Ford PCM Reset: Here's When and How You Should Reset the PCM

A PCM reset can save you the hassle of time and, more significantly, money that you could have used to replace unnecessary car parts. This article will cover what a PCM reset is and when and how you should reset the PCM in your Ford. Let's start with a brief introduction to a PCM and how it functions.

PCM problems highlights

• Module's importance:Extremely high
• Prone to failure:Yes
• Reasons for failure:Water, damage, ECM problems, TCM problems
• Ways to reset:Disconnecting, scanner tool diagnostics
• Sphere of control:Powertrain (engine, transmission, AWD systems)
• Symptoms of failing:Powertrain anomalies, powertrain codes
• Price to repair:$180 - $300
• Price to replace:$750 - $1,650

What is PCM?

The powertrain control module (PCM) is an onboard computer in a vehicle that has a similar function to the brain or a computer's processor. This is because it controls many functions and dictates how well the car performs. Depending on the car, It can also be referred to as the electronic control unit (ECU) or engine control module (ECM). 

How Does the PCM Function?

The powertrain control module receives signals from sensors measuring different parameters throughout the vehicle. For instance, the crankshaft position sensor in the internal combustion engine measures the rotational speed (RPM) and determines the crankshaft's position.

The PCM then receives the information from the crankshaft sensor. After the PCM receives the signals from different sensors, it processes the information and acts accordingly by making the required adjustments in split seconds. This enhances drivability and enables your car to run at optimum performance and efficiency.

The PCM's important functions include controlling the ignition timing, coolant temperature, air-fuel mixture ratio, automatic transmission shifts, oil level engine emissions, and idle speed. It also harmonizes modules such as the transmission and body control modules.

The PCM works through three components: the memory, processor, and input and output circuits. Now that you have an idea of how it works, let's look at when you should reset it.

When Should You Reset Your Ford's PCM?

Various reasons may compel you to reset your Ford's powertrain control module. These are:

For one, if your Ford truck or car is experiencing an issue related to the PCM, one of the recommended fixes includes resetting the powertrain control module. Some of those issues are:

• Shifting problems such as hard, delayed, or irregular shifting.
• RPM fluctuations.
• Low and rough idle.
• Shuddering and excessive jerkiness when accelerating from a stop.
• A loss in acceleration.
• Engine stalling and the car stuttering when starting or refusing to start completely.
• The check engine light comes on.
• A decline in fuel economy.

Resetting your ECU can also come in handy before replacing car parts. This is because there could be a glitch in the PCM system, which can cause it to store a wrong DTC (diagnostic trouble code). The incorrect code or an electrical issue can mislead you to make a wrong replacement costing you time and money.

Resetting the ECU allows you to determine if the replacement is necessary. You'll know that the replacement needs to happen if after resetting the DTC or the warning light - such as the check engine light - reappears in the dashboard.

After installation of modifications in your car, it's important to reset your Ford's PCM. It also applies to replacing a faulty car part. Resetting the car computer helps the PCM learn the aftermarket modifications or replaced parts and their codes and afterward store their data.

Another instance you need to reset your Ford's PCM is when you have replaced the car's battery. This is because the ECU needs to get familiar with the new battery specifications such as the Rc rating and Ah rating.

Processing the charging specs allows the system to set the correct charging algorithm. For instance, if the previous battery was old and needed overcharging, failure to perform a reset can cause the charging system to continue overcharging the new battery. Overcharging will then shorten the new battery's life.

If the software of the powertrain control module is corrupted, then a reset is the best option. This will help the PCM return to normal. 

Now that you are familiar with some of the instances in which you should reset your PCM let's look at ways to reset your PCM.

How to Reset Your Ford's PCM

There are three ways in which you can reset your Ford's PCM. One is when the battery is on and involves the fuse box. The second is by using a diagnostic tool like an OBD II. The third happens when the battery is off. Let's look at the three in detail. 

1) PCM Reset through the Fuse Box

This is the easiest method and takes only a small amount of time. It also comes in handy if you don't want to deal directly with the battery. 

