What Are the Symptoms of a Blown ECM Fuse? (Explained)

ECM is broadly known as Electronic Control Module. You can tell by the name that ECM is responsible for ‘controlling’ all engine functions. It is also sometimes called PCM (Powertrain Control Module) or ECU (Electronic Control Unit).

The fuse serves to protect the computer. It is installed inside the ECM. It saves the computer from any damage caused by unexpected electrical surges.  

The fuse takes the trouble on itself and blows up so that the damage does not reach the device. Symptoms of a blown-up fuse can be varied and this article is all about those! I will also discuss how to fix a blown ECM fuse. So read till the end.

Blown Ecm Fuse Symptoms

Common Signs and Symptoms of a Blown ECM Fuse:

Multiple issues arise in case of an ECM fuse failing. It can start from a non-functioning vehicle. And also range over engine not starting, the battery not working, more than usual fuel consumption, etc. 

Car cranking and not starting is attributed to a range of problems. There are specific symptoms that justify a blown fuse though.

A blown fuse is typically associated with a car shutting off. The reason behind this and the symptoms and how to detect a blown ECM fuse are discussed below.  

1. Engine Stopping/Not Starting/Misfiring

The fuse exists within the ECM. When it is blown, the ECM starts falling naturally. The most prominent symptom of a failing ECM is no power when the key is put to start.

A failed fuse cuts off the power and disconnects the entire vehicle from the power source. As a result, the engine fails to start. You may see an absence of the dash lights too. 

Because the ECM controls ignition and other vital functions, the engine misfires or cranks. Ultimately does not start or run smooth. The misfiring, stalling intermittently can be attributed to the faulty computer system as well. 

The misfiring or stalling might be quite unpredictable. Thus, being deemed as erratic occurrences.

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2. Check Engine Light Flashing

ECM is responsible for all-electric components of the vehicle. This includes the check engine light as well. So, when there is a blown fuse, the check engine light may pop up. 

This light flashes as the computer identifies a defect with circuits or sensors. 

3. Bad Fuel Economy

A blown fuse messes with the ECM. In any case, if the fuse is slightly damaged and there’s still some electricity supply to the ECM, it can cause messed up readings.

A failing ECM will miscalculate the amount of fuel the engine needs. To add icing on the top, the engine calculates more than the necessary amount of fuel here. Therefore, the fuel requirement increases. This results in a bad fuel economy. 

At the same time, the power may also reduce. 

Pro Tip: All the symptoms of a blown fuse can be symptoms related to other problems. So, make sure you physically check if the fuse is blown before taking the necessary steps.

What to Do When You Detect A Blown ECM Fuse?

The problem of a blown fuse is becoming difficult to diagnose with just symptoms. This is due to the complexity of modern sophisticated systems. 

The fuse affects the ECM which in turn affects the overall performance of the vehicle. It is necessary to involve a professional to check out the problems.

However, if the fuse is frequently blowing, there are a few things you can do. Let’s analyze these:

Change or Check for Shorts

ECM Fuse Change or Check for Shorts

The wiring that connects the ECM with the battery gets damaged sometimes. This can lead to shorting or ‘short-circuit’ leading to a sudden power surge. 

If the surge is more powerful than the fuse can hold, it blows. In this case, it is necessary to keep the wirings in check of short. However, this task can be strenuous and feel like looking for a needle in a haystack. 

Here, you should consult an expert or a professional. They have devices to detect a short and can easily solve the problem. 

However, you can DIY by making sure all the grounds are clean. Then check for shorts via wiring and resistance.

 Check the wiring going to multiple parts of the engine (fuel injector, pump, ignition coil, ignition module, fuel pump relay, crankshaft sensor, and of course, the ECM). Check the flooring wiring for wetness or rubbing with the seat floor. Those things cause short in the wiring.

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Change Damaged Starter

The energy from a damaged started can channel to the ECM. Consequently, causing a power surge and a blown fuse. 

A clicking noise is a sign that your starter is damaged. So, fix this issue to avoid frequent blowing of fuse. 

Change Damaged Fuel Pump

Overheating due to a damaged fuel pump accelerates the consumption of amperage. If it exceeds more than the fuse’s capacity, it blows.

Replace the bad fuel pump to solve this issue.  

Positioning of the Oxygen Sensor

The sensor’s wiring can create a grounding in contact with the exhaust. As soon as the grounding happens, the fuse blows up.

Read Also: How To Start A Car With A Bad Crankshaft Sensor?

Is Replacing A Blown ECM Fuse Typically Expensive?

Replacing an entire ECM is pretty costly. It starts from $800 and can range from $1500-$2000 as well. Moreover, service charges may include another $100.

However, replacing an ECM is not always necessary for a blown fuse. The cost of a fuse varies. A fuse box may cause around $500.

But just replacing a fuse is usually a lot cheaper.

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How Often Should You Inspect or Service The ECM Fuse?

Keep a weekly check of the wiring for shorts. A short circuit can blow the fuse and drain the battery as well. 

However, checking the fuse is not necessary this frequently. You should check if the vehicle has performance problems. If the vehicle does not start or cranks, check the fuse. 

An ammeter and voltmeter should be included to check amperage and voltage often. This practice on a weekly or monthly basis is fine.

Final Thoughts

The blowing of fuse is pretty common. But it is also a pretty simple problem with a simple solution.

Unlike faulty ECM, it is not a big problem or an expensive problem. So my advice to you is, if you take preventive measures and look out for shorts, you are good to go!

Read Also: What To Do After Replacing MAF Sensor & When To Replace?

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