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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 946 (BODY CONTROL SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B1440: POWER MODE MASTER INPUT CIRCUITS MISMATCHCONDITIONS FOR CLEARING THE DTC
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Conditions for Clearing the DTC

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Conditions for Clearing the DTC
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  • A current DTC clears when the malfunction is no longer present.
  • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.
DTC B1440

Step Action Yes No
Schematic Reference: Body Control System Schematics 
Connector End View Reference:  Body Control System Connector End Views  
1 Perform the Diagnostic System Check for the system exhibiting the symptom. Refer to Control Module References .
Did you perform the Diagnostic System Check?		 Go to Step 2  Go to Control Module References 
2
  1. Install a scan tool.
  2. Turn OFF the ignition.
  3. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that all inputs are inactive/Off?		 Go to Step 3  Go to Step 6 
3
  1. Install a scan tool.
  2. Turn the ignition switch to ACC.
  3. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that the Ignition 0 and Ignition Accessory inputs are active/On?		 Go to Step 4  Go to Step 8 
4
  1. Turn the ignition switch ON, with the engine OFF.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that the all inputs are active/On?		 Go to Step 5  Go to Step 8 
5
IMPORTANT: The engine may start in this step. Turn the engine OFF immediately after reviewing the input data.
  1. Turn the ignition switch to START.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that the Ignition 0 and Ignition 1 inputs are On and the Ignition Accessory input is inactive?		 Go to Step 11  Go to Step 8 
6
  1. Disconnect the ignition switch harness connectors.
  2. With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that any of the Ignition 0, Ignition 1 or Ignition Accessory inputs is active/On?		 Go to Step 7  Go to Step 9 
7
  1. Disconnect the body control module (BCM) harness connectors.
  2. Test the suspect ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 11 
8
  1. Disconnect the ignition switch connectors.
  2. Install a 3A fused jumper between the suspect circuits and an ignition switch B+ supply.
  3. With a scan tool, monitor the suspect circuits in Body Control Module, Data Display, Inputs:
    • Ignition 0
    • Ignition 1
    • Ignition Accessory
Does the scan tool indicate that the suspect circuits are now active/On?		 Go to Step 9  Go to Step 10 
9 Inspect for poor connections at the ignition switch harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections andConnector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 12 
10
  1. Disconnect the BCM harness connectors.
  2. Test the suspect ignition switch input circuits for a short to ground or an open. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 11 
11 Inspect for poor connections at the BCM harness connectors. 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 14  Go to Step 13 
12 Replace the ignition switch. Refer to Ignition Switch Replacement in Steering Wheel and Column.
Did you complete the replacement?		 Go to Step 14  -
13
IMPORTANT: Perform the programming or setup procedure for the module, if required.
Replace the BCM. Refer to Body Control Module Replacement .Did you complete the replacement?		 Go to Step 14  -
14
  1. Reconnect all components.
  2. Use the scan tool in order to clear DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 Go to Step 2  System OK
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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.