What does it mean?
B1608 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Headlamp Switch Input Circuit High .
Symptoms
- Interior lamps never light on unlock or door opening, although the manual dome switch still works
- The courtesy lamp delay function is gone
- The alarm may arm with a door standing open because the same switch signal is used
- No illumination when approaching the vehicle at night
- On the lighting variant, the headlamps cannot be switched on from the stalk or the rotary switch
Likely causes
- Broken wire between the trigger switch and the module, typically inside a door hinge boot
- Latch integrated switch contacts corroded to a permanently open state
- Connector unplugged or a terminal pushed out after door trim or speaker work
- Missing ground return for the switch circuit
- Corroded body side connector in the interior lighting circuit
- Module input open internally
- On applications where this code refers to lighting control, a headlamp switch input reading high from an open circuit or a short to voltage
How to fix it
- Watch the input state in live data while operating the door latch by hand, so door position is not a variable
- Ground the input wire at the module connector: if the lamps then come on, the fault lies upstream in the switch or wiring
- Check continuity through the hinge boot with the door open and closed to catch a wire that only breaks when flexed
- Inspect and clean the connectors, looking for green corrosion and spread terminals
- Test the latch switch for continuity in both positions and replace the latch if it stays open
- Verify the ground return with a voltage drop test rather than a simple beep test
- On the lighting variant, check the switch supply and look for an open between the switch and the module