Diagnostic Instructions
DTC Descriptors
DTC P0572 : Brake Switch Circuit 1 Low Voltage
DTC P0573: Brake Switch Circuit 1 High Voltage
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
Stop Lamp Switch Signal
| P0572
| P0572
| P0573
| --
|
Circuit/System Description
The brake pedal position (BPP) sensor is used to sense the action of the driver application of the brake pedal. The BPP sensor provides an analog voltage signal that will increase as the brake pedal is applied. The instrument panel module (IPM) provides
a low reference signal and a 5-volt reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the IPM will apply battery voltage to the center high mounted stop lamp (CHMSL), transmission
control module (TCM), engine control module (ECM), and stop lamp relay. When the stop lamp relay receives battery voltage from the IPM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the stop lamps
fuse to illuminate the stop lamps. Ground for the left stop lamp and CHMSL is provided at G402 and the right stop lamp is grounded at G401.
Conditions for Running the DTC
| • | Battery voltage is greater than 11.5 volts. |
Conditions for Setting the DTC
P0572
The ECM detects a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied.
P0573
The ECM detects a high voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are not applied.
Actions Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The cruise control system is disabled. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear once 40 malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Exterior Lights Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
With a scan tool, command the stop lamps ON and OFF. The stop lamps should turn ON and OFF when changing between the commanded states.
Circuit/System Testing
- Ignition OFF, disconnect the harness connectors at the appropriate control modules listed below.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
| • | ECM terminal 7 - with LH2/LC3 |
| • | ECM terminal 52 - with LLT |
- Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
| ⇒ | If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the stop lamp relay. |
| ⇒ | If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the stop lamp relay. |
- Ignition OFF, connect the harness connector at the TCM.
- Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
| • | ECM terminal 7 - with LH2/LC3 |
| • | ECM terminal 52 - with LLT |
- Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
| ⇒ | If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the TCM. |
| ⇒ | If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TCM. |
- If all circuits test normal, replace the ECM.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
