How can you diagnose a faulty camshaft position sensor?

A camshaft position sensor (CPS) is a device that monitors the rotational speed and position of the camshaft, which controls the opening and closing of the valves in the engine. A faulty CPS can cause various problems, such as poor performance, stalling, misfiring, or a check engine light. In this article, you will learn how to diagnose a faulty CPS using some common tools and methods.

1 Symptoms of a bad CPS

If you notice any of the common symptoms of a faulty CPS, such as rough idling or hard starting, reduced power or acceleration, engine hesitation or surging, engine cutting out or stalling, a check engine light on or flashing, or trouble codes related to the CPS or the camshaft timing, you should check the CPS as soon as possible to avoid further damage to the engine. Identifying these symptoms is the first step to diagnose a faulty CPS.

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Presanna Govindaraj
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Diagnosing a faulty camshaft position sensor involves several steps. Begin by checking for common symptoms such as engine misfires, rough idling, or difficulty starting the vehicle, which may indicate sensor malfunction. Utilize an OBD-II scanner to retrieve diagnostic trouble codes (DTCs) related to the camshaft position sensor. Inspect the sensor for physical damage or corrosion, and test its electrical connections for proper voltage and continuity. Additionally, perform a resistance or voltage test on the sensor to verify its functionality according to manufacturer specifications. Finally, if necessary, replace the sensor and clear any stored fault codes to restore proper engine performance.

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Khant Min Lwin

Service Engineer (Caterpillar Energy & Transportation Industry)
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One of my customers said his engine have been so difficult to start in sometimes but not always. Also, the engine have abnormal noise and a little vibration. In worst case, engine has been shutdown while running with load.

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martin mulvihill

maintenance project at John Crane
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In my experience while engine is running idle at 750/800 rpm you will see and hear rpm hunting up and down CPS is not giving correct pickup sensing also while driving in 4th gear you will find lost of power in engine performance

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2 Location and inspection of the CPS

The next step is to locate and inspect the CPS for any visible signs of damage or wear. The CPS is usually mounted on the cylinder head, near the camshaft sprocket or pulley, or on the timing cover. You may need to remove some components, such as the air intake, to access the CPS. You should also disconnect the battery before working on the CPS.

Once you locate the CPS, you should inspect it for any cracks, corrosion, dirt, or oil contamination. You should also check the wiring and the connector for any loose, broken, or frayed wires. If you find any obvious defects, you should replace the CPS and clear the trouble codes.

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Khant Min Lwin

Service Engineer (Caterpillar Energy & Transportation Industry)
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If customer ask for intermittent shutdown & hard starting, it always good to start troubleshooting with basic steps like fuel, air, lube, coolant & electrical system. And after that, if we have the leads for bad cps sensors in electrical systems, then we should start identify where is the CPS. In my experiences, most of the CPS is installed on timing cover. And because of the vibration and usage, mostly there is possibility for loose sensors connection. I normally perform wiggle test for this kind of sensors issues.

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3 Testing the CPS with a multimeter

Testing the CPS with a multimeter to measure its resistance and voltage is a good way to determine if it is working properly. Refer to the service manual of your vehicle for the specific values and procedures for your CPS. Generally, you will need to set the multimeter to the ohms or resistance mode and connect the probes to the terminals of the CPS connector. Compare the reading with the specified range in the manual; if it is out of range, then the CPS is faulty. Additionally, set the multimeter to the volts or AC mode and connect the probes to the terminals of the CPS connector. Crank the engine and observe the reading; it should vary according to the speed and position of the camshaft. If it is constant or zero, then it is likely that your CPS is faulty.

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4 Testing the CPS with a scan tool

Another way to test the CPS is to use a scan tool that can display live data from the engine. You will need to connect the scan tool to the diagnostic port of your vehicle and select the CPS data. You should see a waveform that shows the signal from the CPS. You can compare the waveform with a known good one from the manual or online sources. If the waveform is erratic, missing, or different from the expected one, the CPS is faulty.

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5 Replacing the CPS

If you confirm that the CPS is faulty, you will need to replace it with a new one. You will need to follow the reverse steps of removing the old CPS, making sure to align the new CPS properly and tighten the bolts securely. You should also reconnect the battery and clear the trouble codes. After replacing the CPS, you should test the engine and check for any remaining symptoms or codes.

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alexandre platel

cranes maintenance
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Well, This article is not complete. Some engines have cps installed on fly wheel too, And sometimes same physical sensor integrates rpm and cp. Can often be a kind of magnetic pick-up sensor / switch, so can be tested with a simple multimeter.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How can you diagnose a faulty camshaft position sensor?

1

2

3

4

5

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1 Symptoms of a bad CPS

2 Location and inspection of the CPS

3 Testing the CPS with a multimeter

4 Testing the CPS with a scan tool

5 Replacing the CPS

6 Here’s what else to consider

Electronic Engineering

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How can you diagnose a faulty camshaft position sensor?

1

2

3

4

5

6

1 Symptoms of a bad CPS

2 Location and inspection of the CPS

3 Testing the CPS with a multimeter

4 Testing the CPS with a scan tool

5 Replacing the CPS

6 Here’s what else to consider

Electronic Engineering

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