The most common causes of B2004 code being stored are due to a defective intermediate shaft speed sensor, output speed sensor, or input speed sensor.
To perform a thorough diagnosis, any transmission leaks should be repaired and the transmission should be filled with the proper amount and type of fluid (if the fluid smells really "burnt" and you are experienced enough to detect it, you may go ahead and condemn the transmission)
This will help to determine whether or not the malfunction is intermittent. After the codes are cleared, test drive the vehicle to see if the code returns
A suitable OBD-II scanner (or code reader), a digital volt/ohmmeter, and an oscilloscope will be most helpful in performing a successful diagnosis
Should all system circuitry and sensors check out and the transmission is in good working order, suspect a faulty PCM but keep in mind that PCM failure is rare and PCM replacement will require reprogramming.
Accelerator Pedal Position (APP) Sensor 1 Performance
Control Module Throttle Actuator Position Performance
Transmission Control Module Reprogrammable Memory
There will also be noise coming from the turning radiator fan and the belt that turn the fan blade. There are a multiple of other belt driven devices under the hood. An engine pulley is mounted to the engine of an automobile and drives all belts. Your car probably has a serpentine belt which is a continuous belt used to drive multiple peripheral devices. Parts or components should not be replaced with reference to only a B2004 DTC. The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing.
How to turn off B2004 check engine light ?
There are two ways to turn off the check engine light:
A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.