How To Identify And Fix Faulty Cummins Engine Sensors

With their unmatched performance and unwavering commitment to quality manufacturing, Cummins has earned a reputation as one of the finest heavy-duty engine manufacturers on the planet. But that doesn’t mean they don’t experience issues. 

Modern engines come equipped with an array of electronic systems that provide real-time information to the driver and instructions to the engine to perform certain functions. Like all other components, these electrical systems can suffer from a range of problems. On this page, you will find everything you need to identify and fix faulty Cummins engine sensors. 

Overview of Cummins Sensors 

Cummins engines come jam-packed with a variety of different sensors, each to monitor different component aspects. Some of these include: 

Mass Airflow Sensor (MAF): MAF sensors measure the amount of air entering the engine, which helps the ECM calculate the appropriate amount of fuel to inject to optimize combustion. 

Throttle Position Sensor (TPS): Monitors the throttle valve and provides feedback to the ECU, which then adjusts the fuel delivery and throttle response accordingly. 

Coolant Temperature Sensor (TPS): TPS monitors engine coolant temperature and helps the ECU determine the correct fuel mixture and ignition timing based on the engine’s temperature. 

Oxygen Sensor (02): These measure the oxygen content in the exhaust gases and provide feedback to the ECM, allowing it to adjust the air-fuel mixture for optimal combustion efficiency and emission control. 

Crankshaft Position Sensor (CKP): By monitoring the position and rotational speed of the crankshaft, it allows for proper fuel injection timing, ignition timing, and synchronization with other engine components. 

Camshaft Position Sensor (CMP): This sensor detects the position and speed of the camshaft and helps synchronize the opening and closing of the engine’s valve.

Knock Sensor: Detects abnormal vibrations or knocking noises within the engine. It alerts the ECU, which then adjusts the ignition timing to prevent engine damage caused by detonation. 

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Common Symptoms of a Faulty Sensor 

There are a few ways to identify faulty sensors in your heavy-duty truck. These include: 

Warning lights on the dashboard: Your ECM will flash up different lights that correspond to different malfunctions on your dashboard. Ones to look out for include specific sensor lights and the check engine light. 

Decreased engine performance: Sluggish acceleration, reduced power output, and poor fuel efficiency could be indicators of sensor problems, especially if there are no apparent mechanical issues. 

Irregular engine idling: Faulty sensors can disrupt your engine’s idle control system, causing irregular idling or stalling. This may cause the revs to be too high or too low and exhibit rough idling or unexpected stalling. 

Unusual noises or vibrations: Your truck makes a lot of noise as it is, so this one may be a bit difficult to pinpoint, so be on the lookout for excessive vibrations and knocking noises caused by improper combustion. 

Enhanced emissions: These sensors are used to control the EGR and DPF aftertreatment systems. If they fail, your vehicle could violate EPA regulations that come with hefty fines. 

If you notice any of these in your Cummins engine, it requires immediate attention from professional engine repair services like our team at National Fleet Management. Failure to act on these could lead to these issues causing further damage to your engine, including catastrophic explosions on the road.

Identifying Sensor Issues  

Diagnostic Tools Process

Diagnostic tools are advanced pieces of hardware that interpret data from the engine’s sensors and locate which sensor is showing signs of failure. 

1. Connect the diagnostic tool

Connect it to the vehicle’s OBD-II (On Board Diagnostics) port, which can typically be found below the dashboard. Make sure you follow the manufacturer’s instructions to connect properly. 

2. Scan for trouble codes 

Trouble codes provide specific information about the nature of the sensor malfunction and are displayed on a screen. 

3. Interpret the trouble codes 

Using the diagnostic tools manual or an online database, these codes can be interpreted to locate the specific sensor malfunction.

Visual Inspections 

Sometimes cutting-edge technology isn’t needed to solve sensor issues; a quick look inside can help quickly identify what is causing the problem.

1. Inspect sensor connections

Carefully examine the connections between the sensors and wiring harnesses. 

2. Checking for damaged wiring 

Inspect the wiring leading to the sensors for any visible damage. Things like frays, cuts, and exposed wires can all cause erratic sensor readings or complete sensor failure. 

3. Signs of moisture and corrosion 

These are large factors that can impact sensor performance. Checking for signs of water intrusion or corrosion around the sensor connections. 

Fixing Faulty Cummins Engine Sensors 

Now that you’ve identified the issue, it’s time to get to work and resolve it. 

Replacing a Faulty Sensor 

1. Gathering the correct tools 

These can include wrenches, sockets, pliers, and diagnostic tools. Make sure you refer to the vehicle's manual to check what you need. 

2. Locate the sensor within the engine 

If you’re unsure, this can be found within the vehicle’s manual or online. 

3. Disconnect the old sensor 

1. Ensure that the engine is off and cooled before you begin. 
2. Locate the electrical connector attached to the sensor. 
3. Carefully detach the connector by pressing any release buttons or gently pulling it apart.
4. If the sensor is threaded, use an appropriate wrench or socket to loosen and remove it from its mounting. 

4. Install the new sensor 

1. Make sure the sensor is compatible by comparing it with the old one.
2. Apply any recommended sealant or thread-locking compound to the sensor, if applicable. 
3. Thread the new sensor into its mounted location by hand to avoid cross-threading. 
4. Use a wrench or socket to tighten the sensor securely, following the manufacturer's guidelines. 
5. Reattach the electrical connector by aligning the tabs and pushing it until it clicks into place.

5. Test the sensor

Before patting yourself on the back for a job well done, it is important to test the sensor for functionality. Start the engine and check the warning lights or any normal behavior. Use the sensor to provide accurate readings. 

Final Thoughts

Now that you know just how complex Cummins engine systems are, you’re ready to go and diagnose and resolve these issues yourself. Although, without the correct training and equipment, this may be an issue. 

Luckily, that’s where we come in. Just pay a visit to us at National Fleet Management, and our skilled mechanics will promptly diagnose and resolve any issues your heavy-duty truck may be experiencing and get you back on the road in no time.