Normal Operation

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

The belt tension sensor operates in conjunction with the Occupant Classification Sensor (OCS) system. The Occupant Classification System Module (OCSM) 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 OCSM) 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 OCSM) must be installed as an assembly. Refer to Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) .

The OCSM 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 warning indicator. The secondary air bag warning chime will also be activated.

Fault PIDs^a	Description	Fault Trigger Condition
2909_29_OD and 2909_29_CM	Front Passenger Side Belt Tension Sensor Short to Ground	When the Occupant Classification System Module (OCSM) senses a short to ground on the belt tension sensor circuits, a fault will be indicated.
2909_31_OD and 2909_31_CM	Front Passenger Side Belt Tension Sensor Circuit Fault	When the OCSM module senses a failure on the belt tension sensor circuits, a fault will be indicated.

^a Fault PIDs that end in OD indicate an on-demand status and are associated with on-demand DTC B2909. Fault PIDs that end in CM indicate continuous monitor status and are associated with continuous DTC B2909.

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
Belt tension sensor
OCSM