When the PCM fails, it can cause a variety of issues that can affect your engine’s reliability and efficiency, and it can often be tricky to tell which ones point to the PCM specifically.
You do need to keep in mind that working on a PCM requires proper tools, extensive knowledge, and lots of experience, so only perform these if you trust your skills and don’t overextend yourself as that can do you more harm than good.
Whether you’re experiencing engine stalling, rough idling, or other issues, you will first need to diagnose the PCM (OBD-II fault codes, multimeter, circuit inspection, sensor inspections) and then proceed toward fixing the PCM or just replacing it.
If you are lucky, you will be able to dodge the brunt of the costs associated with a new PCM replacement ($1,000 to $1,500) via a simple PCM software update, wiring harness replacement, internal circuit replacement, or sensor/actuator replacement.
In this article, we will explore nine common symptoms of PCM failure on 7.3 Powerstroke engines and provide tips on how to fix them.
Whatever you do, it’s not a good idea to drive the car if you are experiencing any of these symptoms as that can cause more damage.
By understanding the symptoms and fixes for PCM failure, you can keep your engine running smoothly and avoid costly repairs down the line.
Symptoms of a Faulty PCM on a 7.3 Powerstroke
- Ignition Troubles/ Starting Problems
- Lights and Error Codes on the Dashboards
- Engine Stalls/Bad Engine Performance
- Increased Emissions
- Bad/Poor Gas Mileage
- Voltage Overload
- Random Shifting/Shifting Problem
- Intermittent Running Problem
- Gauge Cluster Not Functioning Right
Ignition Troubles/ Starting Problems
If your truck fails to start, stalls, or is running roughly, there is a great deal of chance that something is wrong with your PCM.
As the PCM controls various vital engine metrics such as engine ignition, it could lead to the PCM sending the wrong signals to your spark plugs and thus mistime them and cause the engine to run roughly, stall, or not want to start.
Moreover, the PCM controls the engine’s air and fuel mixture system, which means that it decides when and how much fuel ought to enter the chamber for consistent combustion.
If any of these are off, even by a little bit, they could lead to some, or all of the issues mentioned.
Lights and Error Codes on the Dashboard
The first sign that something is wrong with the engine or some of its essential systems is the dreaded “Check Engine Light”.
The problem here is that a CEL can mean a bunch of different things so it’s not always going to be a PCM-related problem.
Therefore, you should look for many other symptoms listed in this article while also trying to scan the car for specific fault codes.
If the PCM is indeed failing, you are likely going to encounter codes such as the U0100 code, the P0606 code, or even the P0603.
Engine Stalls/Bad Engine Performance
Engine stalling, bad emissions, low pulling power, and inconsistent performance are usually related to problems in the ignition, fueling, timing, and air engine metric systems, all of which are controlled by the PCM.
However, it is always a good idea to check some of the car’s mechanical components first just to narrow down the issue.
If your fuel pump, ignition coils, spark plugs, and air filters are okay, you should focus your attention on the PCM as these are often 7.3 Powerstroke PCM failure symptoms.
Increased Emissions
The PCM is responsible for monitoring and controlling various engine sensors and actuators that are used to manage engine emissions.
The PCM monitors the oxygen sensor to determine the oxygen content in the exhaust gases and adjusts the fuel injection timing and air/fuel mixture accordingly to maintain optimal emissions levels.
In addition, the PCM can also monitor other emissions-related systems, such as the catalytic converter and evaporative emissions system, to ensure that they are operating correctly and to detect any issues that may arise.
So, if you fail your emissions testing, you should immediately focus on your PCM as that is usually what causes it.
Bad/Poor Gas Mileage
The PCM is responsible for controlling the fuel and ignition systems of your engine, and if it is not functioning correctly, it can cause a range of issues that could result in poor gas mileage.
As such, a failing PCM may not be able to accurately adjust the air/fuel mixture or ignition timing, which can lead to inefficient combustion and decreased fuel efficiency.
Even though there are many different reasons why your car could suffer from bad/poor gas mileage, (dirty air filters, fuel injector problems, worn plugs, O2 sensor issues), you should indeed inspect the PCM.
Voltage Overload
Your car has many safeguards (electrical fuses, electrical grounding) which serve to protect various vulnerable systems such as the PCM from voltage overload. However, these aren’t always able to protect it.
The PCM relies on a stable supply of voltage and current to function correctly, and if it is subjected to voltage overload or electrical spikes, it can cause damage to the internal components of the PCM and potentially cause it to fail.
If the voltage exceeds the maximum threshold the PCM can handle, it is going to fail, it’s only a question of how serious the damage is going to be.
Random Shifting/ Shifting Problems
All modern-day cars that use automatic transmissions need the PCM to communicate the right data about when to shift and how to shift, which means that a faulty PCM is going to result in random shifting/ shifting problems.
Moreover, the PCM is also tasked with controlling the air-to-fuel mixture, which can also cause random shifts or the car not wanting to shift at all.
This is indeed a really serious issue and most people are going to look at the transmission first.
