P0703-BRAKE SWITCH 2 PERFORMANCE

Special Tools: Click to display a list of tools used in this procedure

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Powertrain Control Module (PCM) monitors the vehicle braking via the Stop Lamp Switch. For accuracy, the PCM monitors two separate brake switch signals. The operating mode of these signals are as follows:

Brake Switch Signal 1 operation: The PCM sends out a 12 Volt, low amperage signal, which may not illuminate a test light, on the (B15) Brake Switch 1 circuit. The PCM monitors the voltage on this circuit to indicate if the brake pedal is depressed or released. When the brake pedal is released, the (B15) Brake Switch 1 circuit is connected to the (Z914) ground circuit and the PCM reads Zero Volts on the (B15) Brake Switch 1 circuit. When the pedal is pressed, the path to ground is broken and the PCM reads 12 Volts on the (B15) Brake Switch 1 circuit.

Brake Switch Signal 2 operation: 12 Volts are sent on the (F941) Ignition Switch Start/Run circuit through the Stop Lamp Switch to the PCM on the (B16) Brake Switch 2 circuit. The PCM monitors the voltage on this circuit to indicate if the brake pedal is depressed or released. Zero Volts on the (B16) Brake Switch 2 circuit indicates to the PCM that the pedal is pressed, and 12 Volts indicate that the brake pedal is released.

When Monitored:
With the gear selector in drive, vehicle speed above a minimum value, and battery voltage greater than 10.4 volts.
Set Condition:
The PCM detects that the actual state of Brake Signal 1 or Brake Signal 2 does not match the desired state during monitoring. One trip fault.

Possible Causes
(B15) BRAKE SIGNAL 1 CIRCUIT SHORTED TO GROUND
(B16) BRAKE SIGNAL 2 CIRCUIT SHORTED TO VOLTAGE
(F202) FUSED IGNITION SWITCH OUTPUT (RUN-START) CIRCUIT OPEN OR HIGH RESISTANCE
(Z912) GROUND CIRCUIT OPEN OR HIGH RESISTANCE
(B15) BRAKE SIGNAL 1 CIRCUIT OPEN OR HIGH RESISTANCE
(B16) BRAKE SIGNAL 2 CIRCUIT OPEN OR HIGH RESISTANCE
STOP LAMP SWITCH
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure)

1. DTC IS ACTIVE

1.	Turn the ignition on.

2.	With the scan tool, monitor the Brake Signal 1 and Brake Signal 2 states while pressing and releasing the brake pedal several times.

Do the Brake Signal states change appropriately as the pedal is pressed and released?

Yes

Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 2

2. (B15) BRAKE SIGNAL 1 CIRCUIT

1.	Turn the ignition off.

2.	Disconnect the Stop Lamp Switch harness connector.

3.	Using a 12-volt test light connected to 12 volts, check the (B15) Brake Signal 1 circuit at the Stop Lamp Switch harness connector while pressing and releasing the brake pedal several times.

Does the test light change from illuminated to not illuminated as the brake pedal is pressed and released?

Yes

Go To 3

Go To 4

3. (B16) BRAKE SIGNAL 2 CIRCUIT

1.	Turn the ignition on.

2.	Using a 12-volt test light connected to ground, check the (B16) Brake Signal 2 circuit at the Stop Lamp Switch harness connector while pressing and releasing the brake pedal several times.

Does the test light change from illuminated to not illuminated as the brake pedal is pressed and released?

Yes

Go To 11

Go To 7

4. (Z914) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

1.	Turn the ignition off.

2.	Disconnect the Stop Lamp Switch connector.

3.	Using a 12-volt test light connected to 12 volts, check the (Z914) Ground circuit in the Stop Lamp Switch harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

Go To 5

Repair the open or high resistance in the (Z914) Ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

5. (B15) BRAKE SIGNAL 1 CIRCUIT SHORTED TO GROUND

1.	Measure the resistance between ground and the (B15) Brake Signal 1 circuit in the Stop Lamp Switch harness connector.

Is the resistance above 100 Ohms?

Yes

Go To 6

Repair the short to ground in the (B15) Brake Signal 1 circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

6. (B15) BRAKE SIGNAL 1 CIRCUIT OPEN OR HIGH RESISTANCE

1.	Turn the ignition off.

2.	Disconnect the Powertrain Control Module (PCM) C1 harness connector.

CAUTION:

Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

3.	Connect the Adapter, GPEC Diagnostic 10436 .

4.	Measure the resistance of the (B15) Brake Signal 1 circuit between the Stop Lamp Switch harness connector and the GPEC Adaptor.

Is the resistance below 5.0 Ohms?

Yes

Go To 10

Repair the open or high resistance in the (B15) Brake Signal 1 circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

7. (F941) FUSED IGNITION SWITCH OUTPUT (RUN-START) CIRCUIT OPEN OR HIGH RESISTANCE

1.	Turn the ignition off.

2.	Disconnect the Stop Lamp Switch connector.

3.	Turn the ignition on.

4.	Using a 12-volt test light connected to ground, check the (F941) Fused Ignition Switch Output (Run-Start) circuit in the Stop Lamp Switch harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

Go To 8

Repair the open or high resistance in the (F941) Fused Ignition Switch Output (Run-Start) circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

8. (B16) BRAKE SIGNAL 2 CIRCUIT SHORTED TO VOLTAGE

1.	Measure the voltage of the (B16) Brake Signal 2 circuit in the Stop Lamp Switch harness connector.

Is there any voltage present?

Yes

Repair the short to voltage in the (B16) Brake Signal 2 circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 9

9. (B16) BRAKE SIGNAL 2 CIRCUIT OPEN OR HIGH RESISTANCE

1.	Turn the ignition off.

2.	Disconnect the Powertrain Control Module (PCM) C1 harness connector.

CAUTION:

3.	Connect the Adapter, GPEC Diagnostic 10436 .

4.	Measure the resistance of the (B16) Brake Signal 2 circuit between the Stop Lamp Switch harness connector and the GPEC Adaptor.

Is the resistance below 5.0 Ohms?

Yes

Go To 10

Repair the open or high resistance in the (B16) Brake Signal 2 circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

10. STOP LAMP SWITCH

1.	Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Stop Lamp Switch and the Powertrain Control Module (PCM).

2.	Look for any chafed, pierced, pinched, or partially broken wires.

3.	Look for broken, bent, pushed out or corroded terminals.

4.	Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Replace the Stop Lamp Switch in accordance with the Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

11. POWERTRAIN CONTROL MODULE (PCM)

1.	Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Stop Lamp Switch and the Powertrain Control Module (PCM).

2.	Look for any chafed, pierced, pinched, or partially broken wires.

3.	Look for broken, bent, pushed out or corroded terminals.

4.	Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

P0703-BRAKE SWITCH 2 PERFORMANCE

Theory of Operation

Possible Causes