Engine Speed (Hard-Wired and Bussed Input)

For 1997 and prior MY, the TCM uses both direct engine speed input from the Crankshaft Position Sensor, as well as engine speed input from the PCM over the Communication Bus. The direct input is required to provide immediate information for use by the TCM control logic. The Bussed engine speed data is used by the TCM fail-safe logic to confirm that the direct engine speed data is valid.

Beginning in 1998 MY, the PCM sends an engine speed signal to the TCM across the PCI Bus and the TCM does not receive a direct input from the CKP Sensor.