Freightliner Fault Code List & Repair Guide

Freightliner is one of North America’s most famous medium- and heavy-duty truck manufacturers. Thousands of fleets across the U.S. and Canada depend on Freightliner trucks such as the best-selling Freightliner Cascadia to keep their business moving. With that in mind, downtime is a major concern.

If your Freightliner truck is down and stuck in the shop, don’t fret. When something goes wrong, the truck’s onboard computer generates a fault code to help technicians identify the issue and troubleshoot effectively. 

Understanding Freightliner fault codes is essential for diagnosing problems quickly and preventing costly downtime. Whether you operate a fleet or manage your own truck, knowing how to interpret these codes can help you get back on the road faster and protect your business’s bottom line. 

In this guide, we’ll cover:

• What Freightliner fault codes mean

• How to read Freightliner diagnostic trouble codes

• A Freightliner fault code list with explanations

• Common causes of Freightliner fault codes

• How to clear Freightliner error codes

• The best diagnostic tools for Freightliner trucks

Table of Contents

1. What Are Freightliner Fault Codes?

1. How to Read Freightliner Fault Codes

2. How to Locate Freightliner Fault Codes

2. The Complete Freightliner Fault Code List

3. How to Clear Freightliner Fault Codes

4. The Best Way to Diagnose Freightliner Fault Codes

5. FAQ

What Are Freightliner Fault Codes?

Freightliner trucks use onboard electronic control units (ECUs) to monitor vehicle performance and detect system faults. When a problem occurs, the ECU generates a Diagnostic Trouble Code (DTC), also known as a fault code, trouble code, or error code, that identifies the affected system.

How to Read Freightliner Fault Codes

Most Freightliner trucks follow the SAE J1939 standard, which uses SPN (Suspect Parameter Number) and FMI (Failure Mode Indicator) codes.

Example Freightliner Code: SPN 110 FMI 3

• SPN 110 – Coolant temperature sensor

• FMI 3 – Voltage above normal or shorted high

This code tells technicians that the coolant temperature sensor circuit is experiencing an electrical issue.

How to Locate Freightliner Fault Codes

There are multiple methods available for accessing Freightliner fault codes. Results may vary depending on the make and model you have.

With a Scanner

Method 1: By far the easiest method of retrieving fault codes is using a diagnostic scanner, such as Jaltest. 

Connect the diagnostic link or scanner to the truck’s diagnostic port. Once connected, you should be able to view and clear any active fault codes from the diagnostic software.

With Jaltest’s troubleshooting guides and OBD capabilities, many techs are able to initiate calibrations, resets, and troubleshoot the issue from the software.

Without a Scanner

Method 2: This is a no scanner method for newer Freightliner models.* 

1. Put the vehicle into park.

2. Turn the ignition key to the “ON” position.

3. Use the steering wheel buttons to navigate to the "Diagnostics” menu, represented by a wrench symbol.

4. Press the appropriate button to confirm your choice.

5. Once in the diagnostics menu, you should be presented with the various modules available, such as engine, transmission.etc. There may be a hazard icon next to some of the modules which indicates that the module has an active fault. 

6. Once you select the module, any active fault codes should be displayed on the dashboard.

Keep in mind that this will only display the fault code. Descriptions of the fault aren’t usually shown and troubleshooting cannot be done within the vehicle’s dashboard.

Method 3: This is a no scanner method for older Freightliner models.*

1. Put the vehicle into park.

2. Find the “mode” and "reset" buttons on the dashboard and use them to scroll through the menu.

3. Find the option labelled “DIAG” or “DIAGNOSTICS”.

4. To enter the diagnostics menu, press and hold down the button again.

5. After this, the number of active faults should be displayed on the dashboard. 

6. Use the button to scroll through active fault codes.

Keep in mind that this will only display the fault code. Descriptions of the fault aren’t usually shown and troubleshooting cannot be done within the vehicle’s dashboard.

