SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1082 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2647: AMBIENT LIGHT SENSOR CIRCUIT LOWTEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Description

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The number(s) below refer to the step number(s) on the diagnostic table.

  1. 3:  This step tests for the proper operation of the circuit in the high voltage range.
  2. 4:  This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
DTC B2647

Step Action Value(s) Yes No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics 
Connector End View Reference: Master Electrical Component List
1 Did you perform the Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Lighting Systems 
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the ambient light sensor parameter in the body control module data list.
Does the scan tool indicate that the ambient light sensor parameter is within the specified range?		 1.5-6.0 V Go to Diagnostic Aids Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the ambient light sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the ambient light sensor parameter.
Does the scan tool indicate that the ambient light sensor parameter is greater than the specified value?		 6.0 V Go to Step 4  Go to Step 5 
4 
  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the signal circuit of the ambient light sensor and the low reference circuit of the ambient light sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the ambient light sensor parameter.
Does the scan tool indicate that the ambient light sensor parameter is less than the specified value?		 1.50 V Go to Step 8  Go to Step 6 
5 Test the signal circuit of the ambient light sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
6 Test the signal circuit of the ambient light sensor for a short to battery positive voltage or 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 7 
7 Test the low reference circuit of the ambient light sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
8 Inspect for a high resistance at the harness connector of the ambient light sensor. 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 a high resistance at the harness connector of the body control module (BCM). 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 ambient light sensor. Refer to Daytime Running Lamps (DRL) Ambient Light Sensor Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11
IMPORTANT: Perform the set up procedure for the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control Systems.
Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?		 - Go to Step 12  -
12
  1. Use the scan tool in order to clear the DTCs.
  2. 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
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.