Common Symptoms of a Cummins ECM Failure


Over 5,500 Cummins engines were recalled by the manufacturers in 2016 due to a short circuit in the Engine Control Module. This short circuit led to a blown fuse, which resulted in the engine stalling.

If you are facing issues with your Cummins engine, it is very possible that the ECM has developed a fault. But the problem is, most times, you may not know if the Engine Control Module is faulty.

However, that's about to change.

If you are not sure if the problem is from the Cummins ECM, keep reading. You will know the symptoms to look out for when you have an ECM failure.

What Is an ECM?

The ECM is the engine control module. It is also known as the engine control unit, ECU. It is referred to as the brain of the engine management system. It is responsible for controlling the ignition timing, fuel mixture, variable cam timing, and emissions control.

This device monitors emissions performance constantly through the Onboard Diagnostics (OBD) programming. The ECM also oversees the operation of the engine cooling fan, charging system, and the fuel pump.

Additionally, the engine control module interacts with the stability control system, transmission controller, climate control module, body control module, and anti-theft system.

How does it do all this?

The engine control module controls series of actuators present on the internal combustion engine to ensure the engine performance is at its best. It does this by reading values from so many sensors in the engine bay.

It then interprets data with the lookup tables or multidimensional performance maps and adjusts the engine actuators.

How Does The ECM Work?

Before you are able to diagnose a faulty ECM, you need to know the jobs it's supposed to do. Here's a list of them.

Controls the Air-Fuel Ratio

The engine control module determines the amount of fuel that needs to be injected based on a number of sensor readings.

The ECM is notified by oxygen sensors if the engine is running lean (little fuel and too much oxygen) or rich (so much fuel and less oxygen).

The throttle position sensors are responsible for telling the ECU how open the throttle plate is when the accelerator is pressed.

The engine coolant temperature sensor, on the other hand, helps measure the temperature of the engine. This sensor helps the ECM determine if more fuel will be injected or not.

Controls Idle Speed

The idle speed control is in the engine control module. The engine revolution per minute is monitored by the crankshaft position sensor. This plays a role in the engine timing functions for spark events, valve timing, and fuel injection.

The idle speed is controlled by a throttle stop that is programmable. This gives cruise control functions and limitation of top speed. It also monitors the ECM for reliability.

Variable Valve Timing Control

The ECM controls the time in the engine cycle when the valves open. The valves usually open early when the speed is high and late when the speed is low.

This helps increase air flow into the cylinder thereby increasing fuel and power economy.

Electronic Valve Control

The ECM operates the hydraulic pumps that open the valves. The valves can open so many times per stroke intake based on engine load.

The ECU decides the amount of fuel that should be injected in order to optimize combustion. When conditions are right the valve opens, fuel is injected, and the valve closes.

If there is a sudden increase in throttle, the valve opens up in the same stroke intake and a greater amount of fuel is injected. This permits immediate acceleration.

For the next stroke, the engine control module calculates the engine load at the new higher revolution per minute and decides to open the valve late or early, half-open or wide-open.

Common Reasons for Failure in Cummins ECM

If your ECM fails, or you suspect it has failed, these are the common areas you should have a look at.

The Fuel Solenoid

The electronic fuel solenoid is the valve via which fuel passes through. It is located at the top of the fuel pump.

This part could be one of the reasons for an ECM failure.

This is because the solenoid is capable of causing a short in the ECM due to corrosion in the wires that run from the solenoid to the ECM harness.

If you realize your truck runs fine until you shut your engine off and it refuses to restart, this could be an indication that the ECM has been short out by the fuel solenoid.

Moisture and Corrosion

Damage as a result of moisture or corrosion is one of the reasons for ECM failure. As a matter of fact, it should not be overlooked.

This is because moisture can enter as a result of a failure in the seals of the ECM itself. With the entry of moisture, corrosion is bound to occur especially at the wiring.

This does not happen in a day. It happens over a period of 5 to 10 years due to the ECM's exposure to the elements.

Dead Cell Batteries

There are cases where batteries are left in the rig long after a cell has died. This affects the grounding in the battery. These dead cells can result in the failure of the ECM.


When you replace your starters with a wrong one, it could be the beginning of a new and big problem with the ECM.


So many starter rebuilders usually bypass the override sensor in the starter.

The override sensor is responsible for regulating the voltage that goes to the ECM. In a situation where the override sensor is bypassed, voltage problems in the ECM will develop.

This voltage can cause generation of faulty codes or other problems. In this scenario, you can only assume that the starter is the root cause of ECM failure if the problem starts after installing a new one.

Sensor Wiring Harness

One of the things that can result in ECM failure is the sensor wiring harness.

