Brake switch information is sent to the transmission control module (TCM) by the powertrain control module (PCM) through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the PCM and TCM. A fault in the CAN will not cause DTC P0703 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P0703.
When the PCM sends the TCM an invalid brake switch signal, then DTC P0703 will set. DTC P0703 is a type C DTC.
This diagnostic procedure supports the following DTC:
DTC P0703 Brake Switch Circuit
| • | No CAN DTC U0100. | 
| • | Trans. Protection Mode OFF. | 
| • | The ignition has been ON for at least 3 seconds. | 
The brake switch signal is invalid for 4 seconds.
| • | The TCM commands the brake signal off. | 
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. | 
| • | The TCM stores DTC P0703 in TCM history. | 
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring. | 
| • | The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM. | 
Step  | Action  | Yes  | No  | ||||
|---|---|---|---|---|---|---|---|
1  | Did you perform the Diagnostic System Check - Vehicle?  | Go to Step 2  | |||||
2  | 
 Important: 
 Did you record any ECM Failure Records?  | Go to Step 3  | |||||
3  | 
 Did DTC P0703 reset?  | Go to Step 4  | Go to Testing for Intermittent Conditions and Poor Connections  | ||||
4  | Did any other DTCs set?  | Go to Step 5  | |||||
5  | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Is the action complete?  | Go to Step 6  | --  | ||||
6  | Perform the following operation to verify the repair: 
 Does the DTC reset?  | Go to Step 2  | Go to Step 7  | ||||
7  | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed?  | System OK  |