What Does PCM Fuse Mean?

As a car owner, I’m sure a malfunctioning powertrain control module (PCM) relay isn’t what you wish to experience. Perhaps, you’re not familiar with the function of this vital car part? With the PCM, you won’t need the tune-up service of your technician. Thanks to the PCM which centrally regulates and monitors your car’s transmission control module (TCM) and the engine control module (ECM).   

What is a PCM?

The powertrain control module is summarily your vehicle’s brain. It is responsible for running the car’s transmission, engine, and other critical systems in the car. It works on the information it receives from the various sensors installed in your car and transmits the same to all parts.

Depending on the make of your car, the TCM and ECM can be combined to mean the PCM. Some automakers make the PCM a standalone computer.

Between these systems, there is a wide range of control and vehicle management functions. The PCM is central to managing the fuel injection parameters to controlling how your transmission shifts gears.

It also determines when and how to activate and deactivate your vehicle’s check engine light. A problem with the powertrain control module is a problem for your car.

What Does the PCM Fuse Mean?

From your understanding of what the PCM is and does, you can tell what the PCM fuse means. Regardless of what name, size, or type it’s, a car fuse is a component that protects the electrical wiring in your vehicle. Auto fuses guard against short-circuiting and overcurrent as they disconnect the auto circuits once they detect a hazardous short-circuit or overcurrent. 

These mostly blade-type, plastic-body, two-pronged units come in almost the same design. They’re suited to different applications and are mounted in fuse holders, fuse clips, and fuse blocks.

The PCM fuse is a two-terminal electrical module in your car that conducts amperes and currents up to maximum level. The PCM fuse is responsible for protecting the powertrain control module from receiving too short or too high currents. This device allows current to flow into the PCM until it reaches the required unit the PCM needs to function optimally.

Let me burst your bubble. There are several fuses that control the amount of current that goes into your vehicle’s PCM. The PCM power is managed by many fuses.   

Once an excessive current passes through the PCM, the insulation in the fuse will melt to prevent damage to your vehicle’s brain. Like other automotive fuses, once the PCM fuse blows, no more current will flows into the PCM. As a result, the fuse will disconnect the circuit, cutting off the PCM from getting the predesigned current limit.

What Happens if the PCM Fuse Blows?

Apart from allowing current flow into the PCM, the PCM fuse provides protection to the PCM in case of an electrical surge. Hence, it helps prevent the central system from overcurrent or undercurrent.

However, when the device opens up, melts and blows, the PCM loses power, preventing control of the ignition process. The result is that it disconnects all wiring that enables electrical distribution to the various components of the PCM.

As a result, the spark to fire the engine into action; the throttle will also shut and the fuel supply will cease. In fact, the entire operation and activity of the engine will cease, deactivating the car from moving.

Why Does PCM Fuse Keep Blowing?

Nothing can be more frustrating than experiencing a blown fuse each time you replace it. There are a couple of factors that can be responsible. The prime suspect is a bad PCM. A short in the wiring harness is also something to look at. Short circuits, overloading, or faulty appliances are also culprits.

But primarily, if the PCM itself is damaged or has gone bad, the fuse cannot be functional. One of the symptoms of a PCM system failure is that your car won’t start. It may start but roughly. A spoilt wiring harness is one major reason the PCM will fail to work, leading to the car’s not starting.

Whether it is the wire harness or a defective PCM, you should attend to the problem as soon as possible. Else, you may get stranded in an undesirable location in the countryside.   

How to Replace a Blown PCM Fuse

Here are steps to replace a blown PCM fuse:

Materials needed:

  • A flashlight
  • A flathead Screwdriver
  • Protective gear (goggles and gloves)
  • A pair of pliers
  • Replacement fuse

Step 1: Switch off the engine and locate the panel: The first thing to do is to switch off your car engine and allow it to cool off for a few hours. Locate the fuse panel. Typically, the PCM is located beneath your steering wheel or in the engine compartment. In other vehicles, the PCM fuse panel is under the car seats, in the car trunk, behind the kick panels or under the passenger floorboard. But you may need to consult your owner’s manual to find the exact location.

Step 2: Remove the panel lid: Take off the panel lid to see various fuses with their amperages rating, in a range of colors.  Check the diagram behind the panel or the circuit box labeling to know which fuse is assigned to the PCM.  

Step 3: Find and remove the blown PCM fuse: Look for the blown fuse. A melted fuse is usually a discolored, black component; it can also be a cloudy, broken metal filament. Unscrew and take off the blown fuse

Step 4: Replace the bad Fuse: It’s time to replace the old fuse with a new one. While replacing the fuse, make sure you use the same PCM fuse of equal type, rating, size, and amperage. Otherwise, you’ll be shortchanging the power of your vehicle.

Step 5: Check if the new fuse works: Start the engine to test if the entire process works.

Can I Repair my Car PCM Fuse?

My straight answer is no. You can neither reset nor repair a PCM fuse or any other auto fuse for that matter. The best thing to if you have a blown PCM fuse is to replace it. The good thing is that it doesn’t cost an arm and a leg. With $10-$30, you can get a top-quality PCM fuse that will last a long time.  

Final Thoughts

The PCM fuse is central to the functioning of your powertrain control module. More importantly, a blown fuse will ground your vehicle and journey. Replacing your car’s PCM fuse isn’t an action you do often, but usually when you’re replacing the PCM itself. Go for a recommended PCM fuse, one that’s suitable for your car. I’m sure you now know how critical a PCM fuse to the health of your car is. I hope you can make an informed decision the next time you need to replace a blown PCM fuse. Have a safe trip!