What are the Symptoms of a Failing Mercedes ECM?

First, we should take a quick look at what an ECM is and what it does.  The ECM stands for engine control module.  It is sometimes known as an engine control unit (ECU) or a powertrain control module (PCM).  The ECM essentially functions as the vehicle’s main computer, which controls the engine performance and drivability functions.  The numerous sensors on your car send data to the ECM so that it may calculate and tune the engine.  It is a very important component for proper fuel efficiency and power.  Now, we will take a look at the symptoms of a failing Mercedes ECM.

The Check Engine Light comes on

Although the Check Engine Light can come on for a number of reasons, including problems with the vehicle sensors and circuits.  A primary one is due to the ECM showing erratic behavior or even that it has failed altogether.  The Check Engine Light will indicate a problem in which a certified mechanic or at-home Do-It-Yourselfer can check the engine by scanning for trouble codes.  The proper code will tell the mechanic if it is the ECM.

Vehicle not starting

The engine will still attempt to turn over (crank), but it will be unable to start.  This symptom can be confusing as there are other reasons for it behaving this way.  However, when the ECM fails completely, it will not allow the car to start without the vital inputs from the engine control module.  Before assuming the reason, it is better to diagnose the problem with a computer scan.

Engine misfiring or stalling

When the ECM is starting to have problems the engine will likely display erratic behavior.  As the computer struggles to correctly keep the car in tune it will often cause it to sputter or stall out.  The symptoms may come and go, but will almost always get worse.

General performance issues

Mercedes cars are known for their high performance.  Prior to a complete failure, you may notice that the car is not as fuel efficient as usual.  It may have a reduction in power and acceleration as well.  This would be possibly noticeable on the highway, when needing to pass another car.  Your car would seem to be lacking its usual pep.


Since the ECM is so vital to the performance of the engine, any and all issues with it can cause major problems with the overall functionality of the vehicle.  Today, modern cars are increasingly likely to have several computers onboard, but especially an engine control module.  A mechanic that has the computer device needed to investigate the issue and help determine the cause of the problem is necessary.  The time will come to replace the ECM.

The best place to find good deals and high quality parts is online, where the selection can be enormous.  These online sellers often are the ones who supply the small warehouses and stores where mechanics will source the replacement parts.  Take the time to shop around before making the purchase.

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What are the Symptoms of a Failing Mercedes ECM?

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