Controlled output
Rapidly removes belt slack during a qualifying crash event.
Safety / SBT
SEAT-BELT PRETENSIONER
Rapidly removes belt slack during a qualifying crash event.
OUTPUT GUIDE90/111
Correct theory and operation
HOW IT
WORKS.
Separate controller command, loaded circuit behavior and useful mechanical or thermal output.
Driver strategy
Identify the installed actuator and driver from vehicle-specific service information. Test only the applicable circuit; different constructions require different connections and equipment.
Current reveals load
Current rise, running level, commutation and turn-off behavior expose winding condition, resistance and mechanical loading.
Feedback closes the loop
Position, pressure, speed, temperature or current feedback may be separate from the actuator circuit and must agree with command.
Common mistakes
AVOID THE
FALSE CLUE.
- Commanding an actuator without proving loaded power and ground.
- Judging command voltage without measuring current.
- Ignoring a binding mechanism, blocked passage or hydraulic fault.
- Bypassing a smart driver or safety interlock.
- Replacing the load without repeating the original test.
Interpreting the recorded data
Normal data pattern
Use the approved scan-tool status, self-test and system procedure. Normal status and plausible feedback support correct operation; no generic oscilloscope pattern is specified for this circuit.
Fault indications
Unexpected fault status, a failed self-test or missing feedback calls for the manufacturer’s diagnostic procedure. Do not probe, resistance-test or energize a restraint or safety circuit merely to obtain a waveform.
COMPLETE TEST SEQUENCE
- Read restraint DTCs and event data without disconnecting components.
- Follow the OEM disable and wait-time procedure.
- Inspect connectors and harnesses using approved handling methods.
- Use only the specified simulator or breakout procedure.
- Restore the system and verify the warning-lamp prove-out.
Know the driver design, current limit, feedback circuit and safety consequences before applying external power.
Diagnostic details
Construction & type-specific testing
Identify the installed design before testing. Construction, signal format and redundant channels are separate attributes; use only the procedure for the actual component.
Seat-Belt Pretensioner
COMPLETE TEST SEQUENCE
- 1. Read restraint DTCs and event data without disconnecting components.
- 2. Follow the OEM disable and wait-time procedure.
- 3. Inspect connectors and harnesses using approved handling methods.
- 4. Use only the specified simulator or breakout procedure.
- 5. Restore the system and verify the warning-lamp prove-out.