Atcu

ATCU

The ATCU monitors the operation of the automatic gearbox via four sensors:

The temperature of the automatic transmission fluid (ATF) is measured by the fluid temperature sensor. The fluid temperature sensor (C0243) receives a feed from the ATCU (C0932) on a WK wire. The temperature sensor return (C0243) to the ATCU (C0932) is via a KB wire. As the temperature of the ATF rises, so the resistance of the sensor decreases. The ATCU registers this drop in resistance and calculates the temperature of the ATF accordingly. For more information on the fluid temperature sensor, refer to the Automatic Gearbox – Jatco section of the System Description and Operation Workshop manual. Vehicle speed is measured by the vehicle speed sensor. The vehicle speed sensor (C0243) is connected to the ATCU (C0932) by a U wire. The speed sensor creates a sinusoidal waveform, with each positive phase of the waveform representing one tooth on the parking gear (19 per engine revolution). The ATCU uses this waveform to calculate vehicle speed. The sensor return (C0243) to the ATCU (C0932) is via a W then KB wire. For more information on the vehicle speed sensor, refer to the Automatic Gearbox – Jatco section of the System Description and Operation Workshop manual. Input shaft speed into the gearbox is measured by the turbine sensor. The turbine sensor (C0243) is connected to the ATCU (C0932) by an R wire. The turbine sensor creates a sinusoidal waveform, with 16 positive phases representing one input shaft revolution. The ATCU uses this signal along with a vehicle speed signal to calculate if the correct gear has been selected. The sensor return (C0243) to the ATCU (C0932) is via a U then KB wire. For more information on the turbine sensor, refer to the Automatic Gearbox – Jatco section of the System Description and Operation Workshop manual. The internal, or intermediate, transmission speed is measured by the intermediate sensor. The intermediate sensor (C0243) is connected to the ATCU (C0932) by an R wire. The intermediate sensor creates a sinusoidal waveform, with each positive phase of the waveform representing one tooth of the output gear (49 per revolution). The ATCU uses this signal to ensure the correct gear is engaged, and to monitor the amount of slip within the gearbox. The sensor return (C0243) to the ATCU (C0932) is via a B then KB wire. For more information on the intermediate sensor, refer to the Automatic Gearbox – Jatco section of the System Description and Operation Workshop manual.

Park

When park is selected, a main relay feed is able to flow from the transmission selector/inhibit switch (C0244) to the ATCU (C0932) and the selector indicator (C0675) on a KO wire. The 'P' symbol on the selector housing will now illuminate.

NOTE: On Canadian specification vehicles, a feed is also provided to the Central Control Unit (CCU) (C0593) on a KO wire. This input is used by the CCU to extinguish the daylight running lamps.