PRE-RELEASE
DTC P0572 or P0573
| DTC P0572 or P0573 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| 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 |
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Stop Lamp Switch Signal
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P0572
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P0572
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P0573
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-
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| Circuit/System Description |
The stop lamp switch signal circuit is a B+ input from the body control module (BCM) to the engine control module (ECM). The ECM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The BCM monitors the brake pedal position sensor to determine when the brake pedal is applied. When the brake pedal is applied, the BCM supplies B+ on the stop lamp switch signal circuit and also sends a serial data message to the ECM indicating that the brake pedal has been applied.
| Conditions for Running the DTC |
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The engine is running.
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Battery voltage is greater than 11.5 V.
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| Conditions for Setting the DTC |
The ECM detects either a low voltage signal on the stop lamp switch signal circuit when the serial data message from the BCM indicates the brakes are applied, or 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.
| Action Taken When the DTC Sets |
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The malfunction indicator lamp (MIL) will not illuminate.
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The cruise control system is disabled.
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| Conditions for Clearing the DTC |
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The condition responsible for setting the DTC no longer exists.
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A history DTC will clear after 40 malfunction-free ignition cycles have occurred.
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| Reference Information |
Schematic Reference
Cruise Control Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool Reference
Control Module References for scan tool information
| Circuit/System Testing |
| 1. |
Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
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| 2. |
Connect a test lamp between the appropriate signal circuit terminal listed below and ground.
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Terminal 85 (LLU)
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Terminal 52 (LDK, LBW)
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Terminal 24 (LBY)
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Terminal 25 (LDE, 2H0)
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Terminal 55 (LE5, LTD)
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Terminal 38 (LBS, LBX, LCD)
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| 3. |
Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.
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| 4. |
If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
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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 K9 Body Control Module.
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| 6. |
If all circuits test normal, replace the K20 Engine Control Module.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for control module replacement, setup and programming
