Code 28
- Turn ignition switch off. Remove speed sensor from transmission. Disconnect speed sensor connector. Connect ohmmeter between terminals for the speed sensor connector. Slowly rotate speed sensor one turn. Ohmmeter should show approximately 8 pulses for every turn of the speed sensor. If ohmmeter reading is okay, go to step 2). If ohmmeter reading is not okay, replace the speed sensor.
- Check the speed sensor circuit. Disconnect speed sensor connector. Connect the positive lead of a voltmeter to the White wire with a orange tracer of the speed sensor connector. Connect the negative lead of the voltmeter to the Black with Blue tracer wire of the speed sensor harness connector. Turn ignition to "RUN" position.
- Voltmeter should read at least 8.5 volts. If voltage is okay, inspect transaxle drive gear to speed sensor drive gear for proper contact. If 0 volts, move voltmeter negative lead to a good engine ground. If voltmeter now reads correct voltage, repair ground wire for an open circuit. If voltmeter still reads 0, go to step 4).
- Check speed sensor wire to computer. Turn ignition switch off. Disconnect the computer 14-wire connector. Connect an ohmmeter between cavity No. 2 of the 14-wire connector and the White with Orange tracer wire of the speed sensor harness connector. If ohmmeter shows continuity, replace computer. If no continuity, repair wire for an open circuit.