Symptoms of a Bad Automotive Engine Computer (ECM): How to Diagnose ECM Failure

Introduction

The Engine Control Module (ECM) is a vital component in modern vehicles, responsible for managing engine performance, fuel economy, and emissions. When the Engine Computer starts to fail, it can lead to a range of issues that may affect drivability and safety. In this guide we will dive into the most popular symptoms of a failing engine computer.

Bad Engine Computer Symptoms

1. Check Engine Light: The engine computer is part of a vehicles CAN BUS network which exchange data with other various modules such as the TCM (Transmission control) and ABS (Antilock Brake System). Of course when the computer sees a problem the check engine light is illuminated, but there are a list of codes that will let you know the engine computer itself is bad.

• P0600 - Serial Communication Link Malfunction
• P0601 - Internal Control Module Memory Check Sum Error
• P0602 - Control Module Programming Error
• P0603 - Internal Control Module Keep Alive Memory (KAM) Error
• P0604 - Internal Control Module Random Access Memory (RAM) Error
• P0606 - ECM/PCM Processor Fault
• P0607 - Control Module Performance
• P0610 - Control Module Vehicle Options Error
• U0100 - Lost Communication with ECM/PCM

The last code is the only code that does not point directly to the engine computer failure. The U0100 - Lost Communication code could mean a simple fuse is blown, or a bad ground circuit causing the computer not to turn on.

2. Bad Fuel Injector or Ignition Coil Drivers: The engine computer is designed with electrical drivers which act like switches inside the computer's circuit board. When one of these drivers goes bad the engine will misfire or stall out completely, this is can be checked by testing the output voltage of these circuits to confirm the failure in which case the engine computer will need to be replaced.

3. Multiple Codes: When there is an error or glitch in the computer firmware it can trigger several codes at once, one of the more popular occurrences of this problem is to get codes for all four oxygen sensors at once on a v8 engine. Since it is virtual impossible for all oxygen sensors to go bad at once, the computer is to blame.

4. Dead Computer: If the computer power and grounds sources have been confirmed and are working correctly included the data port connector, the computer has died. This can happen due to vibration or an electrical surges caused by the alternator, battery or starter. Rain and humidity will also take it's toll on these items.

5. Reduced Fuel Efficiency: Inside the engine computer is a mapping program which tracks various sensors to optimize the fuel delivery and ignition timing. When these maps fail to update or stop optimizing the fuel mileage will suffer, often without a code.

6. Failed 5 Volt Reference: On the sensor side of the engine computer, a 5 volt circuit is used to provide power to the various sensors within the computer network. This 5 volt network system is unique to the engine computer which provides this lower voltage via an internal transformer which can fail rendering the computer no good.

Conclusion

The ECM is a critical component in modern automotive systems, and a failing ECM can cause a range of issues that impact the overall drivability of the vehicle. If you notice any of these symptoms, it’s essential to perform a thorough diagnosis or consult a professional mechanic to confirm the cause.

Credits

This guide knowledge base was created by the 2CarPros Team, and by Ken Lavacot: Automobile repair shop owner and certified master automobile technician of over 30 years. If you have question or need help please ask one of our experts we are happy to help. Please visit our 2CarPros YouTube Channel for additional car repairs.