Electrical Diagrams
Passive Seat Belt Diagrams:
Passive Seat Belt Components:
Locations of components
3 Earthing point
In the fascia
20 Ignition switch
On the centre console between the front seats
22A Fuse holder
In the electrical distribution box, in the engine compartment, on the left-hand wheel housing
31 Reversing light switch
Under the centre console, to the left of the selector lever
47S Passive seat-belt warning lamp
In the combined instrument on the fascia
57 3-pole connector
Under the back seat, on the left-hand side
58 12-pole connector
To the left of the steering column, under the fascia, behind the knee shield
59 2-pole connector
One in the engine compartment, at the top hinge of the left-hand door
One in the engine compartment, at the top hinge of the right-hand door
60 Single-pole connector
Two in each door, at the door switch for the passive seat-belt system, behind the trim
Two under the centre console, between the front seats
65 Earthing point
At the back seat
70 Seat-belt switch - driver's side
Between the driver's seat and the co-driver's seat
72 Seat-belt warning lamp
In the centre of the fascia
76 Switch for raising the idling speed (auto.)
Under the centre console, at the selector lever
82 Seat belt/ignition switch warning relay
Under the back seat, on the left-hand side
98 10-pole connector
To the left of the steering column, below the fascia, behind the knee shield
117 Earthing point
Between the ignition switch and the handbrake lever
122 8-pole connector
One under the driver's seat, on the left-hand side, under the carpet
One under the co-driver's seat, on the right-hand side, under the carpet
One under the back seat, on the left-hand side
One under the back seat, on the right-hand side
152A 29-pole white connector
152B 29-pole red connector
In the engine compartment, in the electrical distribution box on the left-hand wheel housing. The connectors are accessible from the interior of the car.
208D Driver's door switch, passive seat-belt system
At the driver's door lock, behind the trim.
208P Co-driver's door switch, passive seat-belt system
At the co-driver's door lock, behind the trim.
306 Logic box for passive seat belts
Under the back seat, on the left-hand side
307D Belt reel for passive seat belts, driver's side
On the inboard side of the driver's seat.
307P Belt reel for passive seat belts, co-driver's side
On the inboard side of the co-driver's seat.
308D Motor with limit switches for passive seat belts, driver's side
Behind the driver's side B pillar, behind the side trim.
308P Motor with limit switches for passive seat belts, co-driver's side
Behind the co-driver's side B pillar, behind the side trim.
309 g sensor for passive seat belts
Under the back seat, on the left-hand side.
310D Fuse (25 A) for passive seat belts, driver's side
310P Fuse (25 A) for passive seat belts, co-driver's side
Under the back seat, on the left-hand side.
311D Motor relay for passive seat belts, driver's side
311P Motor relay for passive seat belts, co-driver's side
Under the back seat, on the left-hand side.
312D Motor relay for passive seat belts, driver's side
312P Motor relay for passive seat belts, co-driver's side
Under the back seat, on the left-hand side
Operation
In certain cars, passive seat belts are provided for the front-seat occupants. The seat belt consists of a motor-driven, two-point diagonal strap and a manually fastened lap strap. The diagonal strap is controlled and monitored by logic box 306.
Regardless of the position of the ignition switch, the seat-belt system is always supplied (+30) across fuses 310 (D = driver's side and P = passenger 5 side). The g sensor 309 is designed to isolate the supply to the logic box in the event of a collision (retardation of more than 0.7 g).
Driver's side
The upper anchor point of the diagonal strap (the carriage on the guide rail) is moved between the A and B pillars by motor 308D, which is controlled by the logic box via relays 31iD and 312D. The travel of the carriage is monitored by the two limit switches 308D:A and B. Limit switch A opens a circuit and thus provides information to the logic box that the carriage has reached the A pillar, and limit switch B opens the circuit when the carriage is locked at the B pillar.
When the door is opened from the outside, the carriage is in the forward position at the A-pillar. After the door has been closed, i.e. door switch 208D is open and ignition switch 20 is in the drive or start position, the coil of relay 311D will be earthed via pin 23 in logic box 306. The relay is energized and one pole of the motor is supplied via the relay contacts, while the other pole is earthed via relay 312D. When the carriage has reached the rear limit of its travel at the B pillar, limit switch B will open. The logic box will then open the earth circuit to the coil of relay 311D and the motor will stop.
