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Chevrolet Silverado / GMC Sierra. Manual - part 1315
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
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 Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM, PCM or IPC replacement, setup and programming
CRUISE CONTROL MALFUNCTION
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.
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
The vehicle speed is greater than 40 km/h (25 mph).
The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The system voltage is within 9-16 volts.
The park brake or brakes are not applied.
Diagnostic Aids
In order to avoid misdiagnosis, inspect for the following:
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.
Inspect the cruise control switches for any sticking or binding conditions.
Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems
Description and Operation .
With the ignition ON, rotate the steering wheel to both steering stops while activating each
cruise control switch separately. With a scan tool, observe all cruise control switch
parameters in the BCM. Ensure that each cruise control switch activates and that each of the
displayed switch position parameters match the currently activated switch, and do not read
Error. This may aid in locating an intermittent fault within the inflatable restraint steering
wheel module coil.
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
IMPORTANT: Repair any brake system related symptoms and DTCs before
performing this diagnostic.
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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, cruise on/off switch ON. With a scan tool, 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. Road test the vehicle to ensure
the cruise control system functions as described in Cruise Control Description and Operation.
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.
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
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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. With the 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.
If any of the resistance measurements for the individual switches are not within the
listed resistance values, replace the cruise control switch assembly.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Steering Wheel Control Switch Assembly Replacement
Control Module References for BCM replacement, setup, and programming
IMPORTANT: The cruise control switch must be ON in order to properly
measure the resistance of the - /SET, the +/RES, and the Cancel
switches.
Function Switch
Minimum Resistance
Value
Maximum Resistance
Value
OFF
O.L.
O.L.
ON
6.6k Ohms
7.0k Ohms
-/SET
2.1k Ohms
2.5k Ohms
+/RES
3.6k Ohms
4.0k Ohms
Cancel
1.3k Ohms
1.7k Ohms
2008 Chevrolet Silverado 1500
2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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