What does it mean?
B2172 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Inertia Switch Input Circuit Open .
Symptoms
- Engine cranks but does not start because the fuel pump is disabled
- No fuel pump prime sound when the key is turned on
- Vehicle cut out suddenly while driving over a bump and would not restart
- Doors do not unlock automatically after the ignition is switched off
- Hazard lights behave abnormally on applications that use the switch for that function
- Fault appears again after driving on rough roads
Likely causes
- Inertia switch tripped by a pothole, a minor impact or a heavy door slam and never reset
- Open circuit in the wiring between the inertia switch and the module
- Corroded connector at the switch, which often sits in a footwell or luggage area where damp collects
- Switch internal contacts worn, burnt or stuck open
- Blown fuse in the circuit that feeds through the switch
- Water damage to the switch after a leaking seal or a wet carpet
- Connector terminal backed out, giving an intermittent open
- Module input circuit failure, only after the switch and wiring are proven
How to fix it
- Confirm the manufacturer definition and the switch location for this vehicle, usually a footwell, kick panel or luggage area
- Press the reset button on top of the switch and then check for fuel pump prime
- Check the fuse that feeds the circuit through the switch
- Measure voltage on both sides of the switch with the key on, a drop across the switch means it is open
- Check continuity from the switch to the module with both connectors off
- Inspect the connector for corrosion, water and backed out terminals
- Repair the harness or replace the inertia switch if it will not pass current when reset
- Clear the code, confirm the pump primes and the engine starts, then road test over rough road to make sure it does not trip again