Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the P0740 Buick code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
The Torque Converter Clutch (TCC) pressure control solenoid is part of the control solenoid valve assembly which has no serviceable parts. The TCC pressure control solenoid is a normally low-pressure control solenoid. The TCC pressure control solenoid regulates the transmission fluid to the TCC regulator valve in the lower valve body and the TCC control valve in the pump cover. When vehicle operating conditions are appropriate to apply the converter clutch, the Transmission Control Module (TCM) will increase TCC pressure control current flow (duty cycle) to the TCC solenoid. The TCC pressure control solenoid directs fluid pressure to move the TCC control valve to the apply position and moves the TCC regulator apply valve to the regulating position. The TCC regulator valve regulates TCC apply fluid pressure proportional to TCC solenoid pressure. When the TCC is fully applied, the engine is coupled directly to the transmission. TCC release is accomplished by the Transmission Control Module decreasing current flow to the TCC pressure control solenoid. This results in decreasing the applied pressure which allows the TCC control valve to move to the release position. The Transmission Control Module calculates torque converter slip speed based on engine speed and transmission input shaft speed.
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