When the ignition is switched off or the door is opened, the logic box will energize (via pin 22) relay 312D. The direction of rotation of the motor will then be reversed and the carriage will move towards the A pillar. When the carriage has reached the A pillar, limit switch A will open and the motor will stop.
When reverse gear is engaged,reversing light switch 31 will close and a signal will be applied to the logic box. The driver can then open the door while the ignition is switched on, without the seat-belt carriage moving to the forward position.
The sensor-override solenoid 307D in the belt reel overrides the acceleration and tipping sensors for the diagonal strap. The solenoid is energized while the carriage is travelling between the two limits of its travel, to enable the belt to be withdrawn freely. In addition, the solenoid is energized for 30 seconds after the door has been opened or closed, to enable the seat to be adjusted.
When the solenoid is energized, the circuit will be closed at the upper contacts in the diagram (earth at pin 21) to provide the logic box with information that the solenoid has actually been energized. The lower contacts sense whether or not the strap has been wound up fully on the reel. The contacts are open when the strap is on the reel (not connected to the carriage).
Co-driver's side
The diagonal strap on the co-driver's side is driven in the same way as that on the driver's side. (When relay 311P is energized, motor 308P moves the strap from A pillar to B pillar, and moves it in the opposite direction when 312P is energized.) Reel 307P and door switch 208P have the same function as the corresponding components on the driver's side.
When the co-driver's door is opened from the outside, the seat belt may be at either the A pillar or the B-pillar. If the belt is at the B-pillar, it will move to the A pillar when the door is opened.
When the door is closed and the ignition is switched on or if it is already switched on, the belt will move to the B pillar, regardless of whether or not the seat is occupied.
When the co-driver's door is opened,the carriage will move to the A pillar, and will remain there when the door is closed, unless the ignition is switched on.
Warning system
Warning lamp 475 for the passive seat belts is controlled by the logic box. The lamp will flash:
- when the carriage on the driver's side is moving from A pillar to B pillar
- when the carriage on the co-driver's side moves from the A pillar to the B pillar and if it takes more than 8 seconds to reach the B pillar
- if the carriage is locked at the B pillar and a fault has occurred on the sensor-override function
- if the carriage is not securely locked at the B pillar Lamp 47S will light up with a steady light:
- if the diagonal strap has worked loose from the carriage.
A flashing light has priority over a steady light.
The buzzer in relay 82 is actuated by the logic box (earth at pin 20) and by the driver's side lap strap.
The buzzer will sound:
- while the carriage for the diagonal strap is moving from the A pillar or B pillar when the ignition is switched on
- for up to 8 seconds if the lap strap has not been fastened, i.e. if seat-belt switch 70 is still closed.
Seat-belt warning lamp 72 is not affected by the passive seat-belt system. Lamp 72 will light up for 4 - 8 5 after the ignition has been switched on.
Fault-tracing hints
Check that the supply to the seat-belt system is live. Fuse 310D protects the logic box and the seat belt on the driver's side, whereas fuse 310P protects the seat belt on the co-driver's side. (The seat belt on the driver's side will still operate, even if fuse 310P has blown.) Also check fuses 5, 12 and 13.
As a general rule, always disconnect the connector from the logic box before carrying out fault-tracing on the system. Never take any measurements with the logic box connected or on the pins of the logic box.
The logic box is regarded as an exchange unit, and fault-tracing should start by determining whether the fault is in the logic box or in other components, connectors, etc. Most of the signals to and from the logic box can be checked using the system diagram and the table below. The diagram shows the belt system with the carriages at the A pillars, the car doors open and the lap straps not fastened.
1. Ensure that the ignition is switched off and disconnect the connector from the logic box. Carry out all measurements from the rear of the connector.
2. Turn the ignition key to the drive position and use a voltmeter to check that the following pins in the connector are at battery voltage.
3. Use an ohmmeter to measure between the following pins and earth.
