7 Symptoms Of A Bad ECU And What To Replace To Fix ECU

Symptoms of a Bad ECU are comparatively hard to diagnose because an Engine Control Unit (ECU) is the brain of your car. Diagnosing a bad ECU computer is not possible by looking at them; you have to check some of your car components and testing.

But, knowing some most common symptoms of a bad ECM will help you a lot. Knowing your ECU is bad is not enough because you must take steps to fix your bad Engine Control Module (ECM) as fast as possible because your vehicle won’t operate properly with a faulty ECM. So, let’s see what the symptoms of a bad engine control module are and what to replace to fix a bad ECU.

Symptoms Of A Bad ECU

Whether your ECU is bad or it’s not working, a Check Engine warning always helps you. You also notice poor engine performance if your car ECU is bad because the ECU computer is steering the car engine. Both of the signs are the most common symptoms when you have a faulty ECU in your car.

The engine control unit (ECU) is also known as the engine control module (ECM). An ECU is an electronic module that maintains the engine function in the vehicle. ECM gets data from some electronic components and sensors of a car and uses that data to control the car engine. That’s why if your car ECU computer goes bad, it affects the whole vehicle performance.

symptoms of a bad ecu
Symptoms Of A Bad ECU

By mechanical analysis and some of the manufacturer’s engineering experiences, they come up with some of the most common symptoms that will help you detect ECU conditions.

Here are some most common bad ECU symptoms :

  1. “Check Engine” Light Is On
  2. Loss of Acceleration
  3. Car Won’t Start
  4. The drop in Fuel Economy
  5. Poor Engine Performance
  6. ECU getting Overheated
  7. Car Engine Stalls or Misfires

These are the seven most common symptoms of a bad ECU, and you have to check those signs to be certain your car ECM computer is going bad.

1. “Check Engine Light” Is On

Of course, there can be many reasons why your car ECU goes bad. The “Check Engine Light” will notify you with warning lights on the dashboard whenever something happens to the car’s engine control unit.

Seeing the “Check  Engine” warning lights on is the most common sign that tells your car ECU Goes bad. But, you have to check why the Check Engine light comes on because there can be other reasons behind Check Engine lights on.

Check Engine Light Is On
Check Engine Light Is On

Get an OBDII sensor and reveal the issue that makes ECU bad. If there is something wrong with the engine control unit, the Onboard Diagnostics II (OBD2) will show some of the code, and you need to address them properly. When the check engine light is on, that means the defective circuit, sensor, or electronic component needs to be checked.

2. Loss of Acceleration

It’s always easy to notice if you have less acceleration in the car. The engine control unit (ECU) is directly connected with the transmission control module (TCM) because the ECU computer helps the TCM make proper adjustments for your car’s acceleration. That’s why you will notice a loss of acceleration if your car’s ECU is bad.

The engine control module (ECM) gating data, and with that data, ECU adjusts the throttle accordingly, smooth and effortless shifting of car transmission. So, it’s obvious that if the ECU is defective, it won’t be able to adjust your car’s transmission, and you will experience less power of acceleration.

3. Car Won’t Start

The engine control unit has controlled all over the car. So, the ECU computer needs to be working properly in order to start the engine and run it. Your car can fail to start if your car computer does not work. The car doesn’t start a very common symptom that tells you a car is having issues with the engine control module (ECM).

If your car doesn’t start, you should check the other components first. Check the car battery connection, starter, and other essential components, but if you don’t get the clue, you must check the ECU in your car. To test the ECU or ECM, you should have some experience. If you don’t have any knowledge or experience about the car computer, you should not do it yourself, get a mechanic, and leave it to them.

4. The Drop in Fuel Economy

Whether you say poor fuel economy or bad gas mileage, or a drop in fuel economy, all of them are the same thing. As I said earlier, the ECU is the brain of a vehicle. An ECU gathers data from the vehicle’s sensors and electronic components, and using this data; the ECU controls the whole car. So, when ECU is not well or won’t understand collected data from the sensors, it’s so obvious that the ECU won’t be able to maintain the air-fuel ratio. And eventually, you will experience a drop in fuel economy or bad mileage.

If you notice you have bad gas mileage, you should check the car computer because a sudden drop in fuel economy is also a strong symptom of a bad ECM. After noticing poor fuel economy in your car, you should take steps as soon as possible.

5. Poor Engine Performance

As a car owner, you might know that if your car’s combustion chamber doesn’t get the engine fuel, then the car engine performance will decrease and in the long run it can ruin a car engine. Car engines cannot get enough fuel to the combustion chamber for various reasons, but one of them is a bad ECU.

