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DTC codes / P26xx · Computer and output circuits / P264C

P264CA Rocker Arm Actuator Position Sensor Circuit Low Bank 1

P264C indicates that the powertrain control module has detected an abnormally low voltage signal from the rocker arm actuator position sensor on bank 1, which is the side of the engine containing cylinder number one. The sensor reports the physical position of the rocker arm actuator, and a low signal means the circuit is shorted to ground, the sensor has failed, or the actuator is stuck in a position that produces a low reading.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Rough idle or misfire that may feel like a slight shake at stoplights
  • Reduced engine power or a limp-home mode triggered by the control module
  • Poor fuel economy as the engine management system defaults to a less efficient operating strategy
  • Intermittent hesitation during acceleration when the actuator fails to respond to commands
  • A noticeable tick or rattle from the valvetrain area on bank 1 if the actuator is mechanically stuck

Common causes, most likely first

  1. A failed rocker arm actuator position sensor that internally shorts to ground
  2. Damaged or chafed wiring in the sensor circuit, often where the harness bends near the valve cover
  3. Corroded or loose electrical connector pins at the sensor or at the control module
  4. A mechanically stuck rocker arm actuator that cannot move to the position the sensor expects
  5. Oil sludge or debris obstructing the actuator, preventing proper movement and causing a low sensor reading
  6. A short to ground in the signal return circuit between the sensor and the control module
  7. A rare internal fault in the powertrain control module driver circuit for the sensor

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, then record freeze-frame data to confirm the fault conditions
  2. Visually inspect the sensor connector and wiring harness on bank 1 for chafing, corrosion, or loose pins
  3. Measure sensor reference voltage and signal voltage with a digital multimeter, comparing readings to the manufacturer's specification
  4. Perform a wiggle test on the harness while watching live sensor data to catch intermittent wiring faults
  5. Check the rocker arm actuator for mechanical freedom and inspect for oil sludge or debris that could restrict movement
  6. If the sensor signal remains low with a known-good sensor and wiring, test the control module circuit or substitute a known-good module for diagnosis
  7. Replace the faulty sensor or repair the wiring, clear the codes, and verify the repair with a road test and live data review

What a low sensor signal really tells you

  • A low signal code does not automatically mean the sensor is bad; a shorted signal wire or a poor ground connection can produce the same low voltage reading at the control module.
  • Technicians often overlook oil sludge on the actuator, which can physically restrict movement and cause the sensor to report a low position even when the electrical circuit is healthy.
  • Intermittent low signals that appear only when the engine is hot often point to a failing sensor that breaks down with heat, not to a wiring fault.
  • Some vehicles use a shared reference voltage for multiple sensors, so a short in another sensor on the same circuit can drag down the rocker arm actuator position signal.
  • After replacing the sensor, a relearn or adaptation reset may be required before the control module will accept the new sensor signal and turn off the light.

Can I keep driving with P264C?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or sustained high-speed driving because the engine may enter a reduced-power mode. If the check engine light begins flashing or you feel a strong misfire, stop driving and have the vehicle towed to prevent catalytic converter damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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