C12 Marine Engines Caterpillar

The Throttle Position Sensor (TPS) sends a signal to the Electronic Control Module (ECM). The signal is required by the engine speed governor. The TPS signal is used by the ECM in order to calculate the engine rpm that is desired. The TPS is calibrated during the initial installation of the engine.

Throttle Position Sensor Failure

A throttle position sensor failure may have occurred if any of the following conditions are present:

• The output of the TPS is open.

• The TPS is shorted to ground or to supply.

• The TPS has missing pulses or extra pulses.

An intermittent failure causes engine speed drop outs. The ECM will perform the following process:

• The ECM will detect the failure of the TPS.

• The ECM will warn the operator of the failure through the diagnostic lamp.

• The ECM will set the engine rpm to low idle.

If a TPS fails in a twin engine application, the operator can use a synchronization switch to transfer the throttle control to the second TPS. Both engines can then be controlled with the second throttle. If both throttle position sensors fail, the engine rpm will be reduced to low idle.