The diagnostic trouble code (DTC) Mid 140 Pid 77 Fmi 5 is not mentioned in the original text. This article will address the issues described in the original text, focusing on potential causes and troubleshooting steps related to similar symptoms often associated with engine derate and shutdown in Mack trucks. While the specific code mentioned in the title is not directly addressed in the source material, the troubleshooting process outlined below can be applied to a wide range of engine performance issues, including those potentially indicated by MID 140 PID 77 FMI 5.
A 2009 Mack CXU613 Pinnacle with an MP7 engine is experiencing intermittent shutdown and derate issues. The truck initially presented with inactive diagnostic trouble codes (DTCs): MID 128 PID 411 FMI 5 (Gas Differential Pressure Sensor) and MID 128 PID 437 FMI 5 (Aftertreatment Injector Fuel Pressure Sensor). Voltage checks at the disconnected sensors revealed a ground, a 4.99-volt reading, and a signal voltage between 4.55 and 4.75 volts.
The primary symptom is an inability to rev the engine past 1200 RPM, often accompanied by engine shutdown or derate while driving. Disabling the cruise control temporarily allows the engine to reach 2200 RPM. Replacing the cruise control switch provided temporary relief, but the problem resurfaced, now accompanied by an illuminated ATC (Aftertreatment Control) light on the dashboard and power reduction. Restarting the truck after a 20-second key-off period temporarily restores normal operation for approximately 50 miles before the issue reoccurs. Soot levels consistently remain between 50-75%, even after forced regenerations.
Potential Causes and Troubleshooting Steps:
Several potential issues could be contributing to the described symptoms. Let’s explore some possibilities and recommended troubleshooting steps:
1. Wiring and Connectors: Given the initial sensor codes and the unusual cruise control interaction, thoroughly inspect the wiring harnesses and connectors associated with the engine control module (ECM), cruise control system, and aftertreatment system. Look for damaged wires, loose connections, corrosion, or chafing. Pay close attention to areas where harnesses might rub against the chassis or other components. A wiring issue could be causing intermittent signal disruptions.
2. Sensor Issues: Although the initial sensor codes became inactive, the sensors themselves could still be faulty. Intermittent sensor failures can be challenging to diagnose. Consider replacing the gas differential pressure sensor and the aftertreatment injector fuel pressure sensor. Use a diagnostic tool to monitor live sensor data while driving to identify any unusual readings or fluctuations.
3. Cruise Control System Malfunction: The temporary resolution achieved by disabling or replacing the cruise control switch suggests a possible issue within the cruise control system itself. While a faulty switch is possible, the problem could also lie in the cruise control module or its associated wiring. Further investigation of the cruise control system’s electrical components and connections is warranted.
4. ECM Issues: Reprogramming and updating the ECM did not resolve the problem, but an intermittent internal fault within the ECM cannot be ruled out. If all other potential causes have been eliminated, consider replacing the ECM with a known-good unit.
5. Aftertreatment System Problems: The persistent high soot levels and the illumination of the ATC light suggest a potential problem within the aftertreatment system. This could include issues with the diesel particulate filter (DPF), diesel oxidation catalyst (DOC), or the selective catalytic reduction (SCR) system. Thoroughly inspect the aftertreatment system for any signs of damage, blockage, or malfunction.
Conclusion:
Diagnosing intermittent engine shutdowns and derate issues can be complex. A systematic approach involving thorough inspection, testing, and elimination of potential causes is crucial. While the provided information doesn’t directly correlate to MID 140 PID 77 FMI 5, the outlined troubleshooting steps provide a solid foundation for addressing similar engine performance problems in Mack trucks. Utilizing a diagnostic tool to monitor live data, perform active tests, and retrieve fault codes will greatly aid in pinpointing the root cause of the problem. Consult the official Mack service information for specific diagnostic procedures and wiring diagrams related to MID 140 PID 77 FMI 5, if applicable, and the other mentioned DTCs.
