How Do You Test A GM Crankshaft Hall Sensor?
The crankshaft sensor on GM vehicles is a hall-effect type with two switches and a single shared magnet. It gets its voltage from the ignition control module (ICM). The module sends the power–12 volts–to the sensor; the sensor gives off a dual set of pulses–a 3X and an 18X–which are returned to the ICM. These pulses are interpreted by the ICM as a crankshaft position in relation to top dead center on the number 1 cylinder. The ICM, after analyzing these signals, adjusts the timing in the ignition and grounds the coil, causing a secondary ignition to the spark plugs. Pull the codes with the code scanner. Plug the scanner into the OBS port under the driver’s side dash. Turn the ignition key on and press the button on the scanner marked “read.” Write the codes down and cross-reference them with the code definition chart that comes with the scanner. If a problem with the crankshaft sensor occurred in the past or is presently occurring, there will be a code stating “crankshaft sensor fa
