ECU Failure Causes, Symptoms & Repair

ECU failure can cause driving performance and even safety driving issues. At this point, car owners must know the symptoms and the causes. Identifying the problems earlier can prevent you from spending thousands of dollars on repairs and replacements. An Obd2 Scanner For Japanese Cars can tell you the problem by retrieving the DTCs. Here, you can learn the causes, symptoms, and repair guide of ECU failure.

What is ECU?

In a vehicle, the electronic control unit (ECU) is the component that controls a certain function. Depending on the corresponding function, various parts of the car send input to the ECU. Data connectivity is required for ECU to operate the chip that runs the firmware and software. Today, ECU controls pretty much every function in your car from the engine related to security and passive safety.

Bad ECU Ground Symptoms

ECU Ground Symptoms

The ECU is in charge of nearly all of the car’s systems and operations. While the Best Foxwell Scanner can be helpful, there are a slew of ground symptoms that would appear if your ECU ever failed. In no time, you’d deduce the ECU was to blame.

1. MIL or Check Engine Light Coming On

The illuminating MIL on your dashboard is the simplest way to tell whether your car has a problem. If the check engine light is on, there are a number of possibilities including a faulty ECU. However, it is important to note that the Check Engine light will come on quickly if the ECU detects problems with any of its sensors, circuits, or other parts.

In some cases, the ECU would mistakenly detect the actual problem. At this point, you need to search for specific issue codes using a scan tool like Autel MS908CV to determine which part of the ECU is currently malfunctioning. 

2. Misfiring or Stalling Engine

The misfiring and/or stalling engine is another symptom of a faulty ECU that triggers the check engine light. There won’t be any uniformity in these matters. In order to detect a specific engine issue, whether it’s misfiring or stalling, you need to retrieve the DTCs. 

This is frequently the result of an engine control module malfunction, in which case the engine is receiving inaccurate data or signal. A worsening condition could lead to decreased engine performance or even wrecking in the long run. 

3. Decreased Mileage

The faulty ECU might not be able to grasp how much fuel to provide to the combustion which makes the air-fuel ratio improper. This indicates that during combustion, an excessive amount of fuel is frequently given to the fire. A rich engine and excessive fuel consumption are the inevitable outcomes. You’ll have to spend more money on gas and create more pollution than usual. 

4. Decreased Engine Performance

A defective ECM, on the other hand, could result in an insufficient supply of fuel for combustion as previously mentioned. Because of this, your car won’t accelerate as quickly as it used to. There’s a chance it will vibrate or even shake, especially if you’re trying to climb a steep hill or tow a large object. If you don’t have enough fuel, you may also notice roughness when the engine idling. 

5. Car’s Engine Can’t Start

One of the most alarming signs is when you completely fail to start your car. It may take a while to get going, but once it does, it won’t stop. A full breakdown of the ECU can result in this condition.

At this point, there will be no computer system for the engine to direct and manage its own operation after that. Even though you can still turn the key in the ignition, the car won’t start since the computer isn’t providing it with the necessary data.

It’s also possible that there are other reasons why your engine won’t start. Using a scanner like Innova 3100 or inspection by a licensed auto technician is the only way to determine if this problem is due to the ECU failure.

Common Causes of  ECU failure

Common Causes of  ECU failure

There are numerous internal factors that could be responsible for this. A faulty ECU can be caused by any of the factors below. As soon as you find issues with the ECU, you should check and respond to them immediately.

  • Wrecked Battery: Your ECU will fail quickly if any of your automobile battery’s cells are dead. Batteries should contain healthy cells to power ECU. Battery death occurs when all of the cells in the battery are dead. At that point, your car will be unable to run since the ECU can’t operate. Starting the engine isn’t even possible in this condition.  Examine your batteries as soon as you see any early warning indications of an ECU problem.
  • Corrosive Components: The automobile manufacturer seals the ECU to keep moisture out. These seals, however, wear out after a few years of use. Moisture will eventually be able to enter the ECU more easily if the seals are too worn. Consequently, corrosion will build on the ECU’s components if the ECU is exposed to moisture. This condition, when left untreated, would damage your ECU and cause it to stop working. 
  • Incorrect Voltage Condition: The voltage range of ECU can operate between 9-12 volts. The lower or higher voltage would make the ECU fail to operate.  Inspect the voltage of the ECU’s wiring harness by using a voltage meter. This gadget will be able to tell how much electricity the ECU should receive. You may have a problem with your ECU once it has lower or higher voltage(lower voltage is more common). 
  • Jump Start Miscarriage: You must always double-check the connections of the jumper cables while performing a battery jump start. Incorrectly connecting the jumper wires to your vehicle’s ECU can cause it to overheat, shorting out the ECU. At this point, you’d likely need to repair or even replace the whole ECU. The costs here can easily run into the several thousand-dollar ranges.
  • Faulty or Incompatible Starter Motor: Sensors built into the starters of many automobiles are becoming more common. The voltage to ECU is controlled by one of those sensors. The correct voltage would be unable to reach the ECU if this sensor went bad. Afterward, it would break down and create even more trouble for your car to occur.

On the other hand, a starter motor that is incompatible with the ECU of your vehicle could also cause issues. Purchase a starter with sensors that can communicate correctly with your ECU before making a purchase.

ECU Damage Top 10 Reasons: Why Your Car’s Engine Control Unit is Bad, Dead, or Faulty! – YouTube

Replacement Cost & destinations

Replacing the ECU in your vehicle could be very pricey. Depending on your car’s make and model, the item alone can cost anywhere from $1,000 to $4000. It is fortunate that in many circumstances, an ECU is repairable and re-programmable so a replacement won’t be necessary.

Service Center or Auto Shop

To have the ECU examined and tested, you should expect to pay anywhere from $120 to $400 at the service center or an auto shop. Repairing or reprogramming a defective ECU might cost anywhere from $250 to $800 depending on the car’s make, year, and model.

You should add roughly $450 to $650 for programming and installing the new ECU if you ever need to replace it, outside the ECU unit cost. 

Online Providers

Today, you can also get ECU repairs or replacements from online providers. You can send your broken ECU to these providers for repair at their location. They ship the repaired ECU back to you.

Online ECU reprogramming or repair for numerous vehicle models costs between $250 and $450. On the other hand, there might be providers that sell their services on auction sites and may do the job below $100.

Final Discussion

The faulty ECU can be caused by one or more factors. Since it controls many fundamental functions of the vehicle, the faulty ECU would affect those functions as well. You’d likely notice symptoms when the ECU becomes malfunctioning.

However, a scanner like Foxwell NT809 or professional help might be required to determine the actual problems with ECU. Replacing ECU can be costly but it can be repaired and then reprogrammed by a professional.