The Complete Freightliner Fault Code List & Their Meanings

Diagnostic System Modules (MID Codes)

Code	System	Description
MID 128	Engine Control Module	Primary engine electronic control module
MID 130	Automatic Transmission	Transmission control module
MID 136	Anti-Lock Braking System	ABS braking controller
MID 140	Instrument Panel	Left dashboard display module
MID 142	Instrument Panel	Right dashboard display module #1
MID 172	Diagnostic System	Vehicle diagnostic monitoring system
MID 179	Data Logger	Event data recorder / black box
MID 181	Satellite Communication	Satellite communication controller
MID 190	Air Conditioning	HVAC system control unit
MID 219	Radar / Collision Avoidance	Vehicle radar collision avoidance system
MID 231	Cellular Communication	Cellular network communication system
MID 234	Instrument Panel	Right dashboard display module #2

Parameter Identifier Codes (PID 51–63)

PID Code	Parameter
PID 51	Throttle Pedal Position
PID 52	Intercooler Temperature
PID 53	Synchronizer Clutch Status
PID 54	Synchronizer Brake Status
PID 55	Shift Finger Position
PID 56	Range Switch Status
PID 57	Transmission Actuator Status #2
PID 58	Gear Shift Controller Status
PID 59	Gear Shift Motor Status
PID 60	Shift Rail Position
PID 61	Parking Brake Actuator Status
PID 62	Engine Retarder Status
PID 63	Transmission Actuator Status #1

Parameter Identifier Codes (PID 64–97)

PID Code	Parameter
PID 64	Direction Switch Status
PID 65	Service Brake Switch Status
PID 66	Vehicle Enable Component Status
PID 67	Transmission Shift Request Switch
PID 68	Torque Limiting Factor
PID 69	Two-Speed Axle Switch Status
PID 70	Parking Brake Switch
PID 71	Idle Shutdown Timer Status
PID 72	A/C Blower Bypass Valve Position
PID 73	Auxiliary Water Pump Pressure
PID 74	Maximum Road Speed
PID 75	Steering Axle Oil Temperature
PID 76	Lift Axle Air Pressure
PID 77	Front Drive Axle Oil Temperature
PID 78	Rear Drive Axle Oil Temperature
PID 79	Road Surface Temperature
PID 80	Washer Fluid Level
PID 81	Particle Trap Pressure
PID 82	Air Starter System Pressure
PID 83	Road Speed Limit Status
PID 84	Road Speed
PID 85	Cruise Control Status
PID 86	Cruise Set Speed
PID 87	Cruise High-Set Speed
PID 88	Cruise Low-Set Speed
PID 89	PTO Status
PID 90	PTO Oil Temperature
PID 91	Accelerator Pedal Position (%)
PID 92	Engine Load (%)
PID 93	Output Torque
PID 94	Fuel Injection Pressure
PID 95	Fuel Filter Pressure Difference
PID 96	Fuel Level
PID 97	Water in Fuel Indicator

Engine Sensor Parameters (PID 98–127)

PID Code	Sensor / Parameter
PID 98	Engine Oil Level
PID 99	Oil Filter Pressure Difference
PID 100	Engine Oil Pressure
PID 101	Crankcase Pressure
PID 102	Turbo Boost Pressure
PID 103	Turbocharger Speed
PID 104	Turbo Oil Pressure
PID 105	Intake Manifold Temperature
PID 106	Air Inlet Pressure
PID 107	Air Filter Differential Pressure
PID 108	Barometric Pressure
PID 109	Coolant Pressure
PID 110	Coolant Temperature
PID 111	Coolant Level
PID 112	Coolant Filter Differential Pressure
PID 113	Compressor Governor Droop
PID 114	Battery Current
PID 115	Alternator Current
PID 116	Brake Application Pressure
PID 117	Primary Brake System Pressure
PID 118	Secondary Brake System Pressure
PID 119	Hydraulic Retarder Pressure
PID 120	Retarder Oil Temperature
PID 121	Engine Retarder Status
PID 122	Engine Retarder Percentage
PID 123	Clutch Pressure
PID 124	Transmission Oil Level
PID 125	Transmission Oil Level Indicator
PID 126	Oil Filter Differential Pressure
PID 127	Oil Pressure

Failure Mode Indicator Codes (FMI)

