Error Code P3400 is defined as Cylinder Deactivation System Bank 1, indicating performance issues with the said component.


During starting or idling, when the vehicle is working under heavy loads, the engine will operate in V* mode using 8 cylinders. However, when driving conditions are light, the engine will automatically downgrade its operation by deactivating 4 of the 8 cylinders, changing from V8 to V4 mode.

The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) will determine the driving conditions for the vehicle, using the data it receives from the MAF (Mass Airflow) sensor, MAP (intake manifold absolute pressure) sensor, and TP (throttle position) sensor.

The PCM will instruct the deactivation solenoids of the cylinders to commence the deactivation process. This will then deactivate the cylinder 1, cylinder 4, cylinder 6, and cylinder 7, by restricting the flow of oil to the valve lifters of these cylinders, preventing the intake valves and exhaust valves from working. The vehicle can’t operate under V4 mode if these sensors are in wrong range.

When the PCM determines that the measured values for the MAF sensor, TP sensor and MAP sensor are outside the predetermined range for V4 mode, then the Error Code P3400 will register, activating the Check Engine light as well.

Common Symptoms

As said earlier, this code activates the Check Engine light, while registering the code to the vehicle’s memory system. Another common symptom is that it causes the engine to vibrate.

Possible Causes

There are many causes for this code to appear, some of the most common possible causes include:

  • Open or short in cylinder deactivation solenoid harness
  • Defective cylinder deactivation solenoid
  • Bad electrical connection in cylinder deactivation solenoid circuit
  • Faulty MAF sensor
  • Faulty TP sensor
  • Faulty intake control manifold absolute pressure sensor
  • Restrictions or clogging in the oil passages
  • Defective lifters
  • Poor oil pressure on the lifters

How to Check

To diagnose this code, technicians usually start by making sure the engine oil levels are correct. Also, they make sure the engine has the correct oil pressure.

To collect the diagnostic trouble codes stored in the PCM, they will use an OBD-scanner.

If the PCM has other stored deactivation and oil pressure error codes, they should be diagnosed first.

The scanner will also be used to clear the codes.

Next, they will test the cylinder deactivation solenoid #1 by actuating it with a scan tool. A solenoid that is properly working will vibrate and make a clicking noise. A bad one will not. Thus, technicians will check the oil passages and look for signs of debris, and clean the oil passages as necessary, if not replace the solenoid.

If the cylinder deactivation solenoid #1 is working properly, the cylinder deactivation solenoid #7 will be the next one that will be checked.

The same process will be completed – the technician will test the cylinder deactivation solenoid # 7 by actuating it with the scan tool. It will vibrate and make a clicking noise. If it’s not working properly, then the oil passages will be checked for debris and must be cleaned or replaced if necessary.

If the cylinder deactivation solenoid #7 is working properly, inspect the oil passages to the lifter.

Oil passages that are restricted or clogged must be cleaned, as necessary. The engine block may have to be disassembled if the whole engine is restricted.

Lifters must be replaced as well if the oil passages are still restricted.

How to Fix

Here are common fixes for this code:

  • Replacement of cylinder deactivation solenoid #1
  • Replacement of cylinder deactivation solenoid #7
  • Clearing debris and dirt out of cylinder deactivation solenoid
  • Clearing debris and dirt off of lifter oil passages
  • Replacement of lifters in engine
  • If the whole engine is packed with dirt and sludge, then it is necessary to disassemble to entire engine to clean it properly

If this code is present, the vehicle will run on all 8 cylinders, rather than 4, which means it will consume more fuel and increase engine emissions.

Though Error Code P3400 may not generally be considered as a serious problem, it is important to fix it as soon as possible.