Sierra 1500 2WD V6-4.3L (2008)
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
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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.
Circuit/System Description
The instrument panel cluster (IPC) illuminates the cruise control engaged indicator based on serial data messages received from the engine control
module (ECM) or the powertrain control module (PCM). The indicator is commanded ON when the cruise control system is controlling vehicle speed,
and turned OFF with the system disengaged.
Diagnostic Aids
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This diagnostic assumes the cruise control system is functioning normally and there are no DTCs set. If the cruise control system is
malfunctioning, refer to Cruise Control Malfunction. See: Cruise Control Malfunction
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If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Diagnostic Trouble Code Descriptions
Circuit/System Verification
Ignition ON, perform the IPC display test using a scan tool. Verify the indicator illuminates and turns OFF.
If the indicator does not operate as expected during this test, replace the IPC.
If the indicator functions normally during this test, replace the ECM/PCM.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures/Verification Tests and Procedures
Cruise Control Malfunction
Cruise Control Malfunction
Diagnostic Instructions
*
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
*
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
*
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The body control module (BCM) supplies battery voltage to the cruise control switch. The cruise control switch signal is an input to the BCM. The BCM
monitors the cruise control switch signal circuit in order to detect when the driver has requested to perform a cruise control function. The BCM detects a
specific voltage signal on the cruise control switch signal circuit when a switch is applied.
Conditions for Enabling Cruise Control
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The vehicle speed is greater than 40 km/h (25 mph).
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The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
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The system voltage is within 9-16 volts.
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The park brake or brakes are not applied.
Diagnostic Aids
Important: Repair any brake system related symptoms and DTCs before performing this diagnostic.
In order to avoid misdiagnosis, inspect for the following:
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Verify there are no DTCs set as current. If any DTCs are set as current, refer to Diagnostic Trouble Code (DTC) List - Vehicle and perform the
appropriate diagnostics/repairs before proceeding with symptom based diagnostics. See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Diagnostic Trouble Code Descriptions
