What is an Engine Control Module (ECM)?

What is the ECM, and how does it work?

The Engine Control Module (ECM), also called the Engine Control Unit (ECU), ensures that your vehicle operates at optimal performance. The ECM monitors the sensors in the engine bay of your vehicle by managing your vehicle’s fuel mixture and regulating the emission control system. The ECM regulates four main parts of your vehicle’s fuel injection system: air-fuel ratio, idle speed, variable valve timing, and electronic valve control. In terms of the air-fuel ratio, the ECM uses sensors to regulate the oxygen to fuel level detected in your car to detect an engine rich/lean reading. For the idle speed, the ECM relies on sensors located in the crankshaft that track your vehicle’s RPM and engine load while the vehicle is idle. The variable valve timing is in relation to the flow of air into your vehicles cylinder to increase either power or fuel economy. Lastly, the ECM controls the hydraulic pumps which determine the rate of fuel injection that maximize the valve rate of opening per intake stroke to improve engine performance.

When does the ECM need to be replaced?

  • Check Engine Light is illuminated
  • Engine misfires
  • Lower engine performance
  • Car fails to start

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Comments 3

Alfredo Torres

December 18, 2018

Great information..


July 9, 2019

I have an 88 Ford Econoline 150 van it keeps idling High and acts like it wants to stall more at lower speeds and when stopped it seems I had it stall wants and could not get it started had it towed replace the ignition modulator it was running good for a few days then it went back to the high idle and acting like it wants to stall very frustrating I cannot figure out the problem also when it acts like it’s going to stall it does it quickly like it doesn’t slowly glug down it just acts like cut off quickly then picks back up please any advice would help

Bucklin Moon

August 6, 2019

HUGE surprise to have a complicated engine part explained clearly and succinctly. Thank you.

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