P265B: B Rocker Arm Actuator Position Sensor Circuit Range/Performance Bank 1

What it means

The position sensor reading does not transition cleanly between the two valve lift modes for actuator B on bank 1.

At a glance

• Usually lights the check-engine light

How it works

The B rocker arm actuator position sensor tracks the switching position on bank 1. This range/performance code sets when its reading fails to transition as expected between lift modes, even if a signal is present.

Common causes

Most likely first.

1. Sensor signal drift after thermal aging
2. Worn lock pin reduces travel between modes
3. Sensor element aged beyond calibration window

Symptoms

• Check-engine light
• Reduced engine power or acceleration
• Rough running or engine misfire

How to diagnose it

1. Record freeze-frame data and compare live bank 1 B position readings with the actuator command to see when the transition is incomplete or out of range.
2. Inspect the B sensor connector and wiring on bank 1 for damage, loose pins, or intermittent contact.
3. Check engine oil level and condition, since poor oil supply can limit movement of the rocker arm mechanism.
4. Use the manufacturer's procedure to test sensor output through both commanded positions and compare it with specification.
5. If the electrical signal is sound, inspect the actuator travel and lock pin for wear or restricted movement.

Common fixes

• Repair a loose connector or damaged bank 1 B sensor wire.
• Correct low or contaminated engine oil and replace the oil and filter if due.
• Replace the B position sensor if its reading drifts outside the manufacturer's specification.
• Repair or replace the worn or restricted actuator mechanism if it does not complete its travel.

Can I keep driving?

Avoid heavy acceleration if the engine loses power or runs roughly, since bank 1 may not reach the intended valve lift mode. Stop if misfiring becomes severe or the check-engine light flashes.