What it means
The gear shift control module B communication circuit reports a communication circuit condition. Shift command exchange is impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Gear shift control module B exchanges shift-related messages with other control modules over the vehicle communication network. This code indicates that communication on the module B circuit is disrupted, so shift commands or status may not arrive reliably.
Common causes
Most likely first.
- Communication lost
- Wiring fault
- Gateway module routing CAN messages incorrectly
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and scan all accessible modules to see whether module B is offline or other network faults are present.
- Check whether the scan tool can communicate with gear shift control module B and note any lost-communication codes in other modules.
- Inspect module B connectors and the network wiring for looseness, corrosion, chafing, or water damage.
- Check module B power and ground, then test the communication circuit and network condition using the manufacturer's procedures.
- If the wiring and module connections pass, check whether the gateway is routing the relevant messages correctly before condemning module B.
Common fixes
- Secure or clean a loose or corroded module B connector.
- Repair damaged communication wiring to gear shift control module B.
- Restore the module's power or ground connection if faulty.
- Correct a verified gateway routing or configuration fault.
- Repair or replace module B only after network and power checks isolate it.
Can I keep driving?
The transmission may shift harshly, delay shifts, or enter a limited gear mode if module B cannot communicate. Avoid long trips and stop if the vehicle cannot select or hold gears reliably.
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.