Engine Control Malfunction (Causes, Solutions + More)

Engine Control Malfunction

There are some components in your car that do a whole lot of different things, and they can be particularly problematic if they stop working or start having issues.

If you encounter an Engine Control malfunction, or an amber engine warning light, then you need to know what it means and how to solve it.

The Engine Control Unit (ECU), otherwise known as the Engine Control Module (ECM) is responsible for controlling the actuators that enable your engine to run efficiently and effectively.

When it is not working properly, it may need resetting, it may need repairing, or it may need replacing entirely.

Here are a few steps you need to take to fix an engine control malfunction, which includes:

Step 1: Try Resetting The ECU

Step 2: Use A Diagnostic Tool To Find The Fault Code

Step 3: Contact A Professional

Step 4: Get Your ECU Tested Regularly

Step 5: Try Remapping The ECU

What Is The Engine Control Unit?

To understand what we might need to do to get this piece of kit running normally again, we first need to know what it actually is and how it works.

The ECU is a surprisingly complicated piece of electronic equipment that is essentially in charge of monitoring the conditions that the engine is operating under and controlling the timings of the basic processes that need to happen in order for the engine to fire and your car to work.

It is sort of like a very basic form of CPU. It is constantly receiving information about what is going on inside the vehicle, interpreting that data, and outputting commands to different parts of the engine to make sure it is running smoothly and efficiently.

There are a few key things that the ECU controls, all of which are pretty essential for the normal functioning of your car, such as:

Air-Fuel Ratio

To make the engine run, fuel needs to be injected into the cylinders and the primary role of the ECU is for determining how much and exactly when the fuel gets injected for maximum efficiency.

If it is not able to do so accurately, the engine can run rich (with too much fuel and/or too little oxygen, causing the combustion to be wasteful and dirty) or lean (with too little fuel and/or too much oxygen, causing the combustion to have less power).

Idle Speed

Most engines also rely on the ECU for idle speed control and to provide the basic functions of cruise control and top-speed limits.

The ECU monitors the engine’s RPM and controls the fuel injection, spark events, and valve timings in order to do this.

Variable Valve Timing

In some engines, the ECU is also able to control the time at which the valves in the engine open depending on how quickly the vehicle is moving.

This helps to increase the airflow in the cylinder and improve both fuel economy and overall power output.

ECU Sensors

In order to know what it needs to do for each of these functions, the ECU takes into account many variables like the engine demand, the engine/coolant temperature, the air and fuel temperature, the fuel quality, the filter restriction, the air pressure, and the pumping efficiency. To do this, your ECU relies on a significant number of different sensors such as:

  • MAP: Manifold Absolute pressure.
  • IAT: Intake Air Temperature.
  • MAF: Mass of Air Flow.
  • CKP: Crank Shaft Position.
  • CMP: CAM Shaft position.
  • ECT: Engine coolant temperature.
  • O2: Oxygen sensor.
  • TP: throttle position.
  • VSS: Vehicle speed sensor.

Knowing all of the moving parts involved in making the ECU work, and all of the various jobs that it does, you won’t be surprised to hear that there are a lot of ways that it can go wrong.

Problems with the ECU are very hard to diagnose and can require a huge variety of different fixes in order to solve them.

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How To Fix Engine Control Malfunction

If you have figured out that there’s something wrong with your ECU, what can you actually do about it? You can try resetting it, which might solve the problem yourself, but if it needs repairing or replacing then you may need to hand it over to a professional.

Step 1: Try Resetting The ECU

The first thing to try is resetting the ECU. It might be that your Check Engine Light has come on because of a minor fault in the electronics that can be resolved by simply turning the unit off and then on again.

To do this:

  • Open the bonnet of the vehicle.
  • Locate the fuse box.
  • Find the fuse that is labeled “ECU”.
  • Remove the fuse and then put it back.

Step 2: Use A Diagnostic Tool To Find The Fault Code

If the problem persists, you can get more information by using an independent diagnostic tool to find the specific fault.

These tools are relatively inexpensive and read information from the vehicle to give you a code that refers to the exact problem that is occurring.

You may be able to resolve the fault yourself but, if not, it will at least tell you exactly what you need to get fixed before you speak to a mechanic.

Step 3: Contact A Professional

If resetting the ECU doesn’t work, and you can’t find a quick fix using a diagnostic tool, then it’s time to talk to a professional.

Most ECU problems require repairs or replacements to resolve them, and this simply isn’t a job for an amateur.

Step 4: Get Your ECU Tested Regularly

To make sure that you’re not dealing with ECU problems too often, then you should be getting the unit tested on a regular basis. It’s a quick and easy thing for a professional to do and usually costs around $100.

Step 5: Try Remapping The ECU

If you want to get more out of your ECU, you can get it remapped. This is basically a reprogramming of the way that it functions to improve performance and get more out of the unit.

Doing this can, however, reduce the lifespan of the ECU and it may invalidate your manufacturer’s warranty.

It usually takes about an hour for a specialist to get this job done and can cost anywhere from $200 to $800 depending on how complex the unit is.

Engine Control Unit vs Electronic Control Unit

Before we go any further, we should definitely talk about something that often gets confused when we’re talking about the Engine Control Unit.

There is another component that is found in most modern cars known as the Electronic Control Unit or the Electronic Control Module, which is confusingly referred to by the same acronyms, ECU and ECM.

