3176C and 3196 Industrial Engines Caterpillar

Illustration 1	g00281190
(1) Primary speed/timing sensor. (2) Backup speed/timing sensor.

If primary speed/timing sensor (1) cannot sense engine speed, the "DIAGNOSTIC" lamp will indicate a diagnostic fault code which will be logged in the ECM memory.

If primary speed/timing sensor (1) cannot sense engine speed, the automatic default will use backup speed/timing sensor (2). The backup speed/timing sensor will be used until the primary speed/timing sensor is replaced.

Speed/Timing Sensor Failure

If any of the following conditions are present, a speed/timing sensor failure 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 primary speed/timing sensor failure. The operator will be warned through the diagnostic lamp.