Honda F-Can Malfunction: Causes and Fixes

Honda vehicles are equipped with several features to make driving a lot more interesting, smoother, and safer. The Controller Area Network is one of them with the fast controller area network (F-Can) being the most critical part of all CAN systems. The F-CAN is responsible for a couple of critical functions in the car. But when it has issues, your Honda braking system and other vital parts may not work. 

What is the F-Can and what causes it to malfunction? I’ll explain this in this article. Let’s get started.

What is F-Can and How Does it Work?

The Controller Area Network receives and shares pulsating indications that come in and out of the control modules. The Can uses two signal lines, namely CANL and CANH. It sends these signals to the ECM.

However, when the ECM can’t receive the signals for a long time, it detects an error, causing Diagnostics Trouble Code (DTC) to pop up. 

Whether it is Honda Odyssey, Civics, Pilot, or Accord, Honda models generally have two Controller Area Network (CAN) systems. The Fast Controller Area Network (F-Can) works at a faster speed of 33.33kbps. It essentially controls more important functions such as braking system (ABS), traction, vehicle stability, and so on.

The Body Controller Area Network (B-CAN), on the other hand, is a lower-speed Can. It regulates less critical activities such as blind spot indication, door locks, climate control, and so on. 

The two Can systems distribute information along several Engine Control Units (ECUs) in your car. However, the F-Can share information for real-time activities, including emissions and fuel data.

The CAN system contains the Gauge Control module. This module works on the Gateway Function principle to help decode information from F-Can to B-Can and vice versa. 

Why Does F-Can Malfunction?

Here are a few things that can cause your Honda F-Can not to work. Centrally, an F-Can issue is a problem of communication between the vehicle’s ABS and ECU. 

Faulty Engine Control Module (ECM)

Generally, once there is a problem with the engine control module, most parts of your vehicle will be affected. The ECM, as the name suggests, is a unit in your car that ensures optimal performance of the engine. It monitors and controls a couple of actuators on the car’s internal combustion engine. 

Once the system is damaged, a series of components in the controller area network (CAN) will become faulty. For example, the Vehicle Stability Assist will fail as the light turns on. It doesn’t matter if your Honda drives perfectly.    

Shorted or open VSA or GCM Harness

If the Vehicle Stability Assist or Gauge Control Module is open or has a short circuit, the fast controller area network will not work properly.

This is because the system will experience low resistance, causing accidental current diversion and contact of components.

Although it has a self-diagnostic function, a faulty Gauge Control Module will exhibit the same problem if it’s a short circuit. 

Failing Vehicle Stability Assist (VSA) Modulator Control Unit 

A failing VSA modulator control unit can also cause the F-Can to malfunction. The first symptom when the VSA modulator control system is that you’ll lose communication with the VSA. In the same vein, the cruise control won’t also work. This way, when you press the VSA button, nothing will happen. 

Poor electrical connection

Your Honda F-Can Vehicle Stability Assist poor electrical connection can cause the F-Can to malfunction. The Gauge Control Module circuit may also be poorly connected.

So, if there is a poor electrical connection or the circuit is damaged, the VSA or GCM light will give a false indication of a working system. Even if you turn on the VSA, the indicators may be off. 

How to Troubleshoot and Fix Honda F-Can Malfunction

There’s no one-size-fits-all technique to fix the F-Can malfunction. What you should do is look at each of the causes of a failing F-Can system above. Visually check the related issues, including the wiring connectors and harnesses. 

Inspect the damaged components, poorly connected wires, broken connectors, bent connector pins, pushed-out parts, and more. Regardless of the issue that causes the F-Can to fail, the check engine light will illuminate.  

As a helpful rule of thumb, before you troubleshoot or replace any faulty components, check all live data and record all freeze data. Take note of any onboard snapshots.

Depending on the error and error code, however, you can be in for a long haul when fixing an F-Can malfunction. It can take up to an hour of labor to be exact. 

  • Switch your Honda ignition on
  • Clear all DTC with Honda Diagnostic System (HDS)
  • Inspect DTCs with HDS or Temporary DTCS 

If the system indicates the error code, say DTC U0028, it’s time to update the PCM. There may be no updated PCM software. You can as well replace the old PCM with a new one. If the DTC U0028 indication disappears with a good PCM, you may need to replace the OEM PCM. At this time, the system should be fine and show no intermittent failure.

If the problem is the VSA modular control unit, take the steps above plus check for communication between HDS and VSA system and the connection at the GCM-PCM-VSA terminals.

If the HDS doesn’t communicate with the VSA, troubleshoot the DLC circuit by doing the following:

  • Switch the ignition switch off
  • With the HDS, jump the SCS
  • Unplug the VSA modulator control unit and the PCM connector 
  • Inspect if there’s continuity between PCM terminal connectors


What is the F-Can fault code for Honda Accord?

In most cases, the fault code for the F-CAN communication malfunction of your Honda Accord is ABS 86-01. Once this code error pops up, you’ll need to attend to it asap.

When the “F-CAN communication malfunction” error message comes up, the fault detected is the YAW rate sensor. What this means is that there’s an error on one of the connectors to the CAN wiring.   

What is the F-Can fault code for Honda Civic?

If you’re driving a Honda civic, the error code for F-Can failure is code U0122. The reason for the error code includes a faulty VSA modulator control unit, short VSA wiring harness, poor electrical connector or faulty Engine Control Module. 

How Much to Diagnose an F-Can Issue?

Most auto repair shops charge between $100 and $150 per hour. However, the labor cost may vary from one professional to another. Your location, car model, make of your vehicle, and engine type is factors that determine how much to pay.

Final Thoughts

An F-Can malfunction can throw any driver or car owner off balance. But you don’t have to worry any time you experience this issue and any of its symptoms. You may need to take a trip to the dealer. But again, a certified professional may be able to handle the issue.

As you know, an instrument cluster failure can be responsible. To avoid tampering with other critical components, get to a shop that deals exclusively in F-Can work. 

  • James Smith

    I'm James Smith, a car enthusiast and a content writer for Daily Car Tips. I have a passion for all things cars, from classic muscle cars to the latest electric vehicles. When I'm not writing about cars, you can usually find me tinkering with my car or checking out the latest automotive trends.

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