Mack Truck Fault Code List – Do You Know This?

Mack trucks use a proprietary diagnostic system called V-MAC (Vehicle Management and Control) to monitor and troubleshoot issues with vehicles. The V-MAC system uses diagnostic trouble codes (DTCs) to identify and communicate any issues that may arise with the truck.

Diagnostic trouble codes are stored in the truck’s onboard computer and can be accessed using a diagnostic tool. When a problem is detected, the V-MAC system will set a fault code and turn on the check engine light on the dashboard. The fault code can be used to identify the specific problem and determine the appropriate course of action to fix it.

How to Get Mack Truck Fault Code Reading

To read and interpret fault codes on a Mack truck, you will need to use a diagnostic tool specifically designed for this purpose. There are several options available, including:

Mack V-MAC IV: This is a diagnostic tool specifically designed for use with Mack trucks. It allows you to read and clear fault codes, perform diagnostic tests, and access detailed troubleshooting information.
JPRO Professional: This is a diagnostic tool that supports a wide range of heavy-duty vehicles, including Mack trucks. It allows you to read and clear fault codes, perform diagnostic tests, and access detailed troubleshooting information.
Nexiq USB Link 2: This is a diagnostic tool that supports a wide range of heavy-duty vehicles, including Mack trucks. It allows you to read and clear fault codes, perform diagnostic tests, and access detailed troubleshooting information.

While these tools can help get a fault code for your Mack truck, they are not designed to resolve the problem.

MID, PID, SID

In general, fault codes consist of a MID and a PID or SID that together identify the specific problem. Below, I’ll explain what these codes mean individually and how they come together.

MID

MID stands for Module Identifier, and it is a part of the DTC used by the V-MAC system of a Mack truck to identify the module or system where a specific problem is located. The MID is combined with a Subsystem Identifier (SID) to identify the specific problem.

Here is a list of some common MIDs used in Mack trucks:

MID 128: Engine
MID 130: Transmission

MID 136: Brakes
MID 140: Vehicle Control and Communication
MID 142: Electronic Control Unit (ECU)

MID 144: Vehicle Information and Communication
MID 146: Instrumentation
MID 150: Cab Climate Control

MID 152: Cab Climate Control
MID 162: Fuel
MID 164: Fuel Pump

MID 166: Fuel Tank
MID 170: Intake Air Heater
MID 172: Exhaust Gas Recirculation (EGR)

MID 174: Exhaust Gas Temperature (EGT)

For example, a fault code of MID 128 SID 4 would indicate a problem with the engine throttle valve 1 circuit in the MID 128 (engine) module. Similarly, a fault code of MID 144 SID 230 would indicate a problem with the engine speed data in the MID 144 (vehicle information and communication) module.

PID

PID stands for Parameter Identifier, and it is a part of the DTC used by the V-MAC system of a Mack truck to identify a specific problem within a particular module or system. The PID is combined with a MID to identify the specific problem.

Here is a list of the most common PID codes that correlate with a MID.

MID 128 PID 27: Engine Speed Data
MID 128 PID 45: Throttle Potentiometer Circuit

MID 128 PID 91: Engine Coolant Temperature Data
MID 128 PID 97: Engine Oil Pressure Data
ID 128 PID 110: Engine Timing Data

MID 128 PID 174: Engine Throttle Valve 2 Circuit
MID 128 PID 190: Throttle Actuator Control Motor Circuit

For example, a fault code of MID 128 PID 27 would indicate a problem with the engine speed data in the MID 128 (engine) module. Similarly, a fault code of MID 144 PID 72 would indicate a problem with the engine speed data in the MID 144 (vehicle information and communication) module.

SID

SID stands for Subsystem Identifier, and it is a part of the DTC used by the V- system of a Mack truck to identify a specific problem within a particular module or system. The SID is combined with a MID to identify the specific problem.

Here are a couple of examples of SID and how it relates to MID:

MID 128 SID 1: Engine Throttle Valve 1 Circuit

MID 128 SID 21: Throttle Actuator Control Motor Circuit

FMI

There is a fourth identifier called FMI (Failure Mode Identifier) to help pinpoint the problem of a Mack truck. The FMI codes are standardized and used across different types of heavy-duty vehicles, including Mack trucks. The specific meaning of an FMI code will depend on the MID and SID it is associated with, as different modules and systems have different functions and components.

Here is a list of some common FMI codes used in Mack trucks:

FMI 0: Data is erratic, intermittent, or incorrect
FMI 1: Data is valid but above normal operational range

FMI 2: Data is valid but below normal operational range
FMI 3: Voltage above normal or shorted to high source
FMI 4: Voltage below normal or shorted to low source

FMI 5: Current above normal or grounded
FMI 6: Current below normal or open circuit
FMI 7: Mechanical system not responding or out of adjustment

FMI 8: Abnormal frequency or pulse width or period
FMI 9: Abnormal update rate
FMI 10: Abnormal rate of change

FMI 11: Root cause unknown

For example, a fault code of MID 128 SID 4 FMI 5 would indicate a problem with the engine throttle valve 1 circuit in the MID 128 (engine) module, with the specific failure mode being Throttle Actuator Control Motor Circuit Failed High.

Mack Truck Fault Codes List

There are many different fault codes that can be stored in the V-MAC system of a Mack truck. It’s not possible to list all of them here as there are hundreds of codes that can be generated by the various systems and components of a Mack truck.

Codes can vary between brands and vehicle models. The best thing you can do to figure out what the problem is to plug your diagnostics tool into your Mack truck, get the fault code, and consult the owner’s manual to see what you can do (if anything) to resolve the problem.

Here are some of the more common fault codes that may arise in a Mack truck:

Fault Code	Description
MID 128 PID 27	Engine Speed Data Valid But Above Normal Operational Range – Most Severe Level
MID 128 PID 45	Throttle Potentiometer Circuit Failed Low
MID 128 PID 46	Throttle Potentiometer Circuit Failed High
MID 128 PID 47	Throttle Potentiometer Circuit Intermittent
MID 128 PID 91	Engine Coolant Temperature Data Valid But Above Normal Operational Range – Most Severe Level
MID 128 PID 97	Engine Oil Pressure Data Valid But Below Normal Operational Range – Most Severe Level
MID 128 PID 98	Engine Oil Pressure Data Valid But Above Normal Operational Range – Most Severe Level
MID 128 PID 110	Engine Timing Data Valid But Above Normal Operational Range – Most Severe Level
MID 128 PID 111	Engine Timing Data Valid But Below Normal Operational Range – Most Severe Level
MID 128 PID 174	Engine Throttle Valve 2 Circuit Failed Low
MID 128 PID 175	Engine Throttle Valve 2 Circuit Failed High
MID 128 PID 190	Throttle Actuator Control Motor Circuit Failed Low
MID 128 PID 191	Throttle Act