What it means
The position sensor or switch of transmission range control channel B reports a circuit low condition. The TCM cannot verify the actuator position reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The transmission range control B position sensor or switch reports the B-channel mechanism's position to the transmission control module. This code sets when the B signal voltage is lower than expected, so the module cannot reliably confirm position.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal short in position sensor
- Connector pins corroded - high contact resistance
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
- Record freeze-frame data and review live data for commanded range and B-channel position to see when the low reading occurs.
- Compare the shifter selection with the range reported by the transmission module and note any mismatch.
- Inspect the B sensor connector and signal-wire harness for corrosion, damaged insulation, loose pins, or contact with ground.
- Test the B signal wire for a short to ground and check connector terminal condition using the vehicle wiring diagram.
- Check the B position sensor or switch output against the manufacturer's specification before replacing parts.
Common fixes
- Clean and secure corroded B-channel connector terminals.
- Repair the B signal wire where it is shorted to ground.
- Replace the B position sensor if its internal signal remains low.
- Clear the code and confirm B-channel readings agree with the selected range.
Can I keep driving?
Avoid driving if the transmission misreads the selected range, shifts harshly, or enters limp mode, because gear engagement may be unreliable. If it shifts normally, limit use until the B-channel low signal is diagnosed.
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.