P0703 - TORQUE CONVERTER/BRAKE SWITCH B - CIRCUIT MALFUNCTION

The brake switch provides a signal when the brake pedal is pressed. It tells the vehicle computer to apply or release the Torque Converting Clutch (TCC) as appropriate.

As soon as the brake pedal is pressed, the control module detects a preset voltage signal, which is sent to the Engine Control Module (ECM) as serial data on the status of the brake lights. The control module receives a signal from the switch, indicating that the driver has depressed the brake pedal. Typically, the switch is always closed and receives voltage through a fused circuit. For this reason, the control module observes the ignition voltage when the brake pedal is depressed.

The DTC code P0703 OBDII is set when the control module does not get the brake-pedal shift signal so the Check Engine light will illuminate. This is a high/low signal, and it is when the computer gets or does not get the voltage signal respectively.

• Warning Lighting (MIL).
• The brake light does not light up.
• TCC lockout may not be available.
• Lowers fuel efficiency.
• Transmission change patterns are erratic.

The fault code P0703 OBD2 is set because of these reasons:

• A bad adjustment of the brake switch.
• Defective brake switch cables or connectors.
• The brake switch may be defective.
• Maybe the fuse link is blown or the fuse is damaged

To solve the failures linked to the error code P0703 OBDII, you have to follow these steps:

• Check for TSB (Technical service bulletins) for your particular vehicle.
• Check the brake light wiring and all related cables. Also, check the fuses in the stop light system. If there are problems with the fuses, you should change them, then clear the code.
• Check the battery voltage in the brake switch input circuit by using a DVOM. Then, consult your vehicle service manual to determine the brake switch setting. If there is battery voltage in the input circuit, press the brake pedal and check for voltage in the output circuit. If there is no voltage in the output circuit, the brake switch may be misadjusted or defective. Repair or replace as necessary.