P3400 Fault Code

Long Description

Fault code P3400 is logged when the powertrain control module (PCM) has detected an issue with the cylinder deactivation system for the first bank of the engine.

Cylinder deactivation systems were implemented in modern engines to help reduce the amount of fuel consumed by the engine when full power is not required. This can be at a standstill or while cruising at lower speeds.

This code is only applicable to engines with more than one bank, most commonly V-shaped engines. This is because a single bank engine like an inline-4 cannot deactivate and still function.

Some of the most common manufacturers to suffer from this code are Chevrolet, Honda, Dodge, and Chrysler.

Other Signs of This Problem

This code may not have the most noticeable symptoms because it can mean the engine is running without deactivating the cylinders in question. This would typically result in normal driving operation. This makes it important to pay attention to small changes in the vehicle’s performance.

One of the most obvious signs will be the presence of the Check Engine light on the dashboard.

Another fairly obvious symptom will be increased fuel consumption. This is because the cylinder deactivation system is meant to save fuel. If it is not functioning properly consumption should be noticeably increased compared to when it is working.

It is also very likely that other cylinder deactivation codes will be logged because P3400 is a broad code. Be sure to look out for codes ranging from P3401 to P3429. These can also help pinpoint the cause of this code.

What Could Be The Problem?

Because the cylinder deactivation is a relatively closed system, most possible causes will be found within.

One of the most likely causes is an electrical issue within the system circuit. These can be the result of loose connections or damaged wires, as well as short circuit conditions.

Another potential cause is a faulty valve timing solenoid. These are required to close the valves in the engine, cutting off the air intake and exhaust lines.

Adding to this, engine oil that is too low or circulating at too low of a pressure can also result in this code being logged.

In rare cases, a faulty PCM can be the culprit. However, this is typically accompanied by a number of additional fault codes being logged.

Fixes

As with all fault codes, the first step in fixing this issue is determining where the cause is. This is especially true given this code can be caused by either an electrical or mechanical issue.

Checking the engine oil is one of the simplest steps to take in fixing this problem. Oil that is low or contaminated should be changed with the correct oil.

The circuit for the cylinder deactivation system needs to be checked for any electrical faults and fixed accordingly.

The valve timing control solenoids also need to be checked. Damaged or otherwise defective solenoids need to be replaced.

If it is determined that the PCM is faulty, this will require a reflash from the manufacturer or replacing the control module itself.

Seriousness

Fault code P3400 is not a very serious code. These systems are added on top of a perfectly functioning engine, so if they fail they do not have an inherent effect on the engine’s performance.

It is a good idea to have this code fixed within a few days to prevent unnecessary fuel consumption issues. There may also be more serious issues causing this code.