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How to Know If You Need an ECU Repair?

November 17, 2021
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How to Know If You Need an ECU Repair?

Engine Control Unit (ECU) is a vital part of a car these days, functioning as a part that controls the drivability and performance of the engine. A faulty ECU can be a nuisance as it can cause the car to be inefficient or sometimes even undrivable. ECU repair should be done immediately but best done by professionals as it is a complicated electronic task.

Causes of ECU failure:

The engine control unit manages the production of power for the car by controlling ignition spark and fuel injection in the engine. It monitors the mixture of air and fuel to make the engine running at an optimal level and prevent power issues. A few familiar reasons for ECU failure are the following:

Fuel solenoid
The connection between the ECU harness and the solenoid can be jeopardized if the solenoid has corrosion or any faults as it may cause wire shortages and the inability of connection.

Rust, moisture, and heat
These environmental factors are causes of an ECU becoming faulty as they limit or sometimes stop it from functioning. Its internal body can also become a target of moisture affecting its plugs and risking circuit board shorting. Heat can also similarly cause damage to internal parts.

High voltage
The high voltage being directed from the car’s charging system may exceed the limit the ECU is designed to handle in result affecting its performance. Charging system faults are a completely different story.

A faulty or incorrect starter can bypass the override sensor, which will in turn not control the voltage being transmitted to the ECU. If the starter has been recently replaced, then there are high chances that it is the cause of ECU failure.

Jump starting
Jump starting if not done properly can cause a surge in the power provided to the ECU and this may cause wires in the ECU to short out. Making sure that the process of jump-starting is done correctly is important.

Symptoms of a bad ECU

An ECU is responsible for monitoring several different sensors in the car. By monitoring them it ensures optimal performance but if the ECU is faulty then other parts can also suffer. These are some symptoms of a bad ECU:

Illuminated check engine light
The check engine light is illuminated if the computer senses issues within its parts. Scanning it can reveal what was the cause of the illumination.

Stalling or misfiring engine
This is the result of a defective ECU as the engine and ECU are not functioning smoothly resulting in the performance being affected.

Poor performing engine
The fuel supply to the engine can be disrupted because of a faulty ECU, this will cause the car to face trouble while accelerating. This is more prominent when there is added weight in the car or it is going uphill

Car not starting
If the car is facing difficulty in starting or not starting at all it may be due to a faulty ECU. The engine does crank but will be unable to start as the ECU will not be working hence the inputs to start the car will not be available.

Poor Mileage
When there is a fault in an ECU, chances are that it may not be able to monitor and send the accurate amount of fuel to the engine. It can be sending too much fuel resulting in poor mileage by the car.


ECU repair

Multiple parts in the car will show symptoms of a faulty ECU. However, some symptoms like misfiring and check engine light may not be due to another component instead of the ECU. So, if one believes that the ECU is faulty then getting it tested is the way to go. ECU repair can be done in various ways:

  • An electrician can repair the ECU if the fault is due to a short or bad connection in the wires of the ECU or the plugs in it.
  • Disassembling the ECU completely is sometimes needed because it may require detailed electronic work to fix the ECU.
  • ECU can also get affected by bugs in its software so resetting it to its factory-recommended setting or flashing its firmware may be needed.
  • If there is physical damage, then chances are that it is beyond repairing and it will be needed to be replaced.

Replacement of ECU and its cost

If it is certain that the ECU must be replaced, then it will be important to know how much it costs. Each car and its model have its own ECU, so if the car and make is very advance and expensive, chances are that so is the ECU.

It is advised that refurbished ECU are bought with extreme care. A new ECU in an economy car can cost around $900 to $1100. The cost of parts may vary from $400 to $1400 and for reprogramming and installation, the labor cost could be from $100 to $200.

ECU Repair: Conclusion
Although mostly ECU’s last the lifetime of the car but eventually sometimes, they need repair or replacement around 80,000 miles if they gradually become faulty. It is recommended that ECU repair be done by professionals and is handled with care.

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