Common ECM/ECU Problems

OEM ECMThe ECU (Electronic Control Module, aka ECM or Engine Control Module) is a crucial component in a modern car. If it fails, your car won’t run at all. To help you avoid getting stuck by the side of the road, we cover the common symptoms to look for in failing ECUs and what can cause them to fail in the first place.

How Do You Know If Your ECU/ECM Is Working Fine?

Your ECU is constantly checking and adjusting engine settings from the moment you turn the key. If it is working properly, your car should function as normal. For more information about what an ECU/ECM is and why it is so important read our blog here.

  • The car starts the first time and idles smoothly
  • No hesitation when accelerating
  • No warning lights on the dashboard
  • The car feels responsive

If there is a problem with it, there are several symptoms that you will start noticing.

Starting-To-Fail Symptoms

ECM problems

The ECU is a complex device. If the PC board or connector gets damaged, it can start behaving erratically.

If you notice the following symptoms, your ECU may be starting to fail:

  • The check engine light is on: This light goes on for several reasons. If it happens in conjunction with some of the symptoms below, it could well be your ECU that is at fault.
  • The engine shuts off randomly: If the ECU is unable to get the air/fuel mixture right, the engine can cut out unexpectedly.
  • The car won’t idle properly and/or hesitates when accelerating: An incorrect air/fuel mixture will also affect the way your car drives. In most cases it will feel underpowered or stutter as you accelerate.
  • Fuel consumption goes up unexpectedly: If your ECU is providing an over rich fuel mixture, you may notice a sudden drop in fuel economy.
  • Automatic transmission shifts roughly: A modern ECU communicates with dozens of other onboard devices. They control everything from steering to braking and the gearbox. If your transmission changes gears roughly, the ECU may be sending the wrong signals to the Transmission Control Module.

Many of these symptoms can also be caused by other vehicle control units or systems in your vehicle. So, it’s always a good idea to have the car checked by a mechanic or scanned with an OBDII scanner before replacing the ECM/ECU.

Complete ECU/ECM Failure

replace ecm

In some cases, the ECU can fail outright. If this happens, you are unlikely to get the car going until the ECU is replaced.

If you’re experiencing the following symptoms, the ECU may have failed completely:

  • The car won’t lock or unlock with the key: Every car has an ECU that has been coded to its immobilizer. If the ECU is fried, it will not be able to process the signal from your key fob to lock or unlock the doors.
  • The engine refuses to turn over: You may find that the car won’t respond at all when you try to start it. This can happen if the ECU isn’t sending the correct signal (or any signal) to the engine.

In most of these cases, you will also see that the ‘Check Engine’ light is on. On older cars that have less complex ECUs, you may still be able to get the engine to turn over. But if it starts at all, it will run very poorly.

How Can An ECU/ECM Fail?

So, now we know the symptoms, but what are the causes of ECU failure? The modern ECU is a multi-function device that interacts with dozens of onboard systems. Sometimes a problem with one of these can also damage the ECU.

Some of the most common issues with ECUs include:

  • Corroded or damaged wiring – The fuel injector wiring harness can break. If it causes a short in the ECU, then both will need to be replaced.
  • Damaged ECU internals from water intrusion or power surges – Jump starting a car can sometimes damage the ECU. If the ECU housing is cracked, water may get in and damage it.
  • Failed sensors – there are many sensors in a modern car. If one of these malfunctions, the ECU may not function correctly
  • Improper grounding – A poorly grounded battery can damage the ECU and other electrical components

Replacement ECUs/ECMs From Tom’s Foreign Auto Parts

ECM

If you need a replacement ECU for your vehicle, TOM’S Foreign Auto Parts has close to 6,000 quality used ECUs in stock. We cover several popular brands, from Acura to Honda, Infiniti, and much more. Whether you buy new or used, the replacement ECU will need to be programmed to your vehicle – you can read about reprogramming an electronic control unit or engine control module here.

All our used OEM parts come with an industry-leading guarantee. And you can save up to 75% off new OEM prices.

We stand by our products. And have been providing quality used OEM parts for over 30 years. So, contact us online or browse our broad range of quality used OEM ECUs here.