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HOMESERVICE MANUALSCHEVROLET2001SUBURBAN C1500REPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESBODY CONTROL MODULESDIAGNOSTIC INFORMATION AND PROCEDURESPOWER MODE MISMATCHTEST DESCRIPTION
2001 Chevrolet Suburban C1500

Test Description

2001 Chevrolet Suburban C1500SECTION Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 4 

    This step tests for battery voltage on the signal circuits that are not required.

  2. 5 

    This step tests for no battery voltage on the required signal circuits.

  3. 6 

    If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.

  4. 7 

    This step eliminates open circuits as the cause of the malfunction.

Power Mode Mismatch

Step Action Yes No
Schematic Reference:  Body Control System Schematics  
1
  1. Install a scan tool.
  2. Turn OFF the ignition.
  3. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.
Does the displayed power mode parameter match the actual ignition switch position?		 Go to Step 2  Go to Step 4 
2
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.
Does the displayed power mode parameter match the actual ignition switch position?		 Go to Step 3  Go to Step 4 
3
IMPORTANT:

The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Turn the ignition switch to the CRANK position.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.
Does the displayed power mode parameter match the actual ignition switch position?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 4 
4 
IMPORTANT:

The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Turn OFF the ignition.
  2. Disconnect the PMM.
  3. Hold the ignition switch in the position that indicated the incorrect power mode.
  4. With a test lamp attached to a good ground, test the PMM ignition switch inputs for voltage. Refer to Body Control System Description and Operation .
Is voltage present on only the inputs specified for the ignition switch position?		 Go to Step 5  Go to Step 6 
5 
IMPORTANT:

The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Hold the ignition switch in the position that indicated the incorrect power mode.
  2. With a test lamp attached to a good ground, test the PMM ignition switch inputs for voltage. Refer to Body Control System Description and Operation .
Is voltage not present on any inputs specified for the ignition switch position?		 Go to Step 7  Go to Step 9 
6 
  1. Disconnect the ignition switch.
  2. Test the PMM ignition switch input circuits for a short to voltage. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.
  3. Test the PMM ignition switch circuits for a short between circuits. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 12  Go to Step 8 
7 
  1. Disconnect the ignition switch.
  2. Test the PMM ignition switch input circuits for an open. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 12  Go to Step 8 
8 Inspect for poor connections and terminal tension at the harness connector of the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections , and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 12  Go to Step 10 
9 Inspect for poor connections and terminal tension at the harness connector of the PMM. Refer to Testing for Intermittent Conditions and Poor Connections , and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 12  Go to Step 11 
10 Replace the ignition switch. Refer to Ignition Switch Replacement - On Vehicle in Steering Wheel and Column.
Did you complete the replacement?		 Go to Step 12  -
11
IMPORTANT:

After replacement of the PMM perform the set up procedure if required.

Replace the PMM. Refer to Control Module References .Did you complete the replacement?		 Go to Step 12  -
12
IMPORTANT:

The engine may start during this procedure. Turn the ignition OFF after verifying all power modes.

  1. Reconnect all disconnected components.
  2. With a scan tool, under the Diagnostic Circuit Check menu observe the Class 2 Power Mode parameter.
  3. Cycle the ignition switch through all possible positions one at a time.
Does the displayed power mode parameter match the actual ignition switch position?		 System OK Go to Step 1 
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.