For 1990-2009 cars

### Circuit Description

The brake switch is used to indicate brake pedal status to the transmission control module (TCM). The brake switch is a normally open switch. Applying the brake pedal closes the switch, supplying voltage to the TCM. Releasing the brake pedal interrupts voltage to the TCM."

The TCM will store a P0703 every time the TCM is energized. Once the TCM sees the brake switch transition from "Released" to "Applied," with the ignition switch On, then the P0703 will be cleared. If the Scan Tool is displaying the P0703 DTC, ensure that you press and release the brake before using the following diagnostic procedure. Only use the diagnostic procedure if the P0703 DTC is not cleared after initially pressing and releasing the brake pedal.

Important: When the brake pedal was applied prior to or during the connection of the scan tool to the vehicle, a P0703 will disappear from the scan tool screen. If the system is operating normally, the code will then be deleted once the brake pedal is applied with the scan tool connected.

Important: Before diagnosing DTC P0703, verify the proper operation of the rear brake lamps. If the brake lamps are functioning normally, Do Not proceed with this test. Clear the DTC from the scan tool and proceed on to the next DTC.

### Conditions for Setting the DTC

• | Brake switch stuck to closed

• | Brake switch wiring harness shortage to ground

• | Immediately after the above condition occurs

### Action Taken When the DTC Sets

• | No lamp control required, but diagnostic information should be stored immediately when malfunction is detected.

• | The TCM assumes that the brake light is always active.

### Conditions for Clearing the Hold Lamp/DTC

Using a scan tool can clear history DTCs.

### Diagnostic Aids

• | Inspect the poor wiring harness connection for TCM connectors and transaxle wiring connectors.

• | Inspect the improperly formed or damage terminals.

#### DTC P0703

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Perform the Diagnostic System Check. Is the check complete? | -- | Go to Step 2 | Go to Diagnostic System Check - Automatic Transmission
2 |

1. Install the scan tool.
2. Turn the ignition ON, with the engine OFF.
3. Record, then clear, the DTCs.
4. Select scan tool transmission "DATA DISPLAY."

Did the brake switch status change from Applied to Release?

--

Go to Step 3

Go to Step 4

3 |

1. With the scan tool still connected.
2. Turn the ignition OFF.
3. After turning the ignition OFF, turn ignition ON, engine OFF.
4. Using the scan tool, check for transmission DTC's.

Important: If the DTC did not reset, and the brake lamps are functioning normally, Do Not Replace the Brake Switch

Did the DTC P0703 reset?

--

Go to Step 4

Go to Step 17

4 | Inspect the EF13. Is the fuse blown? | -- | Go to Step 5 | Go to Step 6
5 | Replace the fuse. Is the action complete? | -- | System OK | --
6 |

1. Turn the ignition OFF.
2. Disconnect the C102 wiring connector and the brake switch wiring connector.
3. Measure the resistance between the terminal D6 of the C102 connector and the terminal 2 of the brake switch wiring connector.

Is the resistance approximately equal to the specified value?

0 ohms

Go to Step 8

Go to Step 7

7 | Repair the open circuit between the C102 connector and the brake switch connector. Is the action complete? | -- | System OK | --
8 |

1. Turn the ignition ON, with the engine OFF.
2. Measure the voltage of the C102 connector, 6 terminal.

Is the voltage within the specified value?

11-14 V

Go to Step 9

Go to Step 10

9 | Repair the short to power between the C102 connector and the brake switch connector. Is the action complete? | -- | System OK | --
10 |

1. Turn the ignition OFF.
2. Disconnect the brake switch wiring connector and transmission control module (TCM) wiring connector.
3. Measure between the brake switch connector, terminal 4 and TCM connector, terminal A5.

Is the resistance approximately equal to the specified value?

0 ohms

System OK

Go to Step 11

11 | Repair the open or short to ground between brake switch connector and TCM. Is the action complete? | -- | System OK | --
12 |

1. Turn the ignition ON, with the engine OFF.
2. Measure the voltage of the brake switch wiring connector, terminal 4.

Is the voltage within the specified value?

11-14 V

Go to Step 13

Go to Step 14

13 | Repair the short to power between the brake switch wiring connector and TCM. Does the system function correctly? | -- | System OK | Go to Step 14
14 | Using a ohmmeter, check the brake pedal switch for proper operation. Refer to Automatic Transmission Controls Schematics Is the switch operating correctly? | -- | Go to Step 17 | Go to Step 15
15 | Replace the brake switch. Refer to Stop Lamp Switch Replacement Is the action complete? | -- | System OK | --
16 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 15 | --
17 |

1. After the repair, use a scan tool "clear info" function.
2. Road test the vehicle.
3. Review the "DTC info".

Has the last test failed or is the current DTC displayed?

--

Go to Step 2

System OK