat air bags heated seats ect remember if it has air bags in the seats to disconect the battery and let it power down for a few minuets as if any air bag is disconected it will come up on the dash as a fault and will need reseting hope this helps ivan

The airbag module is a serious safety device and should not be tampered with. The entire air bag system ie module , air bags, seat belt tensioners etc are treated as one unit and there fore not a serviceable item or part replacement there of. The module should be located in the bowels of the dashboard (yellow wiring ) and mounter to the bulkhead. Do NOT tamper or adjust any componants.Good luck

the likely fault is the cables running to the seatbelt pre-tensioners under the drivers or passengers seat in the front of the car.

This may be simply the plug and socket have become seperated from sliding the seat back to clean, a common fault, or the airbag "clockspring" connection unit in the steering wheel has a broken ribbon cable inside the column housing.

To see if its the airbag clockspring, buy a 4 ohm resistor from maplin or radio shack, disconnect the battery on the car, unplug the airbag in the steering wheel and connect the resistor across the 2 contacts in place of the airbag, reconnect the battery, if the light goes out the clockspring is the fault, if not its the SRS system wiring under the seats.

It is fairly complicated to remove the instrument panel to replace the light bulb. It requires you to remove the steering wheel and airbag module and several other components.

The sound you hear may be the coolant pump for the turbo.