Circuit Description

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The powertrain control module (PCM) monitors the engine speed, and the transmission output shaft speed. The PCM calculates turbine shaft speed and torque converter clutch (TCC) slip speed by using inputs from the automatic transmission input shaft speed sensor (AT ISS), the automatic transmission output shaft speed sensor (AT OSS), and other transmission components. The forward clutch housing is used as the ISS rotor. Whenever the TCC is engaged, engine speed and turbine speed will closely match, indicating low TCC slip speed. In D3 with the TCC engaged, calculated transmission component slip can only occur in the torque converter. In D4 OVERDRIVE with the TCC engaged, transmission component slip can occur in the TCC or the fourth clutch assembly.

If the PCM detects an excessive TCC slip speed in D4 OVERDRIVE, when the TCC should be engaged, then DTC P0894 sets. DTC P0894 is a type C DTC. For California emissions, DTC P0894 is a type B DTC.