GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 DTC 🢒 DTC P0703

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.

This DTC is stored at start-up. If the TCM receives a brake switch signal after start-up, the DTC will be stored in memory.

Conditions for Setting the DTC
    • The brake switch stuck to closed.
    • The brake switch wiring harness shortage to ground.
    • The brake switch wiring harness shortage to power.
    • Immediately after the above condition occur.

Action Taken When the DTC Sets
    • No lamp control required by diagnostic information should be stored immediately when malfunction is detected.
    • The TCM assumes that the brake light is always active.

Conditions for Clearing the 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 damaged terminals.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Automatic Transmission?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Record then clear the DTCs.
  4. Select scan tool transmission data display.
  5. Disconnect the brake switch connector.

Did the brake switch status change from ON to OFF?

--

Go to Step 3

Go to Step 4

3
  1. Replace the brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.
  2. After the ignition is OFF, Turn ON the ignition, with the engine OFF.

Is the DTC reset?

--

Go to Step 4

Go to Step 15

4

Inspect the EF19.

Is the fuse blown?

--

Go to Step 5

Go to Step 6

5

Replace the fuse.

Is the replacement complete?

--

System OK

--

6
  1. Turn OFF the ignition.
  2. Disconnect the C102 wiring connector and the brake switch wiring connector.
  3. Measure the resistance between the terminal D5 of the C102 connector and the terminal 3 of the brake switch wiring connector.

Is the resistance within the specified range?

∞ohms

Go to Step 8

Go to Step 7

7

Repair the open circuit between the C102 connector and the brake switch wiring connector.

Is the action complete?

--

System OK

--

8
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage of the C102 connector, D5 terminal.

Is the voltage within the specified range?

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

Is the resistance within the specified range?

∞ohms

System OK

Go to Step 11

11

Repair the open or short to ground between the brake switch connector and the TCM.

Is the action complete?

--

System OK

--

12
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage of the brake switch wiring connector terminal 4.

Is the voltage within the specified range?

11-14 V

Go to Step 13

Go to Step 14

13

Repair the short to power between the brake switch wiring connector and the TCM.

Is the action complete?

--

System OK

--

14

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the action complete?

--

Go to Step 15

--

15
  1. After the repair, use the scan tool Clear Info function and road test the vehicle.
  2. Review the DTC Info.

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

--

Go to Step 2

System OK