900 L4-1985cc 2.0L SOHC (1988)
solenoid acts on the belt reel and the microswitch signals the ECU as to the solenoid position. These are key signals and both must be checked. See the
Service Manual 3:2 or the Saab Passive Restraint System Training Manual for checking the reel. The seat belt reel may be checked with a digital
volt-ohmmeter (VOM) at the back of the plug for the ECU (Figure 4). Some expanded testing advice is given here.
When testing the reel with the ECU unplugged, pin 21 (driver's side) should become grounded when pins 25 and 8 are jumped. Pin 17 (passenger's side)
should become grounded, when pins 25 and 4 are jumped. When a ground occurs this indicates that the solenoid and the microswitch in the seat belt
reels are working properly. If ground signals are not received, inspect electrical
connections. If a problem is traced to a seat belt reel, the reel must be replaced. A reel cannot be repaired.
Transport Mechanism - The mechanism is driven by a motor that moves the upper part of the shoulder belt between the "A" pillar and the "B" pillar.
Limit switches at each position signal the ECU when the shoulder belt is at the "A" or "B" pillar. Switch failure can cause the transport motor to run
continuously, even if the ignition is off.
FIGURE 5 - ALWAYS TEST WIRE CIRCUITS FROM THE BACK OF THE ECU PLUG.
Always check the "A" and "B" pillar limit switches as part of your diagnostic routine. Test the switches with a digital VOM at the back of the plug
(disconnected) for the ECU (Figure 5). Both "A" pillar switches should be open with the driver's and passenger's belt at the "A" pillar. The switches must
be closed when the belts are at the "B" pillars. The same is true for the "B" pillar limit switches. They should be open with the transport mechanism at
the "B" pillar and closed at the "A" pillar. The limit switches are located in the motor assembly. They are not repairable. In the case of a defect the motor
assembly must be replaced.
