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5A-64 AUTOMATIC TRANSMISSION Default Transmission Operating Modes The TCU relies on accurate information from its inputs and complete control of its outputs to effectively control the The following symptoms of faults are the most obvious results of each fault under ‘normal’ conditions. There is always the possibility that a fault may not be detected. If undetected fault conditions are present, the 1 Throttle Fault l All shifts will occur as if a nominal throttle (approx. 44%) were applied for shift scheduling. l All shifts will be firm as full throttle and hence high engine torque is assumed. l The torque converter will be unlocked at all times. l All downshifts initiated by the shift lever will occur as though they were ‘automatic’ shifts. That is the engine braking effect will not occur until near the end of the shift. l Line pressure will always stay high (solenoid 6 OFF) to cope with assumed high throttle/torque. If a fault is undetected, the percent throttle is most likely to be interpreted as higher than actual, resulting in late 2 Throttle Not Learnt Fault The transmission operates from default throttle calibration values which results in the evaluation of the throttle being Other symptoms are: a. late upshifts and b. lock-up maintained at zero throttle when the vehicle speed is sufficiently high. 3 Engine Speed Fault l All shifts will be firm because an engine speed corresponding to peak engine torques is assumed. If a fault is undetected, the engine speed is likely to be interpreted as stalled resulting in soft shifting possibly with an 4 Vehicle Speed Sensor Fault l All shifts will be controlled by the shift lever with skip downshifts disabled and downshifts only allowed if the engine speed is low. Fourth gear will be inhibited. l The torque converter will be unlocked at all times. If a fault is undetected, the vehicle is likely to be interpreted as being stationary resulting in first gear operation at all 5 Gear Lever Fault (Inhibitor/PRNDL Switch) l The gear lever is assumed to be in the Drive position. l The transmission is limited to 2nd,3rd, and R gears only. l The rear band will apply at all times when the lever is shifted to P, R or N. (B2 inhibition and reverse lockout protection is disabled.) l The torque converter will be unlocked at all times. l Manually (gear lever) initiated downshifts will not be available. If a fault is undetected, the gear lever position is likely to be interpreted as being higher than actual. Where Park is the |