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> Engine Control Modules

Engine Control Modules

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As fuel delivery systems transitioned from carburetion to fuel injection, the engine control module or ECM became one of the most vital components on any vehicle. Responsible for interpreting data from numerous engine sensors to optimize fuel economy and power, this module also plays a big part in aftermarket modifications for increased horsepower and torque.  Understanding how the ECM works and the ways it can be modified or tuned is an important step in improving the power created by your engine.

Image of an engine control module (ECM)
An engine control module (ECM) sometimes referred to as a computer.
First, some clarification: sometimes the terms “performance chip” and “ECM” are used interchangeably. This is inaccurate and can lead to confusion during the shopping process. The difference is specified below.
  • ECM: The computer tasked with managing the operation of your vehicle’s engine. Nearly every vehicle manufactured since the early 90s is equipped with some form of an ECM.
  • Performance Chip: An aftermarket computer chip that can be added to certain ECMs to alter their performance parameters, thereby increasing horsepower and torque.



Image of a Diablosport tuner
A tuner from Diablosport. This can be used to alter the operating parameters of an ECM.

How Engine Control Modules Work

Modern engines are equipped with a number of sensors which record engine information on parameters ranging from the position of the crankshaft and camshaft, to coolant temperature and incoming air density. The data gathered by these sensors is relayed to the ECM. This information is then interpreted by the ECM to determine how much fuel should be added to the air/fuel mixture, providing optimum performance.



Image of a Hypertech performance PROM chip
A Hypertech performance PROM chip which replaces the stock PROM in an ECM.

Modifying Engine Control Modules

Since the ECM plays such an important role in governing engine performance, altering the parameters of the module is one of the most common methods of increasing torque and horsepower. On most older computer-controlled vehicles and a few newer ones, a performance chip replaces the existing chip within the ECM to create more power. On newer vehicles equipped with OBDII diagnostic ports, a device called a programmer or tuner is used to recalibrate the ECM. Programmers are extremely versatile and can be used to do everything from reading diagnostic trouble codes to making speedometer corrects for oversized tires. To learn more about chip tuning, performance chips, and programmers, check out our Performance Programmer Research Guide.