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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN PASSENGER EXTENDED, 5.0 MREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 919 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2647TEST DESCRIPTION

2001 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 M

Test Description

2001 Chevrolet Chevy Express G2500, Van Passenger Extended, 5.0 MSECTION Test Description

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2001 GMC Yukon XL, 2001 GMC Yukon, 2001 GMC Sierra, 2001 GMC Cab & Chassis Sierra, and 2001 GMC C3500 HD. 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.

3
Tests for the proper operation of the ambient light sensor signal circuit in the low voltage range.
4
Tests for the proper operation of the ambient light sensor signal circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the ambient light sensor signal circuit is shorted to ground.
5
Tests for a short to voltage in the 5 volt reference circuit.
13
After replacement of the BCM you must calibrate the new module for proper operation.

DTC B2647

Step	Action	Value(s)	Yes	No
1	Did you perform the Lighting Systems Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the Ambient Light Sensor parameter in the Body Control Module (BCM) data list . Does the scan tool indicate that the Ambient Light Sensor parameter is within the specified range?	0.2-4.7 V	Go to Diagnostic Aids	Go to Step 3
3	Turn OFF the ignition. Disconnect the ambient light sensor. Turn ON the ignition, with the engine OFF. 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?	0.2 V	Go to Step 4	Go to Step 9
4	Turn OFF the ignition. Connect a 3 amp fused jumper wire between the 5 volt reference circuit of the ambient light sensor and the ambient light sensor signal circuit of the ambient light sensor. Turn ON the ignition, with the engine OFF. 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?	4.7 V	Go to Step 5	Go to Step 7
5	Disconnect the fused jumper wire. Measure the voltage between the 5 volt reference circuit of the ambient light sensor and the ambient light sensor signal circuit of the ambient light sensor. Does the voltage measure less than the specified value?	5.25 V	Go to Step 10	Go to Step 6
6	Test the 5 volt reference circuit of the ambient light sensor 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
7	Test the 5 volt reference circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 8
8	Test the ambient light sensor signal circuit of the ambient light sensor for a short to ground, a high resistance, or an open. 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
9	Test the ambient light sensor signal circuit of the ambient light sensor 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
10	Inspect for poor connections 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 14	Go to Step 12
11	Inspect for poor connections at the harness connector of the 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 14	Go to Step 13
12	Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement . Did you complete the replacement?	-	Go to Step 14	-
13	IMPORTANT: Perform the setup procedure for the body control module. Replace the body control module. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	-	Go to Step 14	-
14	Use the scan tool in order to clear the DTCs. 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.