Engine Speed Sensor Check
The sensor is driven by the camshaft. A 5-volt reference signal is provided by the ECM. The ECM measures engine RPM by counting the number of voltage pulses created by the speed sensor (about 4 times per revolution).
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- This step ensures a good 5-volt reference signal. Normally, the ECM should be at about 5 volts for fully charged batteries.
- This step checks for proper ECM voltage to the speed sensor. If circuit to ECM is complete, normal voltage should be about 5 volts with harness disconnected at speed sensor.
- This checks for good sensor ground circuit (452) from sensor to ECM. Because step 2) indicated an open circuit, this step indicates whether the open is in the wire or at the ECM.