Engine Control Module Buyer’s Guide
- The engine control module (ECM), also known as the engine control unit (ECU), monitors a vast network of sensors and actuators in your vehicle’s engine bay.
- Depending on your car, your engine control module might have other functions, including idle speed control, electronic valve control, and variable valve timing (VVT) control.
- Generally, the ECM is located on the passenger’s side behind the glove box, under the floorboard or the seats. It could also be located behind the kick panels, under the hood, or below the dashboard.
- When your engine control module malfunctions, your engine’s performance can drop dramatically and cause all sorts of electrical problems.
- The engine control module is an expensive component, so it’s important to conduct extensive diagnostics first before repairing or replacing it.
- Your replacement ECM must match the Service ID and manufacturer-specific ID on the original part.
Your car’s engine is a very complex piece of machinery. Because the engine plays a pivotal role in running your car, it needs something to monitor its efficiency and ensure optimum performance. This is where the engine control module comes into play.
What does the engine control module do?
The engine control module (ECM), also known as the engine control unit (ECU), monitors a vast network of sensors and actuators in your vehicle’s engine bay. These include:
- Engine Coolant Temperature (ECT) Sensor
- Barometric Sensor
- Intake Air Temperature (IAT) Sensor
- Idle Air Control Valve (IACV)
- Throttle Position Sensor (TPS)
- Oxygen Sensor
- Camshaft and Crankshaft Sensor
- And more depending on your vehicle
The data from these sensors is interpreted by the ECM to check if your engine is working normally. If something goes wrong, the ECM makes changes to the air, fuel, and spark ratio to bring everything back within the normal operating range.
Depending on your car, your engine control module may have other functions aside from controlling air, fuel, and spark ratio. These functions can include idle speed control, electronic valve control, and variable valve timing (VVT) control.
Newer engine control modules have embedded memory systems to store important data. This can help your mechanic diagnose the problem when your ECM activates the check engine light signal.
Location of the Engine Control Module
Generally, the ECM is located near your car’s engine. Usually, it is on the passenger’s side behind the glove box, under the floorboard, or under the seats. It can also be located behind the kick panels, under the hood, or beneath the dashboard.
Like many internal car components, however, the location of the engine control module varies depending on your vehicle’s make, model, and year. Your owner’s manual should tell you exactly where the ECM is located.
What are the symptoms of a bad engine control module?
When your engine control module malfunctions, your engine’s performance can drop dramatically and cause all sorts of electrical problems. This means that it’s important to diagnose and repair or replace a bad ECM as quickly as possible.
So how do you know when your engine control module needs to be replaced? Here are some common symptoms of a faulty ECM.
On or flashing engine light
When your ECM detects a major issue, it illuminates the check engine light on your dashboard. Sometimes, the ECM lights up the check engine light by mistake, but it’s still advisable to have your mechanic look at the problem.
Alternatively, you can get an OBD2 scanner so you can check the trouble codes at home. Take note that OBD2 scanners aren’t 100% accurate, so it’s still advisable to get a professional’s opinion if the check engine light remains activated.
An illuminated check engine light signifies ECM trouble, while a flashing one means that the issue is urgent and that it’s happening now. The light flashes every time the ECM detects the issue. So seek expert assistance as soon as possible if the check engine light is flashing intermittently.
Usually, an illuminated or flashing check engine light means that there are issues with your car’s engine or sensors, but it can also mean that your ECM is malfunctioning.
Difficulty in starting your car
If you’re having trouble starting your car or if your car won’t start at all, you might have a bad ECM. Without proper engine management from your ECM, your vehicle won’t be able to run at all.
Stalling or misfiring engine
If you notice that your car has been stalling or misfiring intermittently, your ECM might be the culprit. The trouble with this is that engine problems can be caused by a wide number of things, and there’s usually no pattern to indicate that the issues are caused by the ECM. One thing that can help with this is getting an OBD2 scanner to check the error codes that your ECM is showing.
Poor engine performance
Since the ECM is basically responsible for your engine’s health, it only follows that a bad ECM can have a big impact on the engine’s performance. Rough idle and trouble with acceleration are two big indicators of poor engine performance. An engine that shuts off for no apparent reason is also a sign of poor air-fuel ratio caused by a bad engine control module.
