What does it mean?
B1640 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Front Right Turn Lamp Control Circuit High .
Symptoms
- Front right indicator does not flash, or lights very weakly
- Indicator flashes noticeably faster than normal, which is the classic sign of a missing lamp
- Bulb out warning and a changed audible reminder when the indicator is used
- Hazard warning flashers behave the same way on that corner
- Trailer indicator function, where fitted, works incorrectly on the right side
Likely causes
- Front right turn signal bulb burned out or removed
- Corroded bulb socket, a very common problem at the front corners where water and road salt collect
- Broken wire or a pushed out terminal in the front right lamp connector
- Open ground for the front right lamp assembly
- Short to battery on the control wire, often from aftermarket lighting or an incorrectly repaired splice
- LED bulb fitted in place of a filament bulb, so the current is too low for the module to recognise
- Failed turn lamp driver inside the lighting control module
How to fix it
- Operate the indicator and watch all four corners so you know exactly which lamp is missing
- Remove the front right bulb, check the filament and inspect the socket for corrosion, burnt contacts or a loose spring terminal
- Fit a known good bulb of the specified type and see if the flash rate returns to normal
- Measure the voltage at the socket while the indicator is running, and check the ground side with a voltage drop test
- Disconnect the connector and check the control wire back to the module for continuity and for battery voltage that should not be present
- Renew a corroded socket or connector rather than trying to clean it, since the contact pressure is usually lost as well
- Consider the lighting module only when a good bulb, a clean socket and a proven harness still produce the code