Reference Mark Transmitter Check

924 & 944 Models
1. Turn ignition Off, then remove DME ECU multiple wiring connector.
2. Connect suitable oscilloscope to terminals 25 and 26 of ECU connector.
3. Start engine, then observe oscilloscope tube. A single sine wave should be displayed. The oscillation should begin with a positive slope displaying at least 2 volts with a starter speed of at least 200 RPM. As engine speed increases, the display amplitude should also increase.
4. If transmitter output is less than 2 volts, check clearance between reference mark transmitter and ring gear. Refer to System Service for procedure.
5. If display shows no transmitter signal, proceed to step 6.
6. Using suitable ohmmeter, measure between ECU connector terminals 25 and 26 to determine reference mark transmitter coil resistance. Resistance should be .6 - 1600 ohms.
7. If resistance is not within specifications, replace transmitter.