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

### Circuit Description

With the brake pedal applied, the brake lamp switch closes and the battery voltage supplies to terminal 39 of the TCM. When you release the brake, the brake switch opens and terminal 39 of the TCM removes the battery voltage.

### Conditions for Running the DTC

The Output Speed is greater than 192 RPM.

### Conditions for Setting the DTC

The brake switch remains open for longer than 20 Minutes.

### Action Taken When the DTC Sets

• | The MIL/STL will not illuminate.

• | 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 or any other non-emission related diagnostic.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:

• | Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault.

### Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

1. In the previous step, the parameter did not change during the functional test. This step determines whether the circuit has failed high or failed low.

2. Check both circuits for a short to ground if the fuse for the supply circuit is open.

#### DTC P0703 - Brake Switch Circuit

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

1. Turn off the engine.
2. Turn on the ignition.
3. Observe the Brake Switch on the scan tool.
4. Apply and release the brake pedal.

Does the Brake Switch indicate Released when you release the brake pedal, and Applied when you apply the brake pedal?

--

No trouble found

Refer to Diagnostic Aids

Go to Step 3

3 | Does the Brake Switch parameter always indicate Released? | -- | Go to Step 4 | Go to Step 8
4 |

1. Disconnect the Brake switch.
2. Use a DVM J 39200 in order to measure the voltage at the B+ supply circuit in the brake switch harness connector.

Does the DVM indicate the specified value?

B+

Go to Step 5

Go to Step 10

5 | Use a fused jumper in order to jumper the B+ supply circuit to the Brake switch signal circuit while monitoring Brake Switch on the scan tool. Does the scan tool indicate Applied? | -- | Go to Step 14 | Go to Step 6
6 |

1. Turn off the ignition.
2. Disconnect the TCM.
3. Use a DVM J 39200 in order to check the continuity of the Brake switch signal circuit from the Brake switch harness connector to the TCM harness connector.

Is the continuity indicated?

--

Go to Step 7

Go to Step 11

7 | Use a DVM J 39200 in order to check the continuity between the Brake switch signal circuit and ground. Does the DVM indicate continuity? | -- | Go to Step 12 | Go to Step 18
8 | Disconnect the Brake switch. Does the scan tool indicate Released? | -- | Go to Step 14 | Go to Step 9
9 |

1. Turn off the ignition.
2. Disconnect the TCM.
3. Turn on the ignition with the engine off.
4. Probe the Brake switch signal circuit with the test light J 35616-200 connected to ground.

Does the test light illuminate?

--

Go to Step 13

Go to Step 19

10 | Repair the B+ supply circuit to the Brake switch. Is the action complete? | -- | Go to Step 20 | --
11 | Repair the open/high resistance Brake switch signal circuit. Is the action complete? | -- | Go to Step 20 | --
12 | Repair the Brake switch signal circuit shorted to ground. Is the action complete? | -- | Go to Step 20 | --
13 | Repair the Brake switch signal circuit shorted to B+. Is the action complete? | -- | Go to Step 20 | --
14 | Check the Brake switch for proper adjustment. Refer to Engine Electrical, On-Vehicle Service, Brake switch. Was a problem found and corrected? | -- | Go to Step 20 | Go to Step 15
15 |

1. Disconnect the brake switch.
2. Connect the DMM to terminal 2 brake switch signal circuit 1.

Does the DMM indicate the specified value?

B+

Go to Step 16

Go to Step 17

16 | Repair the short to B+ on circuit FB 200, FB 500, or FB 10. Is the action complete? | -- | Go to Step 20 | --
17 | Replace the Brake switch. Is the action complete? | -- | Go to Step 20 | --
18 | Check the TCM harness connector for a poor connection or poor terminal tension. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure. Was a problem found and corrected? | -- | Go to Step 20 | Go to Step 17
19 | Replace the TCM. Refer to Automatic Transmission, On-Vehicle Service, TCM . Is the action complete? | -- | Go to Step 20 | --
20 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Start the engine.
4. Operate the vehicle within the conditions required for this diagnostic to run. Refer to Conditions for Running the DTC.
5. Check for any DTCs.

Is DTC P0703 set?

--

Go to Step 2

Go to Step 21

21 | Were there any additional DTCs noted during the Powertrain or Transmission OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | Go to Step 22
22 | Does the Transmission now function properly? | -- | System OK | Go to Functional Test