So, if your transmission seems to be okay and if there is nothing wrong with its essential systems, you should inspect the PCM, especially if you come across multiple Ford 7.3 PCM symptoms listed in this article.
Intermittent Running Problem
The PCM is responsible for controlling the engine’s fuel injection, ignition timing, and other critical systems, and if it is not functioning properly, it can cause the engine to run erratically or intermittently.
If the engine starts and runs normally for a period of time before suddenly stalling or running poorly, it can be due to various engine problems such as failing internal circuits, loose connections, or faulty input sensors.
However, if this symptom is followed by engine stalling, rough idling, the CEL, and some other symptoms listed here, your PCM is likely the culprit.
The idea here is to try to look for as many of these symptoms at the same time, as the more symptoms you encounter, the bigger the chances your PCM is failing.
Gauge Cluster Not Functioning Right
Even though this is not usually one of Ford 7.3 PCM problems, one Powerstroke owner said that installing a block heater caused the gauge cluster to fail and the problem was eventually traced to a faulty PCM.
Issues such as these typically stem from overloading the battery or the rest of the electrical system, which can cause a spike in voltage that could endanger the PCM as mentioned in the “Voltage Overload” paragraph above.
So, before you do anything, go ahead and inspect the battery as that can easily lead you to a faulty PCM or some of the connectors going bad.
What to Do When You Detect a Bad 7.3 Powerstroke PCM
The first step toward remedying a bad 7.3 Powerstroke PCM is to troubleshoot the entire system and make sure that the PCM is actually malfunctioning.
This means that you should first diagnose the problem and then move to solve it.
Be sure to gather these tools before you start your diagnosis process:
- OBD-II Scanner
- Multimeter
- Screwdriver
- Flashlight
How to Diagnose a Faulty 7.3 Powerstroke PCM?
Voltage Measurements
The first thing you need to do is test out the battery voltage to see if the battery is providing enough juice to the PCM.
If all is well, the battery should read around 13.7 volts consistently with the engine idling or 12.6 volts while the engine is off.
Any lower than this means that your battery either needs charging or a complete replacement if the measurements are really low.
Circuit Inspection
Now it’s time to tackle PCM connections directly, which means that you need to ensure that none of the wires are corroded, rusty, or not connected properly.
Go ahead and disconnect the PCM, and test out all the wires via a multimeter to see if they are running any power.
If all of the wires are fine, you should also test out the circuit grounding to see if it is able to protect the system.
Scan the PCM via an OBD Scanner
Get ahold of an OBD scanner, connect it to the car, and start scanning the PCM for any diagnostic fault codes.
If the PCM is malfunctioning, chances are that you will encounter some of these codes (U0100, P0606, P0603…).
If there are no codes to speak of, you are either using a low-quality OBD scanner or there is actually nothing wrong with the PCM.
Check the Sensors
If the scanning process did prompt up a few codes, it’s now time to get ahold of a fault code manual and look for the sensors and circuits that need further diagnosing.
Once you find them, you will have to replace the damaged parts, reset the codes, and try to re-scan the system to see if all of the codes have been cleared.
If you did everything there is to do and the codes are still present, it is usually suggested that you should replace the PCM completely.
How to Fix a Faulty 7.3 Powerstroke PCM
Fixing a 7.3 Powerstroke PCM failure is a complex and often time-consuming process that should be left to professionals. The PCM is rather expensive and often difficult to fix without replacement.
Therefore, we are going to help you fix it, but if you are not familiar with all of these processes thoroughly, you should skip it and take your car to an experienced mechanic.
Repair the Internal Circuits
If the issues with the PCM are caused by a failure in one of the internal circuits, it may be possible to repair the circuit instead of replacing the entire PCM.
Replacing these circuits should only be done if your multimeter readings show that some of your wires are the reason why the PCM failed.
This means that if there are other underlying issues, and you don’t catch them, there is a good deal of chance that even your new internal circuits are going to fail.
Replace Sensors and Actuators
If the issue is caused by a faulty sensor or actuator that is sending incorrect signals to the PCM, the sensor or actuator will need to be replaced.
This is one of the easier and not too complicated methods of solving a faulty PCM problem, and the most common symptoms that cause it are:
- Camshaft Position Sensor
- Crankshaft Position Sensor
- Manifold Absolute Pressure (MAP) Sensor
- Exhaust Gas Recirculation (EGR) Sensor
- Fuel Injection Control Module (FICM) Sensor
Perform Software Updates
In some cases, software updates may be available that can fix issues with the PCM if everything else seems to be okay.
Granted, this is not often the case, but it could save you a bunch of money because you will not have to buy a new PCM and install it.
Replace the PCM
If the PCM is completely non-functional or cannot be repaired, it will need to be replaced, but it is always a good idea to try all the other methods listed above first.
The new PCM will need to be programmed with the correct software and settings to match your specific vehicle, which is also something you should leave to a qualified professional exactly because the PCM controls the very essential powertrain metrics.
You can save some money if you source your PCM yourself and only pay for the labor costs.
FAQs
