5 Common Problems with Freightliner M2 Bulkhead Module?

A complex system of various modules works in tandem to make the Freightliner m2 truck function properly. And a primary electrical control unit or bulkhead module oversees this cooperation. So, all Freightliner drivers need to be aware of the issues that might affect this important piece of equipment.

The most typical Freightliner m2 bulkhead module problems involve faulty wiring and connections. When this happens, the bulkhead cannot collaborate with the signals it receives. As a result, it becomes hostile to scanners and unresponsive to drivers’ inputs. 

A malfunctioning bulkhead module can confuse the driver on the road with incorrect fault codes. However, acquiring knowledge about the BHM will make such situations less difficult for you.


5 Most Common Issues with Freightliner M2 Bulkhead Module:

The bulkhead module is the central controller of your truck’s Slave Modules. It establishes this control by receiving, processing, and conveying data signals. 

Data cables and wire harnesses are used to carry out the activities. So, issues with these two can cause a BHM malfunction on your Freightliner.

1. Misfiring Harnesses

Several harnesses connect the bulkhead module to the rest of the Slave Modules and other components. These connections allow the BHM to control and collaborate among the different parts of your truck’s electrical system. 

So, if these harnesses misfire or suffer from poor connection, multiple systems in your truck might act up.

Four harness connections are of major importance to your truck’s BHM. These are the chassis, engine, and two front wall harnesses. Three dash harnesses connect to the cab side.

Misfiring harnesses will generate unreasonable fault codes. As a result, the driver might get confused about the internal condition of the vehicle. 

You may have to replace a faulty harness to prevent misfiring. Dirt, corrosion, power spikes, and other factors can cause this damage.

The replacement cost of harnesses will include expert inspection and labor costs. So, you may have to spend over 150$ if you cannot solve the problem yourself.

2. Datalink Issues

Datalinks are the connections between various components, switches, and sensors in your truck that permit signal transfers at incredibly fast rates. 

These links reduce the number of wiring you need and make an individual component diagnose and report its issues on its own to the central computer system of your vehicle.

When the bulkhead module is compromised, the data link signals lose sync with the main control unit. As a result, an OBD scanner or other diagnostic computer cannot connect properly with your Freightliner. 

Reprogramming your bulkhead module might be the only option in this case. Sometimes, you need to get a new module if the previous one proves to be beyond repair. Expect costs around 150-200 dollars.

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3. J1939 and J1708 Code Due To Shorted Wire

The J1939 and J1708 codes are the datalinks BHM uses to report the faults it discovers in the system. You can see the reports via ServiceLink- a software tool for scanning Freightliner problems.

If your truck is suffering from harness misfiring and data link issues, you might have trouble connecting your laptop to the vehicle in the first place. And when you manage to connect somehow, the codes will be all over the place.

However, if those two (misfiring or datalink) aren’t the issue, you can easily connect the ServiceLink and still view your scanner’s J1939 and J1708 fault codes. In this case, the most probable diagnosis is a shorted wire.

The BHM collaborates input and output commands between several components of the car. So, a shorted wire from the ignition switch, cigar lighter, horn, etc. 

This will trigger the  BHM to generate a fault code. Finding and repairing the shorted wire will fix the problem in this case.

4. BHM Awake Mode Issues

The BHM, CHM (Chassis Module), and ICU (Instrumentation Control Unit) become simultaneously awake when either one of these systems is activated. This happens when you turn on the ignition key.

However, you may sometimes find that the BHM had been awake even after you turned off the ignition. This means your car has lost valuable battery power in the meantime. 

It’s like you had parked the Freightliner at a stop, went inside for refreshments, and returned to find your battery drained.

The most probable reason is that you have an ignition switch error. Whenever the ignition switch isn’t in the ‘Off’ position for certain, the BHM goes into awake mode.

In other words, the BHM can assume only two positions for your ignition. It’s either surely ‘OFF’. If it slightly deviates from that position, the BHM considers it ‘ON’ and awakes.

So, always ensure the position is perfectly off before leaving the car. And if that doesn’t solve the problem, replace a faulty ignition switch.

5. Numerous Output Issues

When the driver provides input, the signal goes to BHM. The module analyzes the signal and creates an appropriate output.

BHM does this for many components in your truck. These include the A/C clutch, Backup lights and alarms, horn, cigar lighter, clutch, parking brake, low air pressure warning system, and more.

A malfunctioning BHM can bring all these systems down. You will experience multiple components ceasing to function at the same time. And that is one of the surest signs that your BHM is damaged or needs replacement.

Replacing a BHM isn’t hard. You can find a detailed step-by-step guide in your truck’s manual. However, the component itself is quite expensive. A Freightliner M2 Bulkhead Module will cost no less than 2000$.

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How To Prevent BMH Issues On Your Freightliner m2?

How To Prevent BMH Issues On Your Freightliner M2

The BHM replacement is quite a costly repair for your truck. So, the best practice is to prevent something like that from happening in the first place. 

Freightliner m2 Bulkhead modules are tough, to begin with. So, if you follow a few simple maintenance rules, it will stay good for a long time- 

  • Regularly inspect the condition of your bulkhead module
  • Check for corroded wires and connections and get rid of them. Faulty connections can cause power spikes and destroy your bulkhead module 
  • Maintain a cleaning routine for your car. Dirt and debris can accumulate internally after long trips on highways. These can seriously impact the health of your bulkhead module. 
  • Replace all malfunctioning harnesses as soon as possible.

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Is Reprogramming Freightliner BMH Possible? 

You can connect a diagnostic laptop to your Freightliner and program the BHM using Diagnostic link 8. Your laptop should have an internet connection for downloading purposes. 

When you first access the BHM data and view it on the Standard tab, you will encounter several warning codes. Erase all the codes and other data. Afterward, click ‘connect to the servers’ to download new data. You will need to input your Vehicle Identification Number for this process. 

Like any other software installation, you will click ‘Start’ for the downloaded data to install. And When the process completes, select ‘Finish.’

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You now have adequate knowledge to deal with BHM issues on your Freightliner. Nonetheless, there can still be some questions. Feel free to ask.

Can I continue driving my Freightliner with a faulty m2 BHM?

Continuing with a damaged BHM might not be possible if multiple systems of your truck are down. In harness and datalink cases, you won’t be able to connect the diagnostic laptop. So, the answer is negative. 

How much does it cost to replace the BHM? 

Freightliner’s m2 bulkhead modules cost around 2000$. The good thing is these things don’t damage easily. Often BHM problems involve harnesses, datalinks, or shorted wires. You can manage these repairs within 200$. 

Where can I find the BHM in my Freightliner? 

Open the hood of your truck. Look at the steering column. You will see the bulkhead module slightly below it on the front wall at the engine side. 

Do All Freightliners have BHM? 

No. Freightliners made before 2016 didn’t have bulkhead modules. The necessity for the BHM arose because manufacturers were trying to reduce the overwhelming wiring in the trucks. At the same time, they were trying to make truck systems faster and smarter. 


Freightliner m2 bulkhead module problems can frustrate a driver on the road. However, losing patience will not help your situation. The correct strategy is to use reasoning and knowledge to find the exact source of the problem. 

If you have no choice but to replace the BHM on your truck, follow proper safety protocols. Always disconnect the battery leads before you start working. 

Using the proper tools is beneficial both for you and your car. Lastly, take the best care of your BHM, so you don’t have to go through a replacement that costs thousands of dollars.

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