P0573-BRAKE SWITCH 1 STUCK OFF
For a complete wiring diagram, refer to the Wiring Information.
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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.
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When Monitored:
When vehicle speed cycles from 0 to 48 kph (30 mph) at least 10 times.
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Set Condition:
When the Powertrain Control Module (PCM) recognizes Brake Switch 1 is stuck in the high/off position. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes |
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| (B15) BRAKE SWITCH 1 SIGNAL CIRCUIT OPEN |
| (Z908) GROUND CIRCUIT OPEN |
| 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).
Diagnostic Test
| 1. | Start the engine. |
| 2. | Allow the engine to reach normal operating temperature. |
| 3. | With the scan tool, select View DTCs. |
| NOTE: | It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data. |
Is the DTC Active or Pending at this time?
Yes
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
| 1. | Turn the ignition off. |
| 2. | Disconnect the Stop Lamp Switch harness connector. |
| 3. | Measure the resistance between the (Z908) Ground circuit terminal and the (B15) Brake Switch 1 Signal circuit terminal in the Stop Lamp Switch. |
| 4. | Apply and release the brake pedal while monitoring the Ohmmeter. |
Does the resistance change from below 5.0 Ohms to an open circuit when pressing and releasing the brake pedal?
Yes
No
- Verify that there is good pin to terminal contact in the Switch and Control Module connectors. Replace the Stop Lamp Switch if no problems were found in the connectors.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
3. CHECK THE (B15) BRAKE SWITCH 1 SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
| 1. | Turn the ignition off. |
| 2. | Disconnect the PCM C1 harness connector. |
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.
CAUTION:
| 3. | Connect the Adapter, GPEC Diagnostic 10436 . |
| 4. | Measure the resistance of the (B15) Brake Switch 1 Signal circuit between the Stop Lamp Switch harness connector and the GPEC Adaptor |
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the (B15) Brake Switch 1 Signal circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
4. CHECK THE (Z908) GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
| 1. | Measure the resistance between the (Z908) Ground circuit and ground in the Stop Lamp Switch harness connector. |
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the (Z908) Ground circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
5. 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 there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Replace and program the Powertrain Control Module in accordance with the service information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).