Sierra 3500 2WD V8-6.0L (2008)
5. Verify less than 1 ohm of resistance while pressing the adjustable pedal forward switch.
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If greater than 1 ohm of resistance test the switch supply and signal circuits for an open or high resistance. If the circuits test normal replace the
adjustable pedal switch.
6. Connect a DMM from the adjustable pedal switch supply circuit terminal C4 to the rearward switch signal circuit in connector C2 terminal E1.
7. Verify less than 1 ohm of resistance while pressing the adjustable pedal rearward switch.
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If greater than 1 ohm of resistance test the switch signal circuit for an open or high resistance. If the circuit tests normal replace the adjustable
pedal switch.
8. Connect the I/P junction block connectors.
9. Disconnect the adjustable pedal motor connector and connect a test lamp across the control circuit terminals in the harness connector.
10. Verify that the test lamp illuminates when the adjustable pedal switch is pressed in both directions.
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If the test lamp does not illuminate while the switch is pressed in both directions, test the control circuits for an open or high resistance. If the
control circuits test normal replace the left I/P junction block.
11. If the circuit tests are normal replace the adjustable pedal motor.
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
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Accessory Switch Replacement (with RPO SLT) Accessory Switch Replacement (without RPO SLT)
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Brake Pedal Assembly Replacement
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Instrument Panel Electrical Center or Junction Block Replacement - Left Side
Adjustable Pedals Inoperative (with Memory)
Adjustable Pedals Inoperative (with memory)
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 adjustable pedals assembly is moved forward or backward by a motor which is fixed to the brake pedal actuator with a drive cable to the accelerator
pedal actuator. The adjustable pedals motor is controlled directly by an h-bridge driver circuit within the memory seat module. In an inactive state both
of the outputs to the motor are supplied with a low current voltage of approximately 2.0 volts. The memory seat module controls the adjustable pedals
motor by applying battery voltage to one of the outputs and ground to the other. The adjustable pedals motor is bidirectional and the direction of the
pedal assembly travel is determined by which of the motor control circuits is switched to battery positive voltage while the other is grounded. The
adjustable pedals forward and rearward switches are inputs to the memory seat module. The memory seat module supplies the switch assembly with a
battery positive reference voltage. When the switch is operated to the forward or rearward direction, battery positive voltage is applied to the forward or
rearward switch signal inputs.
Circuit/System Verification
1. Install a scan tool and display the MSM adjustable pedal information.
2. Verify that none of the switches are displayed as Active while in an inactive state.
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If any of the switch inputs are Active, perform the Adjustable Pedal Switch Circuit Test.
3. Verify that the switch inputs are displayed as Active while the switch is pressed.
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If any of the switch inputs remain Inactive while the switch is pressed, perform the Adjustable Pedal Switch Circuit Test.
4. If the switch inputs to the MSM function normal, perform the Motor Control Circuit Test.
Circuit/System Testing
