Clean Tachometer Output (CTO)
WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, 2011 Ford Fusion, 2010 Mercury Milan, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) uses a crankshaft position (CKP) sensor input to calculate the engine speed. The engine speed information is then output to the TCM through the CTO circuit, as a frequency signal. The PCM also broadcasts a redundant engine speed message to the TCM over the controller area network (CAN) communication link. When the broadcasted engine speed disagrees with the hardwired CTO signal, or when the CTO circuit concern condition is detected, the TCM stores an appropriate diagnostic trouble code (DTC).