Current modulation
Sensors communicate by modulating current on the same pair that supplies them, allowing robust wiring in safety systems.
PSI5 / Communication network
PSI5 SAFETY SENSOR NETWORK
Digital airbag and safety sensor communication
NETWORK GUIDE12/14
TOPOLOGYCurrent-modulated two-wire sensor bus
PHYSICALTwo-wire powered interface carrying supply and data
DATA RATETypically 125 or 189 kbit/s
Correct theory and operation
HOW PSI5
COMMUNICATES.
Understand the normal architecture, signaling and message rules before deciding that a voltage or waveform is incorrect.
Synchronization
The controller provides synchronization pulses and validates sensor slots and message integrity.
Common mistakes
AVOID THE
FALSE CLUE.
- Testing with the connector unplugged when the fault only appears under load.
- Using a generic voltage value instead of the vehicle-specific specification.
- Skipping power, ground and reference checks before condemning the component.
- Moving the harness or clearing codes before capturing the original evidence.
- Replacing a part without repeating the test.
Reading the signal
Good waveform / normal communication
The sensor current modulation and synchronization follow the installed PSI5 interface. Data arrives in the allocated timing slots and decodes to plausible measurements with valid status.
Faulty waveform / fault indications
Missing current modulation, invalid timing or repeated data errors may indicate sensor supply, wiring or communication problems. Use the specified current measurement method; an ordinary voltage trace is not a substitute for PSI5 decoding.
COMPLETE TEST SEQUENCE
- Disable the restraint system only as specified.
- Verify connector and harness integrity.
- Capture synchronization and sensor responses.
- Compare slot timing and current modulation.
Confirm the network, topology, awake state and test conditions from vehicle-specific information.