Five Signs That Your ECU Is Not Working (and How to Replace It)

It is also known as the engine controller unit (ECU), engine control module or ECM. This crucial part of modern vehicles is vital. This is the computer that controls the engine and the powertrain. It ensures the vehicle runs as it should.

An engine control unit can go bad and cause a variety of symptoms that make it hard to drive the car in its intended manner. Let's take a look at some of the symptoms, and then we will discuss the costs involved in replacing the ECU. Let’s begin with a quick look at the signs:

A stalling engine and a check engine lamp on the dashboard are two of the most obvious signs that an engine control unit has failed. There may be changes in fuel consumption or problems with starting your car. A decrease in engine performance may be another possibility.

Below is a list that explains the symptoms most commonly associated with a bad engine control system.

Bad Engine Control Unit (ECU), Symptoms

1. Verify Engine Light

Check Engine Light is the most obvious sign of an ECU problem. The Check Engine Light will come on regardless of whether the ECU is faulty.

The OBDII scanner will help determine whether the issue is with an engine control unit. A defective sensor, circuit, or other electronic component could cause the problem. To pinpoint the problem, look up the trouble codes. 

2. Engine Stalls

If the ECU is failing, you might notice trouble with your car’s idle. The ECU could be causing your vehicle to stall or start misfiring while you wait at traffic lights. 

It is possible that the pattern of stalling or misfiring may be totally random. There are no patterns to help you troubleshoot. The problem could be caused by an ECU that is not working properly, sending incorrect information to the engine. This may lead to too much fuel and air being introduced to the engine. 

3. Poor Fuel Economy

With an imbalanced air/fuel ratio, the engine won’t run optimized. You might spend longer filling up the tank if the ECU accidentally sends too much fuel to your combustion chamber.

That’s why it’s important to keep track of your fuel economy, so you can get a heads up when a problem exists. Additionally, more fuel consumption can lead to environmental harm. 

4. Reduced Engine Performance

The malfunctioning ECU could also cause the ignition chamber to not get enough fuel. This can lead to performance problems.

It is possible to step on the accelerator and not get any response. If you're towing or climbing inclines, your vehicle may vibrate. It’s best to replace the ECU before your vehicle stops performing at all. 

5. Car Doesn’t Start

The worst thing that could happen because of a failed ECU is to have a car that won’t start. You might initially notice that it is more difficult to start the engine, until eventually it stops. 

While having a non-running car can mean many things, it’s also a symptom that the engine control unit has failed completely. Without any signals being sent to the engine, it simply doesn’t know what to do. 

Locating the Engine Control Module

The engine control unit can be found close to or at the engine. It can be found underneath the dashboard, or behind the glove compartment in some vehicles. 

However, there’s not just one place where the ECU can be found. That’s why it’s essential to check the service manual if you need to find your car’s engine control unit. 

What is an Engine Control Unit?

The engine control module processes information from sensors all around the vehicle, and then sends that data to the motor. It processes information such as engine spark, fuel-to-air ratios and other data. 

It’s a critical component of any modern vehicle, where most of the essential functions are handled by the ECU. If the engine control unit starts to malfunction, any number of problems can occur, to the point where the car won’t work at all. 

RELATED : 5 Signs That Your Engine Control Module (ECM), Is Not Working

Repair of Engine Control Unit

With most vehicles, the cost to replace an engine control module is approximately $500-$2000. Expect to pay between $450-$1800 for an ECU and $50-$200 in labor fees.

Although you can sometimes save a little money by replacing the ECU yourself, most of the cost of repair is related to the component.

In some cases, it’s possible to reconfigure or reprogram the ECU. If that’s possible in your situation, you won’t need to purchase a new engine control unit but will simply have the labor expense. 

You will also need to pay for the ECU to be diagnosed by your local shop. This could run up to $100-$300 in some instances. However, if you have an OBDII scanner and don’t mind doing a little online research, you might be able to diagnose the problem yourself. 

The cheapest cars to fix are economy models. An ECU that is complex will be more expensive if you own a luxury vehicle. While it might be tempting to purchase a used ECU to cut down on the costs, this isn’t a good long-term option. You will have to have the ECU reprogrammed if it fails prematurely. 

Some engines control units cannot be reprogrammed by you, and it can prove very challenging to do so. It is best to consult your dealer before trying to swap it.