Chevrolet Silverado / GMC Sierra. Manual — part 1309
DIAGNOSTIC STARTING POINT - CRUISE CONTROL
Begin the system diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic
System Check will provide the following information:
The identification of the control modules which command the system
The ability of the control modules to communicate through the serial data circuit
The identification of any stored DTCs and their status
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the
system and where the procedure is located.
DTC B3794
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B3794 08
Cruise Control Function Request Circuit Signal Invalid
DTC B3794 61
Cruise Control Function Request Circuit Actuator Stuck
Diagnostic Fault Information
Stuck
DTC B0835
B0835 00: Cruise Control System Active Indicator Circuit
DTC P0571
P0571 00: Cruise Control Brake Switch Circuit
DTC P0572 or P0573
P0572 00: Brake Switch Circuit 1 Low Voltage
P0573 00: Brake Switch Circuit 1High Voltage
DTC P0575
P0575 00: Cruise Control Switch Signal Circuit
DTC P0703
P0703: Brake Switch Circuit
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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 Running the DTC
The ignition is ON.
The cruise switch is ON.
Conditions for Setting the DTC
B3794 08
The BCM detects an invalid voltage signal on the cruise control switch signal circuit is present
for 0.5 second.
B3794 61
The BCM detects an valid voltage signal on the cruise control switch signal circuit is present for
greater 60 seconds.
Action Taken When the DTC Sets
The BCM stores the DTC information into memory when the diagnostic runs and fails.
The malfunction indicator lamp (MIL) will not illuminate.
The Cruise Control System is disabled.
Conditions for Clearing the DTC
The DTC becomes history when the conditions for setting the DTC are no longer present.
Circuit
Short to
Ground
High
Resistance
Open
Short to
Voltage
Signal
Performance
Cruise Control Switch
Supply Voltage
1
B3794 08
1
-
B3794 08
B3794 61
Cruise Control Switch Signal
1
B3794 08
1
B3794 08
B3794 08
B3794 61
1. Cruise Control Inoperative/Malfunctioning
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The history DTC clears after 100 malfunction-free warm-up cycles.
Reference Information
Schematic Reference
Cruise Control Schematics
Steering Wheel Secondary/Configurable Control Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool Cruise Control Switch parameter in the BCM. While pressing
each of the cruise control switches, the scan tool display should change to display the current
switch being actuated.
Circuit/System Testing
1. Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable
Restraint Steering Wheel Module Replacement .
2. Disconnect the harness connector at the cruise control switch.
3. Ignition ON, test for B+ between the supply circuit terminal 1 and ground.
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
If less than the specified range, test the supply circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the BCM.
4. Verify the scan tool Cruise Control Switch parameter is OFF.
If not the specified value, test the signal circuit terminal 3 for a short to voltage. If the
circuit tests normal, replace the BCM.
5. Ignition OFF, connect the harness connector at the cruise control switch.
6. Ignition ON, cruise control switch ON, observe the scan tool Cruise Control Switch
parameter. The parameter should display ON.
If not the specified value, test the signal circuit terminal 3 for a short to ground or an
open/high resistance. If the circuit tests normal, test or replace the cruise control
switch.
7. Observe the scan tool Cruise Control Switch parameter while pressing the RES + portion of
the cruise control switch. The parameter should display Resume.
If not the specified value, test or replace the cruise control switch.
8. Observe the scan tool Cruise Control Switch parameter while pressing the SET - portion of
the cruise control switch. The parameter should display Set.
If not the specified value, test or replace the cruise control switch.
9. Observe the scan tool Cruise Control Switch parameter while pressing the Cancel portion of
the cruise control switch. The parameter should display Cancel.
If not the specified value, test or replace the cruise control switch.
10. If all circuits and the component test normal, replace the BCM.
Component Testing
1. Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable
Restraint Steering Wheel Module Replacement .
2. Remove the steering wheel cruise control switch. Refer to Steering Wheel Control Switch
Assembly Replacement .
3. Connect a DMM between terminals 1 and 3 of the cruise control switch. Cruise control
ON/OFF switch ON, measure the resistance while individually activating and holding each
cruise control function switch and compare the resistance reading to the values in the table
for the appropriate switch.
IMPORTANT: The cruise control switch must be ON in order to properly
measure the resistance of the -/SET, the +/RES, and the Cancel
switches.
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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