Technical Description of OBD-II Trouble Code
Cylinder Deactivation System Bank 1
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is commonly found in many OBD-II vehicles, including Honda, Dodge, Ram, GMC, Chevrolet, Chrysler, Pontiac, etc.
A stored code P3400 indicates that the powertrain control module (PCM) has detected an abnormality in the cylinder deactivation system for engine bank one.
Bank 1 refers to the engine bank that contains the number one cylinder. The location of the number one cylinder varies depending on the make and model of the vehicle. Consult the service manual or an alternate source of vehicle information to determine the location of the number one cylinder for the specific vehicle – never make assumptions in this regard.
Cylinder deactivation (also known as variable displacement) systems are designed to conserve fuel. They are primarily used in vehicles equipped with engines that have more than eight cylinders.
Under certain driving conditions, when full engine power is not required, the cylinder deactivation system disables specific cylinders to save fuel.
The variable valve timing solenoids are used to close the intake and exhaust valves for the deactivated cylinders. This serves two purposes: reducing vibration and improving the smoothness of cylinder deactivation operation, and compressing the trapped exhaust gases to provide better overall engine balance.
In addition to closing the valves on the deactivated cylinders, the cylinder deactivation system also stops fuel flow to those cylinders. There is usually no noticeable loss of power or torque when the cylinder deactivation system is active.
If the PCM is unable to activate the cylinder deactivation system for engine bank one, or if it detects that the system has inadvertently become active, a code P3400 will be stored and the malfunction indicator lamp (MIL) may illuminate.
Cylinder Deactivation Engine:
What is the severity of this DTC?
In addition to potentially reducing fuel efficiency, cylinder deactivation problems can lead to serious engine failure. The P3400 code should be addressed promptly and considered severe.
What are some of the symptoms of the code?
Symptoms of a P3400 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P3400 troubleshooting steps?
Note: There are known technical service bulletins (TSBs) for certain Honda & Acura vehicles related to this code. They are Honda TSB 11-033, Honda TSB 13-031, and Honda TSB 13-055.
Components critical to the operation of the cylinder deactivation system often rely on engine oil pressure. Therefore, diagnosing any cylinder deactivation codes should begin by ensuring that the engine has the correct oil level and that the oil pressure is within specifications. If there are doubts about the actual oil pressure, a manual oil pressure test should be conducted.
To accurately diagnose a code P3400, a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle information will be necessary. If there are concerns about engine oil pressure, a manual oil pressure gauge will also be required.
A reliable source of vehicle information may provide relevant technical service bulletins (TSB) that can assist in the diagnosis. It should also offer diagnostic flow charts, wiring diagrams, connector face views, connector pin-out charts, and component testing procedures/specifications. This information is essential for reaching a correct diagnosis.
Always disconnect controllers before testing system circuits with the DVOM to avoid damaging the controllers.
Once engine oil pressure has been confirmed to be within specifications and a visual inspection of related connectors and wiring has been performed, connect the scanner to the vehicle’s diagnostic port. Retrieve all stored codes and related freeze frame data. It may be helpful to write down this information for later reference. Clear the codes and test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode, it indicates that an intermittent code is present. The conditions that caused the code may need to worsen before a successful diagnosis can be made. If the code is reset, locate the appropriate diagnostic flow chart in the vehicle information source and follow it to reach a conclusion.
Use the DVOM to test the individual variable valve timing solenoids. Solenoids that do not meet the manufacturer’s specifications should be considered defective.
