How the system works
Follow energy, material, information, and mechanical force through the system before focusing on a single component.
A high-level system map. Component roles and exact circuit behavior vary by vehicle.
- 01InputPower is distributed and protected
- 02Flow 2Inputs report driver and vehicle conditions
- 03Flow 3Modules process information
- 04Flow 4Networks share messages
- 05Protect / verifyOutputs perform the commanded action
Follow the sequence, stop when evidence changes the path, and verify the exact vehicle information before acting.
- 01Power is distributed and protected
- 02Inputs report driver and vehicle conditions
- 03Modules process information
- 04Networks share messages
- 05Outputs perform the commanded action
Major components in context
Protect and route power; a blown fuse is evidence of another condition
System contextReturn current to the source
System contextConvert physical conditions into usable signals
System contextProcess inputs, communicate, and command outputs
System contextCarry power, ground, and communication
System contextSymptom patterns and first direction
Intermittent electrical fault
Record temperature, vibration, moisture, load, and timing before disturbing connections.
Follow the diagnostic path →SYMPTOMNo communication
Check power, ground, network state, and scan-tool coverage before replacing a module.
Follow the diagnostic path →SYMPTOMFuse repeatedly opens
Do not install a larger fuse; isolate the overloaded or shorted path.
Follow the diagnostic path →A system-level diagnostic method
Define what works, what fails, and when
Use the result to support or reject a cause group before moving to a more invasive test.
Obtain the exact wiring and network information
Use the result to support or reject a cause group before moving to a more invasive test.
Check relevant power, ground, and protection points
Use the result to support or reject a cause group before moving to a more invasive test.
Test the signal or circuit under the failing condition
Use the result to support or reject a cause group before moving to a more invasive test.
Confirm configuration and communication before module replacement
Use the result to support or reject a cause group before moving to a more invasive test.
Evidence worth preserving
Full-module scan and communication pattern
Loaded power and ground measurements
Circuit behavior during the fault
Connector, harness, or water-intrusion evidence
Use the VIN, installed equipment, current manufacturer information, and applicable safety rules.
Safety and professional boundary
Circuit and supplemental-restraint caution
Use the correct meter category and test method. Identify airbag, high-voltage, and pyrotechnic circuits before probing or disconnecting anything.