Increased fuel consumption
A bad ECM can impact the way your car uses fuel. A failing ECM will have difficulties managing the fuel-air ratio, causing your engine to burn more fuel than necessary. If you notice that your car’s fuel consumption has increased, you might want to check if your ECM is still in good condition.
The engine control module is an expensive component, so it’s important to conduct extensive diagnostics before repairing or replacing it. Bring your car to your mechanic and have them look at the trouble codes to determine if the ECM is really the root cause of your vehicle’s engine or electrical failures.
Choosing an engine control module replacement
When choosing an engine control module replacement, you really only have to worry about buying an ECM that’s a perfect match for your vehicle. ECMs are basic car parts, so you don’t need to worry about types of materials used and other features. As long as you buy from a reliable OE car parts manufacturer or seller, you won’t be having any issues with choosing your OE ECM replacement unit.
The important thing to remember is that your replacement ECM must match the Service ID on the original part. Another important number is the manufacturer-specific ID. Knowing these two details will help you ensure that you’re getting the correct ECM replacement part.
How much does a replacement engine control module cost?
The replacement of an engine control module can be a pricey fix. An OE ECM replacement part can cost about $45 for a basic ECM that is remanufactured or needs programming. Take note that diagnosing which part of the ECM is faulty is very tricky, and you might end up replacing more parts than you originally intended. Complete engine control module replacement kits can cost up to $2100.
Car Brains with an Engine Control Module
Car Brains with an Engine Control Module
When buying a new engine control module (ECM), it is important to understand what it exactly does. As the "brain" of the car, it analyzes information to automatically manage and control engine performance. This information comes from different sensors that send data to the ECM.
- Air/Fuel Ratio: An ECM measures the air and fuel mixture inside an engine cylinder during combustion. Depending on various factors such (gas pedal pressure, engine temperature, etc.), it automatically injects the right amount of fuel that will give enough power.
- Ignition Timing: In cases where the spark plugs ignite earlier or later during the compression stroke, the ECM automatically corrects the timing and sequencing right. This is done to avoid knocking which can badly hurt the engine.
- Idle Speed: During idling, when the engine is least needed, the ECM adjusts the power output so that fuel is not wasted.
- Valve Timing: For engines with variable valve timing, the ECM adjusts the opening of these valves to allow the right amount of air in depending on the car's speed.
With the many capabilities of an ECM, its accuracy can greatly affect the engine. While a stock ECM does those tasks well, an upgraded one does better in improving engine performance. Some aftermarket units are pre-programmed to fit certain models to bring out the best performance from its engine.
Programmable ECMs are for serious tuners, or those with highly tuned car. Using a spreadsheet program, a tuner can put more accurate engine settings to maximize the engine's potential. Some of the many areas programmable ECMs can control are the following: RPM limit, water temperature, gear control, transient fueling. It is advisable to buy this for a more customized, personalized setup for your car.
Make sure to buy only from a trusted and proven brand to ensure the quality of your purchase. Your car's engine is too valuable to risk being controlled by a faulty computer.
Replacing the Engine Control Module
A car's engine control module (ECM) is a computer system that acts as the "brain" of a car. This little computer analyzes lots of information in order to control the car's performance. When the ECM fails, it will greatly hurt the engine's performance. At its worst, a bad ECM may even result to a car not starting.
Here is a simple guide to help you replace a broken ECM.
Difficulty Level: Easy
- Wrench set
- Socket Set
- Replacement ECM
Step 1: Before beginning, make sure that the car is turned off. Remove the battery cables with a socket wrench. Don't forget to ground yourself afterwards to avoid damaging the computer chip.
Step 2: Locate the car's ECM. The location differs from model to model. It can be placed in the engine compartment, passenger floorboard, under the seats, or behind the kick panels. Refer to your car owner's manual for guidance.
Step 3: Remove all the bolts and brackets that hold the ECM in place.
Step 4: Slightly pull the ECM out just enough to disconnect all the plugs behind it. Make sure that the plugs' ends do not bend. Once free, completely pull out the ECM.
Step 5: For cars that have a PROM (Programmable Read Only Memory) chip, remove the PROM from the old ECM and simply insert it to the PROM slot of the replacement ECM.
Step 6: Reconnect all the plugs to the new ECM and place the unit back to its place. Return all the holdings and brackets to secure the ECM.
Step 7: Start the car and let it idle for about 5 minutes. If there are any problems, the "Check Engine" indicator will light up.
ECM replacement can be done in 30 minutes.