P0740 Fault in the torque converter lock-up clutch wiring

By: Diagno editorial team · Updated: 2026-10-15

P0740 means: Fault in the torque converter lock-up clutch wiring. The torque converter lock-up clutch connects the engine and gearbox directly at motorway speeds to save fuel. Drive gently and have the car checked soon. The repair usually costs about €150–1500 in Estonia. The most common cause: gearbox oil is old or low.

What it means

The torque converter lock-up clutch connects the engine and gearbox directly at motorway speeds to save fuel. The clutch isn't engaging or is slipping.

What could be wrong

1. 1Gearbox oil is old or low
2. 2Lock-up clutch solenoid
3. 3Torque converter is worn

What you can check yourself

If the revs flare up and down at a steady motorway speed, mention it when you book. Best left to a workshop. It needs a diagnostic tool and experience.

How we fix it

1. We check the oil and the solenoid
2. We change the gearbox oil
3. If needed, we repair the torque converter

Standard SAE description: Torque Converter Clutch Circuit Malfunction