The Electronic Control Unit is a larger system that contains all of the different units that control every electrically-operated aspect of the vehicle. Your Engine Control Unit is normally found inside the Electronic Control Unit, which can also house:

  • Powertrain Control Module (PCM)
  • Transmission Control Module (TCM)
  • Brake Control Module (BCM or EBCM)
  • Central Control Module (CCM)
  • Central timing module (CTM)
  • General Electronic Module (GEM)
  • Body Control Module (BCM)
  • Suspension Control Module (SCM)

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How Do You Diagnose Engine Control Problems?

So, how can you actually tell that there is some kind of problem with your Engine Control Unit? There are a few key things that might tip you off that it is not functioning as it is supposed to.

Check Engine Light

The first indication that something is wrong is normally when your Check Engine Light comes on. This doesn’t always mean that it is the ECU that is having problems, but it is one of the most common reasons why you see this warning.

Though it can differ between individual vehicles, an amber light normally means that there is something wrong with your emissions system, a flashing light means that the engine is misfiring, and a solid red light means that something is seriously wrong that needs immediate attention.

Lower Fuel Economy

This is another common sign that something might be wrong with your ECU, as it has a significant impact on how efficiently your engine is able to utilize fuel.

If you notice that you’re not getting as many miles to the gallon as you’re used to, then the ECU might need adjusting or repairing.

Poor Performance

If you’re noticing that you’re not getting as much power out of your engine as you’re used to, this can be an indication that the ECU is not doing its job properly.

Lagging or Surging

If your engine is slow to gain power or surging in power at random intervals, then it might mean that your ECU is not controlling the fuel injection timings properly. It may be putting in too much or too little at a time, leading to an inefficient fuel-air ratio.

Misfiring or Stalling

Misfiring and stalling are often problems with the spark plugs – which may wear down or become damaged over time.

However, it might not be the spark plugs themselves that are the problem; it could be the ECU that is controlling when and in what order they fire.

The engine might stutter as you accelerate or stall more frequently when you’re idling because the ECU is not firing the spark plugs at the right time.

Not Starting

If the ECU fails completely, then the car might not start at all. Without a functioning ECU, fuel is not going to be injected into your engine and it’s just not going to work.

Common Repairs for Check Engine Light Issues

Depending on the cause of the check engine light, various repairs might be necessary. Some common repairs for check engine light issues include:Oxygen Sensor ReplacementGas Cap Replacement or TighteningCatalytic Converter ReplacementMass Airflow Sensor ReplacementSpark Plug Wire Replacement

It’s essential to consult a professional mechanic to accurately diagnose and repair the issue causing the check engine light to come on.

Importance of Timely Repairs and Maintenance

Addressing the check engine light and any underlying issues promptly is crucial for the health of your vehicle’s engine and emission control system.

Timely repairs and maintenance can help prevent more extensive, expensive problems down the road and ensure your vehicle runs efficiently and safely.

How much does it cost to fix an engine control system?

The cost to fix an engine control system can vary depending on the make and model of the vehicle and the severity of the issue. Generally, the cost can range from a few hundred dollars to over a thousand dollars.

It’s important to note that if the engine control system is causing the car to go into limp mode, it’s best to refer to a professional mechanic for a proper diagnosis and repair. Attempting to fix the issue yourself can potentially lead to further damage to the vehicle’s components.

How do you reset engine control?

To reset the engine control module (ECM), there are a few ways to do it. One way is to disconnect the battery cable for 2-3 minutes and wait to see if the ECM resets itself. Another way to reset the ECM is by disconnecting the battery and removing the fuse related to the engine control module.

You can also reset the ECU by driving the car for 15 minutes, disconnecting the battery, waiting for at least five minutes, pressing and holding the brake for 20 seconds, and then reconnecting the cable. Keep in mind that the specific steps may vary depending on the make and model of the vehicle.

It is best to refer to a professional mechanic for a proper diagnosis and repair if the engine control system is causing the car to go into limp mode.

Amber Engine Warning Light FAQs

How Much Does It Cost To Fix Engine Control Unit?

Depending on whether your ECU just needs a simple repair or it needs replacing entirely, the cost can vary. On the cheaper side, repairs can be as little as $300-$400, but a full replacement can end up costing as much as $2,000 or more.

Can I Drive With A Faulty Engine Control Module?

Your ability to drive with a faulty ECU depends entirely on how bad the issue is. If it is not working at all, then you may not be able to get any kind of fuel injection and no power to the engine – and serious problems can make it extremely unsafe to drive.

If the ECU fault is only minor, you might be able to drive normally, but it can be hard to tell how severe the issue is.

What Happens When The Engine Control Unit Goes Bad?

When your Engine Control Unit stops functioning normally, it can cause a lot of problems. You might notice the engine surging or lagging, you might notice misfires or intermittent stalling, you might get worse performance and fuel economy, or you might not be able to start the engine up at all.

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So, what is an Engine Control malfunction, and what can you do to fix it? The Engine Control Unit is responsible for managing many aspects of how your engine functions, such as when and how the fuel is injected into the cylinders.

When it stops working properly, you can try resetting the ECU but you will usually need to call a professional to carry out any repairs that need doing.

To keep your ECU functioning at its best, make sure to get it tested regularly, and you can try remapping it to improve its performance.



Steve P.

Steve is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Riviera. Steve is based in Boise, Idaho.

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