What does p0742 mean on a Chevy Impala?

Answer 1

P0742 means that your torque converter clutch circuit (TCC) is or was stuck on. In other words, the lock-up torque converter was engaged when it wasn't supposed to be.

The torque converter uses Transmission Fluid at lower speeds to transfer motion from the part of the transmission connected to the engine to the parts of the transmission connected to the drive shafts. This is what allows you to stop your car at a stop light without having the car die.

When the torque converter engages ("locks-up"), a clutch engages, creating a mechanical connection that makes both parts move together more efficiently at higher speeds (above ~49 mph). This allows you to get better gas mileage on the highway, since the fluid coupling is not very efficient at those speeds.

If your TCC fails to disengage or engages when it is not supposed to, it will set this code. You may notice the car chuggling at lower speeds or dying at stops.

This problem may be caused by a failing TCC solenoid in the transmission. The 4T65E transmission in Impalas is completely electronically controlled. However, it may also be caused by other transmission problems.