When there is a break in the internal wiring in the harness or corrosion, a short develops.

Grounding Issues

One of the problems that result in the failure of the ECM is grounding issues. This occurs when there is corroded or lose ground wires connected to the battery or the frame of the battery.

Lightning and Welding

When lightning strikes the ECM, it can fry off. Also, when an arc welding is done on the frame of the ECM, it can result in a failure of the ECM.

This is a rare case.

Jump Start

If you jump-started your car and the cables that were connected to carry out the procedure were not done well, a spike can be induced in the ECM.

A bad jump start can also blow out 2 fuses located between the firewall and ECM. This contributes a lot to the failure of the ECM.

Symptoms of ECM Failure

How would you know your ECM is failing?

Here are the common Symptoms of a Cummins ECU failure you should watch out for.

Engine Misfiring and Stalling

If your Cummins engine starts stalling or misfiring, then this might be an indication of a faulty ECM. This is because the engine firing and timing is controlled by the ECM. Thus such erratic behavior may be a sign of a fault.

Issues with the Engine Performance

If your engine starts developing some performance issues, then this may be a sign of ECM failure.


The fuel and time settings are usually thrown off at this stage. This affects the engine performance negatively.

Most times, the truck experiences a drastic reduction in its power, acceleration, and an increase in fuel consumption.

The Cummins Engine Won't Start

In cases where the Cummins truck clearly refuses to start or run, it may mean that the ECM has completely failed.


The engine will not be able to start without the vital inputs from the computer. This is despite it cranking.

They are so many issues that can lead to this symptom. It's thus best that you get a professional to check it out for you.

Check Engine Light Comes on Frequently

Seeing the "Check Engine Light" often on the vehicle dashboard is one possible symptom of an ECM failure.

The "Check Engine Light" frequently comes on when the vehicle system detects an issue with any of its circuits or sensors.

However, there are situations, where the ECM shows a "Check Engine Light" when there is no problem. Diagnosing the vehicle with a scanner for trouble codes can show if the problem is coming from the ECM or any part of the vehicle.

Your Cummins Truck Runs Well Only When Hot or Cold

If you discover that your Cummins truck accelerates fine when it is very cold or hot, try replacing the cam sensor first. If it persists, try wiping the ECM connectors clean.

If it still proves abortive, it is a bad symptom. This means your ECM is about to fail.

You have to replace your ECM at this point. Yet, most times, this failure may be as a result of corrosion and wiring issues.

Your ECM Has Aged

In the long run, even the best-built Cummins ECM will fail as result of old age. There will be cases where your EP lights don't cycle and your engine doesn't start when you turn your key ignition.

If you tend to see this often, then you are observing the last days of your Engine Control Module's lifespan. It's time to buy a new one.

Experiencing Some Sort of Friction During Transmission

If you experience any form of friction when shifting gears during your transmission, it easy to conclude that the transmission has issues.

Hence, you try servicing the vehicle transmission but the issue persists. However, in some cases, the ECM failure could lead to this sign. This is especially the case where the ECM is also responsible for managing the car's transmission.

Water Damage or Fire Damage on the ECU

If you are having suspicions about your ECU, this is one way to confirm if it is in a good state or not. Open your ECU cover case and look for any form of fire damage or water damage on the panel.

If you see fire damage on the circuit or some form of corrosion caused by water, then your ECU needs to be replaced.

Overheating ECU

This is a symptom that can be noticed when the ECU is removed from its seating in the engine. If your ECU undergoes any form of overheating while you are driving, it is a clear sign that it's about to fail.

ECU Has Broken Pins

In addition to the overheating, broken pins can act as a confirmation of ECM failure.

What to Do If Your ECM Fails

Since the ECM plays such an important role in the working performance of your vehicle, any problem that arises can be fatal to the engine. Thus, the Cummins trucks produced these days are highly computerized, sophisticated, and complex.

This is in an effort to ensure the ECM is robust.

Thus, diagnosing and troubleshooting these ECM has become more difficult.

For this reason, if you have any suspicions about your ECM, it is better you leave it to experienced professionals. Detecting the problem early can save you a lot of time and money.

What about the costs?

Replacing a faulty ECM can be expensive. Nevertheless, it can be reprogrammed or fixed in some cases. This can help you save the expense of replacing the entire part.

It is vital to note that most of these symptoms of ECM failure can be signs of other system failures or even problems with your Cummins truck.

Bottom Line

If you desire a high-performance vehicle all the time, then you have to invest in your Cummins ECM. Remember, it is the brain behind the engine management that makes your vehicle obey your every command.

If you need more information about this subject, contact us today.

Posted On: 31/05/2018

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