U0105 Fault Code

Long Description

Fault code U0105 is a communication-related code that is logged when the onboard computer detects a loss of communication between the powertrain control module (PCM) and the fuel injection control module.

This electronic component is not to be confused with the mechanical fuel injector relay.

The fuel injection control module essentially controls the timing of each fuel injector in the engine. It receives information from the PCM and relays this to the various cylinders. This includes mainly the timing of each spray and the amount of fuel used for each cycle.

Issues with the fuel injector control module can cripple the performance of a vehicle due to its huge importance.

Some of the most common manufacturers to suffer from this code include Isuzu, GMC, Toyota, and Lexus.

Other Signs of This Problem

There will almost certainly be a huge number of significant signs of this issue if it is present. These can range in severity, but will all be noticeable.

The most obvious sign will be that the Check Engine light is illuminated on the dashboard.

In some cases, there will be an even more noticeable issue – the vehicle will crank but not start at all.

If the vehicle starts, it will likely display a lack of power, run rough, and even suffer from multiple misfires.

Be sure to look out for additional codes that this code can cause. These can include P0261 to P0284 and P0300 to P0308. These ranges can be extended if the vehicle has more than eight cylinders, such as a V10.

What Could Be The Problem?

Because this code is related to the communication of the various onboard systems, the cause will likely be electrical in nature. However, it is possible that there are some mechanical faults at work.

One of the most likely causes is an electrical issue between the PCM and the fuel injector control module. The controller area network (CAN) bus may be suffering from an open or short circuit in one of its connections. This can include a short to power or short to ground in either circuit.

It is also possible that the fuel injection control relay is faulty.

In addition to this, the PCM could be defective. However, it is rather rare that the PCM is the cause. It will also likely result in multiple various codes being logged.

Fixes

Fixing this fault code, like many other communication codes, will require electrical know-how as the cause is almost certainly electrical in nature.

The first thing to check should be the fuel injection control module. If it is determined to be faulty, it should be replaced.

The circuits need to be checked for electrical issues. Damaged wires and loose connections need to be repaired accordingly. This must be done for both CAN bus wires.

Any open or shorts to ground or power need to be fixed.

If the PCM is determined to be at fault, it needs to be replaced.

Seriousness

Fault code U0105 is a very serious issue. It can prevent the vehicle from even starting, essentially crippling it until the issue is resolved. Even if the vehicle is able to start, it will suffer massive losses in terms of performance and fuel consumption.

It is highly recommended to have this fault code fixed immediately.