What does it mean?
B1661 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Front Fog Lamp Control Circuit Open .
Symptoms
- Neither front fog lamp works when the switch is operated
- Fog lamp indicator in the cluster comes on but there is no light output
- No relay click is heard from the fuse box when the fog lamps are selected
- Poor visibility in fog and heavy rain because the low mounted beam is missing
- The fault appeared right after front end body work or a bumper removal
Likely causes
- Both front fog lamp bulbs burned out, which is common because they are usually switched on together
- Fog lamp connector left unplugged after bumper, grille or front panel work
- Broken control wire behind the bumper, where the loom is exposed to stones, salt and vibration
- Corroded terminals in the fog lamp pigtail so the contact is lost even though the plug looks connected
- Open relay coil or a relay removed from the fuse box
- Module configured for fog lamps on a vehicle that is not fitted with them, or after a control module was replaced with a different specification
- Open output driver in the lighting control module
How to fix it
- Check the fog lamp fuse and relay, and swap the relay with an identical one to test it
- Inspect both fog lamp bulbs, since both being burned out will give exactly this pattern
- Verify that the fog lamp connectors are actually plugged in and locked, especially if the bumper has recently been off
- Command the fog lamps on with a scan tool and measure the voltage at the lamp connector
- With the circuit off, check the control wire for continuity between the module and the lamp connector to find the open
- Confirm that the vehicle configuration matches the fitted equipment when a control module has been replaced or coded
- Repair the broken wire or corroded terminal, refit correct bulbs, and treat the module as the last suspect