Fault code P266C is called “Rocker Arm Actuator “A” Position Sensor Circuit Low (Bank 2)” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P266C
OBD-II fault code P266C is a generic code that is defined as “low signal level in rocker (Bank 2) drive position sensor “A” circuit”. It is set when the Powertrain Control Module (PCM) detects that the “A” valve actuator (rocker) position sensor circuit in Engine Block 2 has a low signal level.
This code applies only to electronically actuated vehicles. These are vehicles whose engine oil pressure is adjusted electronically to change the valve timing. These systems are often called variable valve timing systems (VVT, VTEC and others).
In typical operation, a 12-volt signal is applied to all rocker arm solenoids when the ignition is on. The rocker actuator circuit is terminated when the PCM applies a ground pulse to the appropriate actuator at the exact interval.
The actuator will push up one end of the rocker arm, which is attached to the cylinder head by a stationary pivot. This movement causes the front end of the rocker arm to move downward, where it makes contact with the valve stem and opens it.
When the solenoid is de-energized, the actuator retracts and the valve closes. This action is repeated with each stroke of each cylinder of a running engine.
Newer cars use variable valve technology to allow more air flow through the engine at higher RPMs. This allows for greater performance over a wider range.
Some manufacturers are moving to an adjustable valve lift system that allows the valve to open wider. There are position sensors inside the variable lift rocker assembly, so the PCM control module can monitor what the assembly is doing.
If the PCM detects a low signal in the rocker actuator position sensor “A” circuit (Bank 2). Code P266C will be stored and the malfunction indicator light may illuminate.
Symptoms of vehicle malfunctions
The main signal that an error P266C has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- Other related fault codes may also be present.
- Reduced engine power.
- Increased fuel consumption.
- Uneven idling of the engine.
- Possible detonation in the engine, especially during acceleration.
- Sudden acceleration of the engine.
- Overall performance may decrease throughout the engine operating range.
This error is quite serious, as it can cause problems with the vehicle’s drivability. If code P266C is not corrected in a timely manner, serious mechanical damage to the engine may occur.
Factors that can cause this error code
The error code P266C can mean that one or more of the following problems have occurred:
- Rocker arm position sensor faulty.
- Problem with wiring or connectors in rocker arm position sensor circuit.
- Low engine oil level or pressure.
- Wrong type of engine oil.
- Sometimes a faulty PCM module is the cause.
How to fix or reset OBD-2 code P266C
Some suggested steps for troubleshooting and fix the error code P266C:
- Read all data and error codes stored in the PCM memory with an OBD-II scan tool.
- Reset the stored codes and test drive the vehicle.
- If error P266C returns, check connectors and wiring for damage or poor contact.
- Check the rocker arm actuator position sensor.
- Check the level, quality, type, and pressure of the engine oil.
- If the code is still active, the PCM probably needs to be flashed or replaced.
Diagnose and repair of problems
Before you begin the process of troubleshooting P266C, you should research the technical service bulletins (TSBs) for your particular vehicle. In some cases, this can save you a lot of time by pointing you in the right direction.
Make sure the engine is filled to the proper level with the recommended oil and that it is in good working order. If you have doubts about the integrity of the lubrication system, use a pressure gauge to check the pressure.
Low oil level and pressure in the engine are the main reasons why variable valve timing codes remain.
A detailed visual inspection should then be performed to check the wiring for obvious defects. Check all wiring and connectors associated with the rocker actuators as well as the rocker actuator position sensors.
Normal readings for wiring and connections should be 0 ohms of resistance. Wiring continuity checks should always be performed with all associated controllers disconnected from the circuit to prevent damage.
Resistance or lack of continuity indicates faulty wiring that is open or shorted. In this case, repair or replacement will be required.
If, after a complete check, all actuators, sensors, and circuits are OK, but the P266C error remains, the PCM may be faulty.
On which vehicles does this problem occur most frequently
Fault code P266C can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Ford
Fault code P266C can sometimes be found with other errors. The most common are the following: P266A, P266B, P266D, P266E.
