What it means
The signal from park position sensor or switch B is outside the expected performance range on the low side.
At a glance
- Usually lights the check-engine light
How it works
The transmission control module uses park-position switch B to help confirm the selector’s position and manage transmission operation. This code sets when the B signal is lower than expected or performs outside its acceptable low-side range.
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 data and transmission live data to see when the B signal went low and whether the selector position was reported correctly.
- With the vehicle safely parked, compare the reported park-position B state as the selector is moved through its positions.
- Inspect switch B, its connector, and nearby wiring for misalignment, corrosion, loose pins, or damage that could pull the signal low.
- Check the B circuit and its power, ground, and signal connections for opens, shorts, or poor contact using the vehicle wiring diagram.
- If the wiring checks out, test switch B through its operating range and check the transmission control module input against the manufacturer's specification.
Common fixes
- Reconnect or clean a loose or corroded switch B connector.
- Repair damaged wiring or a poor ground in the B circuit.
- Correct park-position switch B alignment if it is adjustable.
- Replace a faulty park-position switch B.
- Repair the transmission control module input circuit if testing confirms a fault.
Can I keep driving?
Avoid driving if the transmission shifts harshly, slips, or cannot reliably identify the selected position; arrange a tow if control is unpredictable. Continued driving can worsen transmission damage or leave the vehicle unable to shift safely.
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.