What does it mean?
B1670 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Right Trailer Tow Lamp Control Circuit High .
Symptoms
- Right hand trailer lamps do not work while the vehicle lamps are normal
- Trailer lamp fault message displayed when a trailer is connected
- Trailer indicator flashes at the wrong rate or not at all on that side
- The fault sets even with no trailer connected in some vehicles
- Intermittent operation that changes when the trailer plug is moved in the socket
Likely causes
- Corroded pins in the trailer socket, which is exposed to water, salt and road dirt
- Trailer lamp bulb on the right side burned out, or an LED trailer lamp drawing too little current
- Open circuit in the trailer harness between the module and the socket
- Trailer wiring incorrectly spliced into the vehicle lighting during an aftermarket towbar installation
- Short to battery on the trailer lamp control wire
- Damaged or crushed trailer harness where it is routed under the rear of the vehicle
- Failed trailer lamp output driver in the towing module or the body control module
How to fix it
- Test the vehicle with a known good trailer or a trailer test box so a faulty trailer is not mistaken for a vehicle fault
- Inspect the trailer socket pins for corrosion, bent contacts and water inside the housing, and clean or renew them
- Measure the voltage at the relevant socket pin while the corresponding lamp function is commanded on
- With the circuit off, check the control wire for continuity to the module and for battery voltage that should not be present
- Inspect the towing harness along its route under the rear of the vehicle for chafing and crushed sections
- Check any aftermarket towbar wiring, since incorrect splices are a frequent cause of these codes
- Repair or renew the socket and wiring, then confirm all trailer lamp functions with a test box before releasing the vehicle