Need help to fix Radio Controlled / Remote Controlled Toy Car

The car runs on 6.4V battery. It is all wheel drive car - all four wheels turn when throttle is pushed to drive forward or backward. There are two motors that allow to achieve this, one is located at the front of the car and the other one is at the back of the car. These two motors work fine and there is no issue with the the forward and backward movement. The problem is that the steering wheel of the remote control does not turn the wheels. The steering is controlled by a 3rd motor that is mounted at the front of the car. The motor itself works fine. I tested it by supplying 6.4V directly to the "+" and "-" pins of the motor and by supplying 6.4V to the two pins on the circuit board (see #1 of the attached image). I have another same exact remote car and to exclude the possibility that the remote control itself is faulty, I tested the other car with both remote controls, and the other car turns fine with either of the them. My conclusion is that either the radio signal receiver on the car is broken or some other component of the circuit board has gone bad. I have attached two pictures that show the circuitboard. The comments below explain the numbers and arrows in the picture: 1. If I supply 6.4V to these pins, then motor that controls the steering starts to work. 2. Antenna 3. This little conduit has bunch of wires in it including the two wires from point #4 and 7 other wires that I believe allow to steer the car. 4. Power supply for the front motor and for the back motor which allow the car to go forward or backwards in all wheel drive.