What does it mean?
B1647 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Rear Right Turn Lamp Control Circuit Low .
Symptoms
- Rear right indicator does not flash, or remains permanently on
- Rear lighting fuse blows again shortly after it is replaced
- Bulb out warning together with an abnormal flash rate
- Other lamps in the same cluster flicker or glow faintly because of corrosion
- The fault appears after rain or over rough road surfaces
Likely causes
- Short to ground in the rear right lamp control wire, commonly where the loom passes a body grommet or a sharp panel edge
- Water sitting in the rear right lamp cluster, corroding the holders and bridging the circuit board tracks
- Trailer or towing wiring connected into the rear lamp circuit and adding load or a short
- Bulb of the wrong type or a bulb base making contact with the lamp housing
- Harness crushed under the load floor or by luggage compartment trim
- Shorted rear lamp driver inside the lighting control module
How to fix it
- Take out the rear right cluster and check for standing water, corroded holders and heat marks on the circuit board
- Unplug the cluster and see whether the code still sets, which tells you if the fault is in the lamp or in the harness
- Measure resistance between the control wire and ground with the connector disconnected; a low value confirms a short to ground
- Trace the loom through the body grommet and along the quarter panel, looking for chafed insulation and crushed sections
- Temporarily disconnect any trailer wiring or added accessory to rule it out
- Repair the wiring with sealed joints, dry the housing and renew the seal so water cannot get back in
- Replace the lighting control module last, only if the output stays low with the harness unplugged