For 1990-2009 cars
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

Brake switch information (signal) is sent to the transmission control module (TCM) by the Engine Control Module (ECM) through a communication network called controller area network (CAN). Circuits XR888 and XY888 are used to communicate CAN data between the ECM and TCM. When the TCM detects the loss of brake input from the ECM for a specified amount of time, then DTC P0703 will set. DTC P0703 is a type D DTC.

### Condition For Running The DTC

Transmission output speed is greater than 192 RPM.

### Condition For Setting The DTC

The TCM does not receive brake switch input from the ECM for 20 minutes.

### Action Taken When the DTC Sets

• | The ECM records the operating conditions in the Failure Records at the time of the DTC request from the TCM.

• | The TCM memory stores the DTC at the time of the first failure.

### Conditions for Clearing the MIL/DTC

• | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

• | The scan tool clears the DTC.

### Diagnostic Aids

• | Inspect the brake switch for proper adjustment.

• | Check for communication CAN code DTC U2105 or U2108.

### Test Description

The numbers below refer to the step number on the diagnostic table.

1. This step inspects for a short to ground in the brake switch circuit.

#### P0703 Brake Switch Circuit-Low

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to step 2 | Go to On-Board Diagnostic System Check
2 |

1. Install the Scan Tool .
2. With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the ECM/TCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Observe the Scan Tool Brake Switch status.
6. Apply and release the brake pedal several times.

Does the Brake Switch status display Applied when the brake pedal is depressed and Released when the pedal is released?

--

Go to Diagnostic Aids

Go to Step 3

3 |

1. Remove the HAZARD fuse.
2. Inspect the fuse for an open.

Is the fuse open?

--

Go to Step 4

Go to Step 5

4 | Check circuit A13, A401, and FB101 for a short to ground. Was the condition found? | -- | Go to Step 7 | Go to Step 5
5 | Check circuit A13, A401, and FB101 for an open. Was the condition found? | -- | Go to Step 7 | Go to Step 6
6 | Replace the brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Is the repair complete? | -- | Go to Step 8 | --
7 | Make the necessary wiring repairs. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 8 | --
8 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Observe the Scan Tool Brake Switch status.
4. Apply and release the brake pedal several times.

Does the Brake Switch status display Applied when the brake pedal is depressed and Released when the pedal is released?

--

System OK

Go to Step 1