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P3408 OBD-II Trouble Code: Cylinder 1 Deactivation/Exhaust Valve Malfunction

Check Engine Light

P3408 code definition

P3408 is the fault code for Cyl1 Exhaust Valve Ctrl Circ High. Cyl1 specifies that the issue is likely taking place in engine cylinder number 1.

What the P3408 code means

Late model vehicles with eight or more cylinders are designed so that half of the cylinders deactivate, by way of the ECM (engine control module) disabling the fuel injectors. This deactivation conserves fuel economy under light load operating conditions when all cylinders aren’t needed. The ECM (engine control module) receives information about operating conditions from various sensors, like the MAF (mass airflow) sensor, and commands the cylinders on or off based upon that data. When the ECM receives a signal from these sensors that is not within the reference range, it will set a code alerting you to the situation – in this case a code that tells you the problem is happening at the exhaust valve of cylinder 1.

What causes the P3408 code?

Cylinder deactivation can be affected by a number of problems, including:

  • A faulty MAP, MAF, or TP sensor
  • A bad valve lifter
  • Low oil pressure caused by sludge or dirt in oil passages
  • A short or damage in the wiring or connectors
  • Abnormal fuel pressure

On rare occasions, this problem may be caused by a faulty PCM or ECM, but this is typically not the case.

What are the symptoms of the P3408 code?

Cylinder deactivation malfunctions may cause the Check Engine light to come on. The vehicle will not be able to switch to V4 mode, and you may experience vibrations. If the issue is not addressed, you may notice a loss in fuel efficiency.

How does a mechanic diagnose the P3408 code?

Steps that may be done to diagnose P3408 include:

Common mistakes when diagnosing the P3408 code

The complete recommended diagnostic protocol should be carried out. If parts are replaced without testing all associated components, expensive, unnecessary repairs may result. Special attention should be paid to making sure the oil pressure is correct and cleaning out oil passages if it’s not.

How serious is the P3408 code?

This isn’t a code that will stop the vehicle from operating; however, over time additional damage could occur due to added stress on the engine from running in a way it wasn’t designed to run. It’s best to have a qualified mechanic assess the problem as soon as possible.

What repairs can fix the P3408 code?

A cylinder 1 deactivation malfunction may involve one or more of the following repairs:

Additional comments for consideration regarding the P3408 code

While your home scanner may give you a general idea of your vehicle’s problem, a qualified technician is equipped with tools that provide much more detailed information that can help in the diagnosis and repair of a cylinder deactivation circuit problem. The complex network of circuitry and sensors can make it difficult to pinpoint the issue without the proper tools and a considerable amount of time and effort. Consulting a professional can make the job faster and more efficient, and get your vehicle running smoothly and back on the road again.

Need help with a P3408 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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