What it means
The vehicle bus reports loss of communication with gear shift control module B. Shift-by-wire requests for park/reverse/drive coordinated through this node are no longer answered.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
Gear shift control module B handles part of the electronic gear-selection system and exchanges requested gear and status messages with other modules. This code sets when the vehicle network stops receiving expected messages from module B, so Park, Reverse or Drive selection coordinated through it may not work.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame data, noting whether the fault appeared during a shift and whether other gear-control or network codes are present.
- Check the displayed gear against the selector position and confirm whether Park, Reverse and Drive requests are recognized; do not force a shift if the display or engagement is uncertain.
- Inspect module B's connector and harness for damage, water, corrosion or a loose connection, especially near areas disturbed by recent repairs.
- Check the module's specified power and ground, then test its network wiring for opens, shorts or poor connections using the wiring diagram and manufacturer procedures.
- If the supply and network test correctly, follow manufacturer diagnostics to determine whether module B or a related gateway has failed.
Common fixes
- Repair a loose, corroded or damaged connector at gear shift control module B.
- Repair an open or short in the network wiring to module B.
- Restore module B's specified power or ground by repairing the identified feed, fuse or ground fault.
- Repair a gateway routing fault if manufacturer diagnostics confirm it is preventing messages from reaching module B.
- Replace module B only after power, ground, network wiring and gateway operation are verified.
Can I keep driving?
Do not drive if the vehicle will not reliably select or hold the requested gear, or if the gear display disagrees with the actual response; arrange recovery. If shifting remains normal, limit driving and avoid situations requiring precise gear selection, because the fault can progress to loss of drive or Park recognition.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.