What does it mean?
B1648 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Rear Right Turn Lamp Control Circuit High .
Symptoms
- Rear right indicator stays dark while the front indicator still flashes
- Rapid flash rate and a lamp failure warning in the cluster
- Function comes back for a while after the bulb is turned or the cluster is refitted
- Hazard flashers show the same lamp missing
- Trailer lighting, where fitted, works incorrectly on that side
Likely causes
- Rear right indicator bulb burned out or loose in its holder
- Corroded holder contacts or a cracked track on the rear lamp circuit board
- Open circuit in the rear harness, often in the flexing section that runs into the tailgate or boot lid
- Missing or high resistance ground for the rear right lamp assembly
- Short to battery on the control wire from a poorly installed trailer socket or accessory
- LED lamp or LED conversion drawing too little current for the module to recognise
- Faulty rear lamp driver inside the lighting control module
How to fix it
- Operate the indicators and confirm exactly which lamp is not working
- Remove the bulb, inspect the filament, and check the holder contacts for corrosion or lost spring tension
- Fit a known good bulb of the correct type and see whether the flash rate normalises
- Measure the supply voltage at the holder with the indicator running, then carry out a voltage drop test on the lamp ground
- Unplug the cluster and check the control wire for continuity to the module and for battery voltage that should not be there
- Renew the holder, the lamp cluster or the damaged harness section, and pay attention to the wiring inside the tailgate flex loom
- Replace the control module only when a good lamp and clean wiring still leave the code active