Noticing poor engine performance is easy because if your car engine performance goes down, the car will shake and vibrate. Poor engine performance is a very strong symptom of a bad engine control module.

6. ECU getting Overheated

Car ECU gets some normal heat from the processors, transistor, or chips. But, your car ECU computer frequently gets overheated. This is not good for your ECU because overheating can damage the ECU. Overheated ECU can bring some issues in the vehicle because an overheated ECU can’t control the vehicle properly.

The car ECU will be defective if the engine control unit gets excessively heated frequently. Check the heating level or temperature of your car ECU computer. Some code can appear if your car ECU gets overheated.

7. Car Engine Stalls or Misfires

Frequently car engine stalls or misfires for a bad or faulty engine control unit. But, there can be other reasons why your engine misfires or stalls. To specify whether your car ECU or other components for making engine misfires or stalls, you have to check ECU and other components in the vehicle.

If your car engine stalls or misfires for ECU, that means your engine control module gets false data from the sensors. Car engine misfires or engine stalls can make a car’s performance so poor. So, if your car has an engine misfire or stalls issue, you have to have an engine control unit tested by a professional.

How To Repair A Faulty ECU

Repairing or fixing a faulty engine control unit (ECU) can be very hard for you if you don’t have previous experience and not enough knowledge about the ECU. And repairing a defective ECU is not that easy. Without proper knowledge regarding the engine control module (ECM), you should not try to fix or repair the ECU by yourself. Leave your ECU to a professional if you want to fix that.

Here are some recommendations for replacing, testing, and fixing your ECU :

  • Ignition coils
    The vehicle ignition coil transforms the battery’s voltage all over the vehicle’s electric system from the vehicle’s ignition system. If you have a faulty ECU in your car, then you have to check the Ignition coil to replace or fix it.
  • Faulty spark plugs
    Faulty spark plugs might need to be changed or repaired when your car engine control unit is not working properly.
  • Fuel Injection
    Test fuel injection when your vehicle has a bad ECU. But you have to test or check the Fuel injection properly.
  • Mass Air Flow
    Check the mass airflow in your vehicle. Make sure the mass airflow or airflow is working properly in your vehicle.
  • Throttle position sensor (TPS)
    The throttle position sensor (TPS) is directly connected with the ECU. That’s why to fix or repair the ECU; you have to test the throttle position sensor.
  • Idle air control valves
    The Idle air control valve is also known for IAC. Test the Idle air control valves to look for an issue that is preventing the ECU from working.
  • Test grounds with a multimeter
    Testing grounds with a multimeter is the best way to test or check the grounds in the car. That’s why we recommend you test grounds with a multimeter if you want to fix a bad ECU.

Like we mentioned earlier, repairing a faulty ECU is not easy. No matter how long you’ve been driving, you have to have proper knowledge and experience to fix a bad ECU. A mechanic can always help you to repair a faulty ECU.

ECU Replacement Cost

If your car ECU goes bad, then it will need to be replaced or reprogrammed. The replacement or reprogramming of the ECU is not cheap; it’s way more expensive. A faulty ECU repair can cost you about $1500 to $2500, and the ECU repairing cost depends on the car’s model.

An ECU computer is one of the expensive components. On average, replacing the Engine control unit can cost you around $500 to $2000 only for ECU. And the ECU replacement labor cost can be between $100 and $300.

Typically for the entire ECU replacement cost goes up to $1000 on average. But you have to keep in mind that the engine control module is different for every model. A luxury car’s ECU is different from a low economy car. That’s why ECU replacement costs vary on your vehicle.

Final Thought

There can be many symptoms of a bad ECU. But we shared the most common symptoms of a bad engine control module. If you notice these signs in your car, you should check the ECU properly. Waiting for the ECU to be fixed automatically can be a foolish thing to do because a faulty ECU will bring more issues in your car that put your car in real danger. So, after noticing a car has an ECU issue, you must try to repair or fix the ECU as soon as possible.

Repairing an ECU is not for everyone. If you’re only a car driver, then you should not try to fix or repair the ECU. You should bring your car to an auto mechanic to fix your car ECM for you because an auto mechanic has the experience and proper knowledge about the engine control unit. If you try to repair the ECU by yourself, it can be more difficult for the mechanic to fix it. So, whether your car has a bad ECU or you want to repair the ECU, you should contact a mechanic for better service.

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