A car's engine uses multiple sensors for communicating essential information to the vehicle's on-board computer. Two particular detectors are the crankshaft and cam sensors. The crankshaft sensor reports the position of the crankshaft, whereas the cam sensor communicates the cam's position within the engine. This information from both sensors tells the computer how fast the engine is running in RPMs and when the engine's valves are open or closed. However, a malfunctioning engine may require a check of both the crankshaft and cam sensors. Simple sensor troubleshooting techniques can help alleviate engine problems.
Verify the sensor type by observing its outside assembly. A magnet should be visible on the sensor's exterior. The sensors can be either a magnetic or Hall effect type, requiring different testing methods. However, both the crankshaft and cam sensors test in the same manner.
Verify the resistance of the sensor's terminals. Disconnect the electrical connectors from the terminals. Place the multimeter's leads, set for resistance measurement, across the two terminals. Each vehicle manufacturer uses different resistance values for the sensors, such as between 500 and 900 ohms. The multimeter should reflect a similar value. The sensor has failed if the multimeter reflects an open or shorted circuit.
Replace the sensor if it has failed. Typically, both the crankshaft and cam sensors cannot be repaired.
Place the multimeter's leads, set for voltage measurement, across the positive and negative terminals of the Hall effect sensor. Allow the vehicle to idle during testing. Hall effect crankshaft and cam sensors use switches for determining engine timing.
Observe the voltage value on the multimeter. As the vehicle idles, the voltmeter should move significantly up and down in voltage value as the Hall effect switch reacts to the crankshaft and cam's positioning. The sensor has failed, requiring replacement, if the voltmeter does not reflect any voltage or does not move significantly during testing.
