Q: problems with changing gears

Hi there. The transmission is loosing power to the sensors and solenoids inside the transmission case. Go under the vehicle with the wheels chocked and check the transmission harness. Look for any debris, oil, moisture, broken or bent pins. If there is nothing wrong with the harness, then with the ignition switch on and the engine off, check for power at the harness with a digital volt ohm meter (DVOM). Also check for a ground in the harness with the DVOM. If there is power and ground, then the harness inside the transmission may be broken and is shorting out and needs replaced. Plus, check the circuit for the downshift solenoid to the transmission.

If the downshift solenoid is not functional, then the transmission may also lock out the shifting. If there is no power or ground, then turn the key off and check the battery terminals and the fuse box for any loose wire and blown fuses. If all wires and fuses are okay, then check for power and ground at the computer. If there is no power to the computer, then there is a broken wire between the computer and the fuse box. If there is power, check for power coming out of the computer. If there is power coming out of the computer then change the harness to the transmission. If there is no power coming out of the computer, then the computer has failed and need replaced. If you need further assistance diagnosing your vehicle, then seek out a professional, such as one from YourMechanic, to help you with your vehicle.