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| Illustration 1 | g00764795 |
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(1) Secondary speed-timing sensor
(2) Primary speed-timing sensor | |
If primary speed-timing sensor (2) cannot sense engine speed, the "DIAGNOSTIC" lamp will indicate a diagnostic fault code. The diagnostic fault code will be logged in the memory of the Electronic Control Module.
If primary speed-timing sensor (2) cannot sense engine speed, the automatic default will use secondary speed-timing sensor (1). The secondary speed-timing sensor will be used until the ECM reads a signal from the primary speed-timing sensor that is valid. The engine will shut down if both speed-timing sensors fail. This does not necessarily indicate that the sensor requires replacement.
Failure of the Speed-Timing Sensor
If any of the following conditions are present, a failure of the speed-timing sensor may have occurred:
- The speed-timing sensor output has opened.
- The speed-timing sensor is shorted to ground.
- The speed-timing sensor is shorted to supply.
- The speed-timing sensor is missing pulses.
- The speed-timing sensor has extra pulses.
Intermittent failure causes erratic engine control. The electronic control system will detect a failure of the primary speed-timing sensor. The operator will be warned through the "DIAGNOSTIC" lamp.