Diagnosing Fault Code [Mid 128 Pid 131 Fmi 4]: A Comprehensive Guide

MID 128 indicates a Cruise Control or Automatic Transmission Control module, and FMI 4 implies a Voltage Above Normal or Shorted High Condition within the module.

Mid 128 Pid 131 Fmi 4

Mid 128 Pid 131 Fmi 4 is a code found on certain on-board diagnostic systems. It typically indicates an issue with the fuel delivery system, such as low pressure at the regulator or injector side of the fuel line. The code can also mean that the fuel pump has not turned on, which could also be caused by a failed relay or loose connection. If this code is present, it is recommended to have a professional diagnose and repair the issue as soon as possible to ensure optimal performance and safety.

Fault Code – Mid 128 Pid 131 Fmi 4

Mid 128 Pid 131 Fmi 4 is an engine fault code associated with the electronic control module (ECM) of diesel engines. It is a diagnostic trouble code that indicates a malfunction in the ECM or its associated components. The symptoms of this fault can vary greatly depending on the cause, but generally include reduced power output, rough idling, stalling, and/or poor fuel economy.


The most common symptom of Mid 128 Pid 131 Fmi 4 is reduced engine power output. This can manifest itself as sluggish acceleration or engine hesitation when accelerating. Other symptoms include rough idling, stalling when the engine is cold, and poor fuel economy.


To diagnose Mid 128 Pid 131 Fmi 4, a diagnostic scanner must be used to connect to the ECM and read any fault codes stored there. If this code appears, it indicates that there is an issue with either the ECM itself or one of its associated components that must be addressed in order to restore normal engine operation.

Common Causes

There are two primary causes for this fault code mechanical issues and electrical system malfunction. Mechanical issues can include faulty sensors or other internal components not functioning correctly due to age or wear-and-tear. Electrical system malfunctions may be caused by loose wiring connections, damaged wiring harnesses, faulty relays or fuses, or defective ECM components such as CPUs or memory chips.

Possible Fixes

To fix Mid 128 Pid 131 Fmi 4, it is necessary to verify and troubleshoot all ECM connections first before attempting any repairs. It may also be necessary to reprogram the ECM if it has become corrupted due to an electrical issue such as power surge or voltage dropouts. If any parts are found to be defective during diagnosis, they should be repaired or replaced as soon as possible in order to restore normal engine operation.

Related Engine Codes

In addition to Mid 128 Pid 131 Fmi 4, there are several other related diagnostic trouble codes that may appear in conjunction with this one depending on the cause of the issue. These codes can range from general codes such as misfires and fuel injection system faults to more specific codes related to individual components such as injectors and fuel pumps.

References and Tools

When diagnosing and repairing Mid 128 Pid 131 Fmi 4 faults it is important to have access to technical manuals for reference purposes as well as an OBD scanner for reading diagnostic trouble codes stored within the ECMs memory modules. Having both these tools available will ensure that you are able to accurately identify any issues quickly and efficiently so that repairs can be made quickly and effectively restoring normal engine operation once again.

Overview of the Fault Code

Mid 128 Pid 131 Fmi 4 is a diagnostic trouble code (DTC) that is related to the engine. This code means that the ECM (Engine Control Module) has detected an issue with the fuel pressure sensor. The ECM monitors the pressure of the fuel system, and when it detects a problem with the fuel pressure, it will set this code.

Common Causes of this Fault Code

The most common causes for this fault code are: a damaged or faulty fuel pressure sensor, an insufficient fuel supply from the fuel pump, and clogged injectors or an air leak in the intake manifold. It can also be caused by a faulty wiring harness or a faulty ECM.

Symptoms of this Fault Code

The symptoms of this fault code can vary from engine to engine, but common symptoms include: engine misfires, reduced engine power, increased fuel consumption, and poor acceleration. The Check Engine Light will also be illuminated when this fault code is present.

Diagnosing and Repairing This Fault Code

To diagnose and repair this fault code, a technician will first need to check for any existing trouble codes using an OBD-II scanner. Once any existing codes have been diagnosed and repaired, they will then need to conduct a visual inspection of all related components such as the wiring harness, fuel pressure sensor, injectors and intake manifold for any signs of damage or corrosion. If any damage is found they will need to be replaced before continuing with the diagnosis.

Next they will need to use a pressure gauge to check the fuel system pressure to ensure that it is within specification. If it is not within specification then they will need to check for any clogs in the system or inspect for any air leaks that may be causing an insufficient supply of fuel to reach the injectors.

Finally if all other components are found to be working correctly then they may need to replace or reprogramme the ECM depending on their findings during their diagnostic process. Once all repairs have been completed then their OBD-II scanner should be used again to clear all stored trouble codes from memory before testing out their repairs on test drive.

FAQ & Answers

Q: What is the fault code Mid 128 Pid 131 Fmi 4?
A: The fault code Mid 128 Pid 131 Fmi 4 indicates an issue with the electrical system of the engine.

Q: What are the symptoms of this fault code?
A: The most common symptom associated with this fault code is decreased engine performance and power. Other issues may also arise, such as stalling or misfiring.

Q: What are some common causes of this fault code?
A: Common causes of this fault code include mechanical problems, electrical system malfunctions, and ECM reprogramming errors.

Q: What steps can be taken to repair this issue?
A: To repair this issue, it is important to verify and troubleshoot all ECM connections, as well as repair and reprogram the ECM if necessary. Additionally, other related engine codes should be checked for further diagnosis.

Q: Are there any references or tools that can help with troubleshooting?
A: Yes, technical manuals and OBD scanners can be very useful in troubleshooting these types of problems.

Mid 128 Pid 131 Fmi 4 refers to a fault code for a vehicles engine control unit. The code indicates that there is an issue with the vehicles fuel pressure regulator, which can be caused by a faulty fuel pump, fuel filter, or other related components. In order to properly diagnose and repair the issue, a qualified mechanic should be consulted.

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