P1572

P1572-BRAKE PEDAL STUCK ON

Theory of Operation

The Stop Lamp Switch consists of three separate switches. The Powertrain Control Module (PCM) independently monitors two of these switches through the Brake Signal 1 and Brake Signal 2 circuits. When the brake pedal is released, both switches monitored by the PCM are closed. When the brake pedal is pressed, both switches are open. If the PCM detects one switch being closed while the other is open, a fault condition has occurred and the PCM will take the appropriate action.

- 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 Powertrain Control Module (PCM) detects that the actual state of Brake Signal 1 or Brake Signal 2 does not match the desired state during monitoring.

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE
1. Turn the ignition on.
2. Using the scan tool, read the Brake Switch Filtered Switch State and Brake Switch 2 Filtered Switch State status while pressing and releasing the brake pedal several times.

NOTE: The Brake Switch Filtered Switch State and Brake Switch 2 Filtered Switch State status should both read Off with the brake pedal released and On with the brake pedal pressed.

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

Yes

- Test complete, the condition of conditions that originally set the DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.

No - Brake Switch Filtered Switch State Incorrect

- Go To 3

No - Brake Switch 2 Filtered Switch State Incorrect

- Go To 8

No - Both Brake Switch States Incorrect

- Go To 2

2. BRAKE SWITCH ADJUSTMENT
1. Depress and hold the brake pedal in the depressed position.
2. Pull the brake lamp switch plunger all the way out of the switch housing to its fully extended position.
3. Release the brake pedal and lightly pull the pedal upward to its normal at-rest position. The pedal will set the plunger to the correct position as the pedal pushes the plunger into the switch housing. The switch plunger will make a light audible ratcheting noise as it self-adjusts.
4. Using the scan tool, read the Brake Switch Filtered Switch State and Brake Switch 2 Filtered Switch State status while pressing and releasing the brake pedal several times.

NOTE: The Brake Switch Filtered Switch State and Brake Switch 2 Filtered Switch State status should both read Off with the brake pedal released and On with the brake pedal pressed.

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

Yes

- Test complete.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 13

3. (Z911) GROUND CIRCUIT OPEN OR EXCESSIVE RESISTANCE

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 (Z911) Ground circuit in the Stop Lamp Switch harness connector.

NOTE: The test lamp must illuminate brightly. Compare the brightness to that of a direct connection to ground.

Does the test lamp illuminate brightly?

Yes

- Go To 4

No

- Repair the open or excessive resistance in the (Z911) Ground circuit.
- Perform the PCM Verification Test. PCM Verification Test.

4. (B15) BRAKE SIGNAL 1 CIRCUIT
1. Turn the ignition on.
2. Using the scan tool, read the Brake Switch Filtered Switch State status.

NOTE: The Brake Switch Filtered Switch State status should read On.

Does the Brake Switch Filtered Switch State match the status indicated above?

Yes

- Go To 5

No

- Go To 6

5. (B15) BRAKE SIGNAL 1 CIRCUIT

1. Connect a jumper wire between cavity 5 and cavity 6 in the Stop Lamp Switch harness connector.
2. Using the scan tool, read the Brake Switch Filtered Switch State status.

NOTE: The Brake Switch Filtered Switch State status should read Off.

Does the Brake Switch Filtered Switch State match the status indicated above?

Yes

- Go To 13

No

- Go To 7

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

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

Is the resistance below 100 Ohms?

Yes

- Repair the short to ground in the (B15) Brake Signal 1 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 14

7. (B15) BRAKE SIGNAL 1 CIRCUIT OPEN OR EXCESSIVE RESISTANCE

1. Disconnect the Stop Lamp Switch harness connector.
2. 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 much illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test lamp illuminate brightly?

Yes

- Go To 9

No

- NOTE: If the M37 fuse is open, make sure to check the (F941) Fused Ignition Switch Output (Run-Start) circuit and the (B16) Brake Signal 2 circuit for a short to ground.
- Repair the open or excessive resistance in the (F941) Fused Ignition Switch Output (Run-Start) circuit.
- Perform the PCM Verification Test. PCM Verification Test.

9. (B16) BRAKE SIGNAL 2 CIRCUIT
1. Using the scan tool, read the Brake Switch 2 Filtered Switch State status.

NOTE: The Brake Switch 2 Filtered Switch State status should read On.

Does the Brake Switch 2 Filtered Switch State match the status indicated above?

Yes

- Go To 10

No

- Go To 11

10. (B16) BRAKE SIGNAL 2 CIRCUIT

1. Connect a jumper wire between cavity 3 and cavity 4 in the Stop Lamp Switch harness connector.
2. Using the scan tool, read the Brake Switch 2 Filtered Switch State status.

NOTE: The Brake Switch 2 Filtered Switch State status should read Off.

Does the Brake Switch 2 Filtered Switch State match the status indicated above?

Yes

- Go To 13

No

- Go To 12

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

1. Turn the ignition on.
2. Measure the voltage between the (B16) Brake Signal 2 circuit and ground in the Stop Lamp Switch harness connector.

Is the voltage above 1.0 Volts?

Yes

- Repair the short to voltage in the (B16) Brake Signal 2 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No
Go To 14

12. (B16) BRAKE SIGNAL 2 CIRCUIT OPEN OR EXCESSIVE RESISTANCE

1. Turn the ignition off.
2. Disconnect the PCM C3 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 PCM Pinout Box 8815 to perform diagnosis.

3. Measure the resistance of the (B16) Brake Signal 2 circuit between the Stop Lamp Switch harness connector and the appropriate terminal of the PCM Pinout Box 8815.

Is the resistance above 5.0 Ohms?

Yes

- Repair the open or excessive resistance in the (B16) Brake Signal 2 circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 14

13. 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. Verify that there is good pin to terminal contact in the Switch and Control Module connectors.
5. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace the Stop Lamp Switch.
- Perform the PCM Verification Test. PCM Verification Test.

14. 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. Verify that there is good pin to terminal contact in the Switch and Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. PCM Verification Test.