FMI Code	Failure Type
FMI 0	Data Above Normal Range
FMI 1	Data Below Normal Range
FMI 2	Erratic or Intermittent Signal
FMI 3	Voltage Above Normal / Short to Power
FMI 4	Voltage Below Normal / Short to Ground
FMI 5	Open Circuit / Low Current
FMI 6	Current Above Normal
FMI 7	Mechanical System Not Responding
FMI 8	Abnormal Frequency or Pulse
FMI 9	Abnormal Update Rate
FMI 10	Abnormal Rate of Change
FMI 11	Unknown Fault
FMI 12	Component Failure
FMI 13	Calibration Error

How to Clear Freightliner Fault Codes

Once you believe you’ve corrected the issue, it’s time to clear the fault code. Clearing Freightliner fault codes should only be done after the underlying issue is repaired.

We recommend clearing fault codes with a diagnostic scanner, such as Jaltest. Here’s the steps on how to do it.

1. Connect a diagnostic tool to the truck

2. Identify the stored fault codes

3. Repair the root cause

4. Clear the code from the ECU

5. Run the engine to verify the issue is resolved

If you clear the fault code but the fault code later reappears, that usually means the issue was not completely fixed. Additional troubleshooting is needed.

Clearing Freightliner Fault Codes Without a Scanner

To clear Freightliner Fault Codes without a scanner:

• Navigate to the “Diagnostics” menu again using the instructions above. From there, you should have the option to clear fault codes. 

• You may be able to reset the ECU by disconnecting the main chassis batteries for at least 20 minutes. When the ECU resets, the fault code should be gone (assuming it was fixed correctly). 

• If nothing works, don’t worry. The vehicle’s computer will usually clear fault codes on its own after the issue has been resolved.

The Best Way to Diagnose Freightliner Fault Codes

While it’s possible to read basic Freightliner codes from the dashboard, most repairs require a professional diagnostic tool like Jaltest Diagnostics. 

Jaltest CV (Commercial Vehicle) diagnostic software supports over 60+ Freightliner makes and models, allowing technicians to perform dealer-level diagnostics across major systems including:

• Engine management

• Transmission control

• Emissions systems

• Electrical modules

• Instrument clusters

Furthermore, Jaltest is a multi-brand diagnostic tool, which means it works across multiple brands and manufacturers. Jaltest supports 1,000+ other heavy-duty truck manufacturers including Cummins, Mack, Kenworth, Hino, Volvo, Peterbilt, and much more. 

This is especially useful for mixed fleets that operate more than just Freightliner trucks, or trucks equipped with engines and components from other manufacturers. It acts as an all-in-one solution, reducing the need for costly manufacturer-specific diagnostic software licenses. 

You reduce your workflow and budget to one all-encompassing diagnostic tool that does it all. 

The software also includes step-by-step repair guidance, wiring diagrams, and system tests that make troubleshooting significantly faster. 

Schedule a 1-on-1 demo to find out how the software works, and how it can simplify your day-to-day operations.

Frequently Asked Questions About Freightliner Fault Codes

What is the fault code 1 on a Freightliner truck?

Fault code 1 could be referring to Freightliner fault code 1 SID 254, which indicates that there are communication problems in the vehicle’s Electronic Control Module (ECM) or between different control modules on the vehicle network.

This fault code can be caused by: 

• Damaged or loose wiring in the CAN data link

• Corroded or disconnected connectors

• Faulty control modules

• Low system voltage or battery issues

• Problems with the vehicle’s data bus (J1939 or J1708)

To fix the issue, we recommend inspecting the data link wiring, battery voltage, and module connections. If there are no issues there, you may need to replace faulty components. 

Complex electronic vehicle communication problems like this are solved best by OEM-level diagnostic software such as Jaltest. Jaltest can give you more insight into what’s causing the issue without needing to rule out problems with trial and error troubleshooting.

Can I drive with a Freightliner fault code?

Some codes are minor warnings, but others can trigger engine derate or limp mode. Driving with serious fault codes can lead to further damage. If a fault code is triggered, techs should assess whether the code is a permanent code that requires troubleshooting before continuing operations.