Engine Speed Sensor: Description and Operation

Engine Speed Sensor G28

The engine speed sensor is a Hall style pickup that senses a toothed crankshaft reluctor or magnetic flywheel. The crankshaft reluctor type will have the sensor mounted on the lower portion of the cylinder block. The flywheel trigger style sensor is mounted in the lower front flywheel housing of the transmission case. They both operate on the same Hall effect signal of a square waveform which will vary in length as speed increases. The sensor contains a signal circuit, a 5 volt reference circuit and a ground. A larger tooth or gap between teeth is used to reference the number 1 cylinder. The sensor is used to determine engine speed, individual cylinder knock control, cylinder 1 reference, injector timing and cylinder misfire diagnostics. If the engine speed signal drops out while driving, the engine will continue to run in most current configurations. If the signal is not present during cranking, the engine will not start.