What it means
The signal from park position sensor or switch B is outside the expected performance range on the high side.
At a glance
- Usually lights the check-engine light
How it works
The transmission control module reads park-position switch B to confirm selector position. This code sets when the B signal is above the expected range, indicating a high-side performance problem.
Common causes
Most likely first.
- Park position sensor or switch B fault
- Damaged wiring or poor connector contact
- Sensor misalignment or mechanical wear
- Fault in the transmission control module input circuit
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
- Read freeze-frame and transmission live data to identify when the B signal went high and what selector position the module reported.
- With the vehicle securely parked, observe the reported B state while moving the selector through each position.
- Inspect switch B and its connector for misalignment, corrosion, loose pins, or wiring damage that could allow an unwanted high signal.
- Use the wiring diagram to test the B signal for a short to supply voltage and check its power and ground connections.
- If the harness is sound, test switch B across its operating range and verify the module input against the manufacturer's specification.
Common fixes
- Secure or clean a loose or corroded switch B connector.
- Repair wiring shorted to a voltage source or damaged near switch B.
- Correct park-position switch B alignment if applicable.
- Replace switch B if its output remains high when it should change.
- Repair the transmission control module input circuit if tests isolate the fault there.
Can I keep driving?
Limit driving and avoid relying on the indicated selector position if shifts are delayed, harsh, or unpredictable. Stop and arrange a tow if the transmission slips or enters a fixed gear, since continued driving can cause further damage.
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.