Steps to take for the reset include:

• Open the hood of your Ford.
• Locate the fuse box in the engine compartment. It often has a casing that displays the amperage and fuses inside.
• Place your finger on the notch of the fuse box lid and carefully remove the lid.
• Find the fuses named "ECU" and "BACKUP" and carefully pull them out. Ensure the ignition key is off before removing the fuses.
• Wait for at least ten minutes before you return them to the exact position where you removed each one.
• Return the lid to its original position.
• Drive for a few miles for the error codes or warning lights to clear if they are still present.

2) Using a Diagnostic Tool

You can use a diagnostic tool like an OBD II to scan, read, and also erase the codes stored in the powertrain control module. The scan tool helps diagnose what's wrong with your vehicle, especially when warning lights, such as the check engine light, comes on in the instrument panel. After fixing the issue, the OBD II helps to clear the existing fault codes and warning lights. 

Steps to reset a warning light and clear error codes:

• Connect the OBD II cable to the OBD port located under the steering column.
• Insert the ignition key and cycle it to the on position without starting the vehicle. The lights on the dashboard should come on.
• Switch off the car accessories like the AC and radio.
• Press the erase button on the scanner tool to clear any diagnostic trouble codes.
• Wait until the "no codes" message comes on in the scanner, then switch off the ignition key.
• Take your car for a test drive to clear any warning light if it still appears on the dashboard. If the warning light doesn't clear after a couple of miles, then the issue is still not fixed, and you need to consult your mechanic.

3) PCM Reset through the Battery

Resetting the PCM through the battery reverts the PCM to factory reset mode. This means the reset erases all the learned memory.

Steps to resetting the PCM through the battery:

• Open the hood of your Ford.
• Use a deep socket to disconnect the negative cable from the battery's negative terminal.
• Place the cable on an insulator like cardboard or a rag to prevent it from touching the battery or a metallic object.
• Get a jumper cable and clip one end to the disconnected negative cable and the other to the connected positive cable and leave it for about 10-15 minutes. Connecting the jumper cable helps to drain the remaining charge from the ECU capacitor.
• Unplug the jumper cable from the battery cables and reconnect the negative cable on its terminal. Use the deep socket to ensure the cable is tight.
• Insert the key in the ignition, turn it to an on position without starting the car, and leave it in that position for 10 seconds. Turn it off and repeat the step.
• Crank the car, let it warm up, and idle for five minutes. This helps the PCM that has undergone a reset relearn the idling values. Ensure accessories like AC are switched off.
• Take the vehicle for a test drive shifting through the gears. This helps the PCM to relearn the shift points and fuel trims. At this point, all the error codes and warning lights should have cleared. If not, the issue still needs fixing.

Tips to Consider During a PCM Reset

A PCM reset doesn't always turn out well and may result in complications. Before you conduct the reset, you should weigh your options to determine if it's the best option. Below are the tips to consider.

• Before resetting your PCM, it's important to have a jump starter as an alternative power source in case you face any battery issues.
• The battery protects the car's electrical components from transients and AC spikes; removing it can damage the electrical components.
• Erasing the error codes stored in the PCM makes it more difficult, time-consuming, and costly to zero in on a correct diagnosis if there's an issue with your car. This is because the diagnostic tool which reads and interprets the error code won't find any code that leaves a clue to the issue.
• Resetting the ECU through the battery can also damage the ignition system due to voltage spikes causing your Ford to refuse to start.
• You can better solve issues related to idling by cleaning the engine's carbon buildup and the throttle body. This means you don't have to reset the PCM.
• Some features and accessories, such as the heating system, window defoggers, AC, and headlights, can become faulty after a reset of the PCM.
• The charging system may be affected after a PCM reset. This is because modern computerized cars have an electronic battery sensor on the negative cable. Tampering with the sensor may cause the charging system to malfunction.
• Resetting the PCM has the risk of aggravating the issue that led you to reset it in the first place. There's also the risk of damage to other car parts for DIYers who are not skilled or experienced in resetting the PCM.

Bottom Line

There you go - when and how to reset your Ford's PCM. Resetting the power train control module has both its pros and cons. Before you perform the reset, it's better to weigh your options and make an informed decision. You should also consult a professional mechanic when in doubt.