When you’re faced with a malfunctioning Mack truck, understanding the language of OBD/OBD2 codes is essential to getting back on the road quickly. You’ve likely encountered those cryptic five-digit combinations on your dashboard or scan tool, but what do they really mean? The first digit holds a secret: it reveals whether the issue is specific to Mack trucks or a generic problem.
But that’s just the beginning—deciphering P, B, C, or U codes can lead to the root of common problems like faulty fuel systems or transmission issues. What’s hiding behind those codes, and how can you crack the code to get your truck running smoothly again?
Quick Navigation
Understanding Mack Fault Codes
When diagnosing issues with your Mack truck, understanding Mack Fault Codes is crucial to identifying and resolving problems efficiently.
To interpret these codes accurately, you need to know the DTC format, which consists of two parts: system/component identification and problem identification.
Mack Diagnostic Trouble Code guides provide detailed information on fault codes and their meanings, helping you diagnose problems and determine necessary repairs.
You can use a scan tool or code reader to retrieve fault codes and monitor vehicle systems, such as the Engine Control Module (ECM), Aftertreatment Control Module (ACM), and Transmission Control Module (TCM), which control and idle functions.
Common Mack Truck Problems
Mack trucks, like any complex machinery, are prone to various problems that can hinder their performance and safety on the road.
As a truck owner, you’re likely to encounter some issues that can trigger fault codes and affect your vehicle’s overall reliability.
- Improper maintenance can lead to engine damage and other issues, such as using the wrong type of oil or not changing it often enough.
- Tire problems, including uneven wear and blowouts, can occur due to overloading, rough roads, or poor maintenance.
- Transmission problems can arise from towing too much weight, improper shifting, or using the wrong transmission fluid.
These common problems can lead to fault codes and other safety issues if not addressed promptly.
Deciphering OBD-II Codes
Deciphering OBD-II codes is a crucial step in identifying and addressing issues with your Mack truck.
These five-digit codes provide specific information on the troubled vehicle system or circuit, categorized into powertrain, network and integration, body, and chassis subsets.
The first digit indicates if the code is manufacturer-specific (1) or generic (0), helping you diagnose issues.
The largest category is P codes, which deal with the powertrain system. This category includes fuel and air metering and transmission system problems.
To aid in diagnosis and repair, search OBD-II codes by P, B, C, or U codes and check for safety recalls using your vehicle’s VIN or license plate number.
This will help you identify the Truck Fault and corresponding diagnostic trouble codes, enabling you to take corrective action.
Most Common Mack OBD-II Trouble Codes
Engine Related Codes
| Code | Description |
|---|---|
| MID 128 PSID 1 FMI 1 | Engine Oil Pressure Sensor Circuit Fault |
| MID 128 PPID 35 FMI 0 | Low Engine Coolant Level |
| MID 128 SID 2 FMI 2 | Abnormal Engine Speed Rate Change |
| MID 128 SID 18 FMI 3 | Fuel Injection Pump Not Responding |
| P0420 | Catalyst System Efficiency Below Threshold |
| P02FA | Diesel Intake Air Flow Position Sensor Min/Max |
| P24DA | Particulate Matter Sensor Exhaust Sample Error Bank 1 |
| P009E | Fuel Pressure Relief Control Performance/Stuck Off |
| P0471 | Engine Exhaust Back Pressure Circuit Range/Performance |
| P1031 | Particulate Matter Sensor Clogged Tip |
Emissions Control Codes
| Code | Component/Function | FMI Codes |
|---|---|---|
| MID 128 PID 81 | Particulate Trap Differential Pressure | 0, 2, 3, 5, 12 |
| MID 128 PID 94 | Fuel Pressure | 1, 3, 5, 7 |
| MID 128 PID 102 | Boost Pressure | 0, 2, 3, 5, 11 |
| MID 128 PID 103 | Turbo Speed | 0, 1, 9 |
| MID 128 PID 105 | Boost Temperature | 2, 4, 5, 10 |
Vehicle Control Codes
| Code | Component/Function | FMI Codes |
|---|---|---|
| MID 144 PID 72 | Output Supply #1 | 3, 4 |
| MID 144 PID 73 | Output Supply #2 | 3, 4 |
| MID 144 PID 84 | Road Speed | 2 |
| MID 144 PID 91 | Accelerator Pedal Position | 3, 4, 5, 6, 14 |
| MID 144 PPID 61 | Engine Retarder Switch | 7 |
Aftertreatment Codes
| Code | Component/Function | FMI Codes |
|---|---|---|
| MID 128 PPID 328 | After Treatment Injection Shut-off Valve | 3, 4, 5, 7, 14 |
| MID 128 PPID 329 | After Treatment Fuel Injector | 3, 4, 5, 7, 14 |
| MID 128 PPID 387 | Exhaust Gas Temperature Sensor #2 | 2, 4, 5, 10 |
| MID 128 PPID 436 | Exhaust Gas Temperature Sensor #3 | 0, 2, 4, 5, 10 |
Note: FMI (Failure Mode Identifier) codes indicate the type of failure detected for each component. The numbers represent different types of failures such as:
- 0: Data valid but above normal
- 2: Data erratic
- 3: Voltage high
- 4: Voltage low
- 5: Current low
- 7: Mechanical system not responding
- 10: Abnormal rate of change
- 14: Special instructions
