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  • The powertrain control module (PCM) will register a P3400 trouble code when the cylinder fails to deactivate upon the computer’s command.
  • This code is set because of low oil pressure/level, faulty valve timing control solenoid/s, and shorted deactivation circuits.
  • If this code is present, your vehicle can exhibit symptoms like decreased fuel economy, poor engine performance, and logged misfire-related codes.

Have you noticed a sudden decrease in your vehicle’s engine performance? You’ll need to use an OBD-II scanner to get a better understanding of your vehicle’s issues. One of the diagnostic trouble codes you might encounter is P3400. Here’s everything you need to know about code P3400.

What Does the P3400 Code Mean?

P3400 is the diagnostic trouble code for “Cylinder Deactivation System Bank 1.” A P3400 code indicates that your vehicle’s powertrain control module (PCM) perceives a potential problem with your cylinder deactivation system bank 1. Vehicles that commonly have this fault are Honda, Dodge, Ram, GMC, Chevrolet, Chrysler, and Pontiac

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A P3400 code indicates that your vehicle’s powertrain control module (PCM) perceives a potential problem with your cylinder deactivation system bank 1. Bank 1 refers to the engine bank that contains the number one cylinder. The location of the number one cylinder is different for some makes and models. It’s best to consult your vehicle’s repair manual for the location of your number one cylinder. Other diagnostic codes may be present alongside P3400 in some cases.

cylinder head of a car
The P3400 code indicates that your vehicle’s PCM perceives a potential problem with your cylinder deactivation system bank 1.

Code P3400 reflects the results of a rationality check performed by the PCM each time the cylinder deactivation is engaged. Airflow, throttle angle, and engine speed should reflect a calibrated difference. If the PCM engages cylinder deactivation but the rationality check indicates cylinder deactivation didn’t happen, code P3400 is set.

For just one example, GM describes the P3400 condition as: MAF Sensor / MAP Sensor / Throttle Position not within the calibrated range with Cylinder Deactivation System Active.

Note:  The definition of P3400: Cylinder Deactivation System Bank 1 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition. 

What are Possible Causes of P3400?

Several factors can trigger the P3400 code. Here are some of the most common causes:

  • Engine oil level or pressure is low
  • Faulty valve timing control solenoid/s 
  • Cylinder deactivation circuit/s may be open or shorted
  • Defective PCM or PCM programming error
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What are the Common Symptoms of the P3400 Code?

If your PCM is storing a P3400 code, your vehicle may show some of the following symptoms:

  • Illuminated warning lights (e.g. check engine light)
  • Reduced fuel efficiency
  • Decreased engine performance 
  • Other cylinder deactivation codes 
  • Engine misfire codes
valve timing solenoid
Faulty valve timing control solenoid/s can trigger the code P3400.

How to Diagnose the P3400 Code

The P3400 code must be resolved as soon as possible to avoid complications down the line. We recommend having a professional mechanic check your vehicle if you don’t have the required auto repair experience and skills. However, if you want to diagnose the code yourself, we’ve included an informational video down below to help you get started.

How to Fix the P3400 Code

There’s no magic bullet for resolving OBD-II trouble codes because the recommended fixes are different for every make and model. Hiring a professional mechanic to diagnose and fix your P3400 code may be the best course of action if you don’t have any auto repair experience.

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However, if you want to flex your DIY muscles, you should first look up the most common P4300 code problems for your specific vehicle. A repair manual or database may contain the information you need to determine the underlying causes for your P3400 code. There are plenty of online auto repair resources available to help you fix your diagnostic trouble codes. We recommend subscribing to ALLDATA for your diagnostic repair needs.

Keep in mind that different car manufacturers have their own set of repair instructions for their vehicles. What works for a Honda may not work for a Pontiac. To avoid mistakes, stick to your vehicle’s repair manual when diagnosing trouble codes.

Other Notes About P3400

A set code doesn’t necessarily imply that a specific part is defective. For example, P3400: Cylinder Deactivation System Bank 1 doesn’t always indicate an issue with the cylinder deactivation system.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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