Speed Sensor Check

924 & 944 Models
1. Turn ignition Off, then remove DME ECU multiple wiring connector.
2. Connect suitable oscilloscope to terminals 8 and 27 of ECU connector.
3. Turn engine over with starter while observing oscilloscope tube. Sine waves should be displayed with amplitude of 2.5 volts or more from peak to peak.
4. If amplitude is less than 2.5 volts peak to peak, check clearance between speed sensor and ring gear. Refer to System Service for procedure.
5. If clearance between ring gear and speed sensor is satisfactory, or if pattern is not displayed or weak, proceed as follows:
a. Using suitable ohmmeter, measure between ECU connector terminals 8 and 27 to determine speed sensor coil resistance. Resistance should be .6 - 1600 ohms.
b. Using ohmmeter, measure between ECU connector terminals 5 and 8 to determine speed sensor insulation resistance. Resistance should be 1 M-ohm.
c. If resistances are not within specifications, replace sensor.