Volvo 850 AW50-42LE Auto Transmission Diagnosis
Transaxle is a 4-speed overdrive electronically controlled automatic transaxle. Transaxle consists of lock-up torque converter, oil pump, 3 planetary gear sets, clutch and brake units, accumulator pistons, valve body and 4 electronic valve body solenoids. Valve body with solenoids and Transaxle Control Module (TCM) are used for controlling transaxle operation. Solenoids are controlled by TCM.
TCM receives input signals from various components to determine transaxle shift points and torque converter lock-up. Components consist of mode selector switch, throttle position sensor, engine speed (RPM) sensor, vehicle speed sensor, gear position sensor, transaxle oil temperature sensor, brake switch and kickdown switch. See Fig. 2.
Transaxle is equipped with a mode selector switch. Switch is used for normal, high performance and winter driving conditions. Transaxle is also equipped with a shift lock and key interlock system. Shift lock system prevents shift lever from being moved from Park position unless brake pedal is applied. In case of malfunction, shift lever can be released by depressing shift lock override button, located near shift lever. Key interlock system prevents ignition switch from being moved from ACC to LOCK position unless shift lever is in Park position.
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