Visual inspection
* Inspect the control unit for cracks, chips, or other physical damage.
* Check if all electrical connectors are connected securely.
Checking the connectors
* Use a multimeter to check the voltage and resistance at each connector.
* Compare the values obtained with the manufacturer’s specifications.
* Check for opens or short circuits.
Checking circuits
* Study the electrical diagram of the automatic transmission.
* Use a multimeter to check continuity between the control unit and the sensors, solenoids and actuators.
* Make sure all circuits are well connected.
Checking sensors and actuators
* Disconnect sensors and actuators from the control unit.
* Check the resistance or voltage of the sensors using a multimeter.
* Activate the actuators and check their mechanical operation.
Diagnostic scan
* Connect the diagnostic scanner to the OBD-II connector.
* Run diagnostics of the automatic transmission control unit.
*Please note that there are fault codes.
*Use information from your repair manual to interpret the codes.
Test drive
* Start the car and take it for a test drive.
* Pay attention to the operation of the automatic transmission in all switching modes.
* Check for noise, vibration or other shifting problems.
Additional checks
*If other checks do not reveal problems, you may need to perform the following additional steps:
* Isolating the automatic transmission control unit and testing it separately from other components.
* Replacement of the control unit with a known good one.
* Check battery voltage and grounding.
If after performing all these checks the problem still persists, contact a qualified mechanic for further diagnosis and repair.