Drivable short-term, but fix now to avoid damage.
P0740 means there's a problem in the torque converter clutch circuit or its solenoid. This clutch normally 'locks' the engine and transmission together at cruising speed for efficiency. When it fails, you can lose fuel economy, feel slipping, and risk overheating the transmission fluid.
$150 – $1200
Varies by vehicle and root cause.
Short trips are usually okay, but driving long-term can overheat the fluid and worsen wear. It's safer to have it diagnosed soon to avoid a pricier torque converter repair.
Replacing the solenoid or fixing wiring often runs $150-$500. If the torque converter itself needs replacing, costs can climb to $600-$1,200 due to the labor involved.
It's a high-priority code. While the car may still drive, ignoring it can lead to overheating and damage to the transmission, turning a moderate fix into a major one.
It's a component that locks the engine directly to the transmission at higher speeds to save fuel and reduce heat. P0740 means the circuit controlling that lockup isn't working right.