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How to check if Camshaft Position Sensor is bad

How to check if Camshaft Position Sensor is bad

A camshaft position sensor is an electronic device designed to monitor the camshaft speed and position in the car engine.

While performing these exercises, the device can send the information to the Engine Control Module (ECM).

The Engine Control Module requires this information to control the oxygen and fuel ratio that enters the combustion chamber.

Additionally, the ECM determines the ignition and fuel injection timings depending on the power needed hence the need to know how to check if camshaft position sensor is bad thus respond promptly.

Image: Crankshaft

The camshaft position sensor is crucial in modern cars with auto-start and auto-stop engines.

It checks which cylinder is in the power stroke related to the crankshaft’s position if the idle engine has switched off.

Afterward, it will signal the ECM if the driver accelerates to deliver fuel and spark to start the engine.

How to check if Camshaft Position Sensor is bad; Understand Symptoms

Image: Motorcycle camshaft

Before checking if the camshaft position sensor is bad, it’s good to observe the below symptoms keenly. They may assure you of a faulty camshaft sensor before taking action.

Poor vehicle performanceIt idles roughly, slow acceleration, jerking and surging forward, ignition problems.
Check Engine Light illuminatesThe check engine alert appears on the dashboard.
Transmission Shifting ProblemsThe ECM activates Limb Mode in transmission lowering the car’s speed.
Poor Fuel MileageExcessive fuel is injected into the combustion chamber, leading to higher emissions.
Engine StallingFuel and spark delivery switches off.

Related: Engine overheated but still runs

1. Poor Vehicle Performance

If the camshaft position sensor is bad, you’ll notice a drop in engine power, slow acceleration, jerking, and vehicle surging forward while driving.

Additionally, you’ll note rough idling when parked and ignition problems at some point.

Due to less signal received by the ECM, the engine combustion chambers receive an imbalanced fuel-oxygen ratio and improper ignition timing leading to the above symptoms.

Image: Engine camshafts

2. Check Engine Light Illuminates

When the ECM fails to receive the signal from the camshaft position sensor, it will illuminate the check engine light.

However, the check engine light may indicate various problems within the engine. You’ll have to take your car for scanning to confirm which part of the engine is faulty.

Related Read: Timing belt replacement gone wrong

3. Transmission Shifting Problem

Lack of enough signal from the camshaft causes the ECU to activate Limb Mode in the transmission system. It’s a state where the transmission is locked, and gears cannot shift.

The Limb mode helps protect the engine from extreme damages by lowering its performance.

4. Poor Fuel Mileage

A bad camshaft position sensor will deliver wrong information leading to excess fuel injection to the combustion chambers. As a result, it causes the emission of unburned fuel through the tailpipe.

In this case, you may hear the engine misfire due to an untimed spark and the gas smell from the tailpipe.

5. Engine Stalling

Fuel and spark delivery signals weaken as the signal reaching the ECM from the camshaft weakens.

Afterward, if the sensor completely fails, the engine may stall at parking or while driving, which may be dangerous.

Read: 2 stroke power valve adjustment

Image: Motorcycle camshaft

How Do You Test a Camshaft Position Sensor?

After confirming your camshaft position sensor has an error, it’s good to unplug the sensor connector and check if there is rust or oil causing failure.

However, to check if the sensor is bad, you may use a digital multimeter (DMM) capable of testing both alternate current-voltage (AC) and direct current-voltage (DC).

Depending on the type of your sensor, this article will cover the procedures of checking the two common types of sensors;

a) Two-Wire Sensor Testing

When testing a two-wire magnetic type sensor, set the Digital multi-Meter to AC volts. First, test if the circuit is complete;

  • Turn the ignition key on but don’t start the engine.
    • Touch the ground wire with one of the DMM tool probes and touch each of the remaining wires with the other probe.
    • If neither has the current, know that the sensor circuit is bad.

The second step is to test the sensor signal as follows;

  • Start the engine
    • Touch your DMM probes to both sensor wires
    • If the meter displays information, refer to your repair manual to confirm your sensor’s condition.
    • If no signal is displayed, the sensor is bad.

b) Three-Wire Sensor Testing

The first step is to test the circuit as follows;

  • Identify the ground, power, and signal wires by referring to the car repair manual.
    • Set your DMM tool to direct current (DC)
    • Turn the car ignition on but don’t start the engine.
    • Touch the black probe of your meter to the ground wire and the red to the power wire.
    • Compare your readings with the vehicle repair manual specifications.

The second step is to test the sensor signal. Carry out this procedure;

  • Start the car engine
    • Touch the ground wire with the black probe and the signal wire with the red probe.
    • Compare the reading displayed with your car repair manual specifications.
    • If the signal is lower than specified or no signal at all, the sensor is bad

NB: Worn out timing belt can make the camshaft position sensor send inappropriate information to the ECM.

Image: camshaft

Can You Clean Camshaft Sensors?

Cleaning the camshaft position sensor will save you the replacement cost. Here is the safest procedure to follow;

1st: Disconnect the car battery negative terminal cable.

2nd: Refer to your car’s repair manual to locate the camshaft location sensor.

3rd: Note the functions of the three wires of the camshaft sensor as you detach them.

4th: Remove the screws that hold the sensor to the distributor, then pry it out using your screwdriver.

5th: Spray a small amount of solvent cleaner on the sensor and dry it.

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6th: Replace your sensor, attach the three wires to their positions, and connect the battery’s negative terminal cable.

What can cause a camshaft sensor to go bad?

Many circumstances may cause a camshaft position sensor to fail. They may be;

  • The normal wear-and-tear
  • Corrosion damage
  • Water damage
  • A damaged cylinder head gasket can cause an oil leakage to the sensor.

Checking if the camshaft position sensor is bad and maintenance is a simple practice.

With the knowledge of the above-discussed symptoms and maintenance processes, you’ll have assurance of all that your car requires before taking any action.

Read: How to check for vacuum leaks on carburetor

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