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Test Description

WARNING: This page is about a different car, the 2004 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 3:  Tests for the proper operation of the circuit in the low voltage range.
  2. 4:  Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
  3. 5:  Tests for a short to voltage in the 5-volt reference circuit.
  4. 6:  Tests for a high resistance or an open in the low reference circuit.
DTC B2620

Step Action Value(s) Yes No
Schematic Reference: Interior Lights Dimming Schematics 
Connector End View Reference: Lighting Systems Connector End Views  or Body Control System Connector End Views in Body Control System.
1 Did you perform the Lighting Systems 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 the scan tool, observe the Dimming Input data parameter in the Body Control Module Data List.
Does the scan tool indicate that the Dimming Input data parameter is within the specified range?		 4.5-5.5 V Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the headlamp switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Dimming Input data parameter.
Does the scan tool indicate that the Dimming Input data parameter is less than the specified value?		 4.5 V Go to Step 4  Go to Step 10 
4 
  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the 5-volt reference circuit of the I/P dimmer/headlamp switch and the signal circuit of the I/P dimmer/headlamp switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Dimming Input data parameter.
Does the scan tool indicate that the Dimming Input data parameter is greater than the specified value?		 4.86 V Go to Step 5  Go to Step 8 
5 
  1. Disconnect the fused jumper wire.
  2. Measure the voltage between the 5-volt reference circuit of the I/P dimmer/headlamp switch and the low reference circuit of the I/P dimmer/headlamp switch.
Does the voltage measure less than the specified value?		 5.15 V Go to Step 6  Go to Step 7 
6 
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) in Engine Electrical.
  3. Measure the resistance from the low reference circuit of the I/P dimmer/headlamp switch to a good ground.
Does the resistance measure less than the specified value?		 5 Ω Go to Step 12  Go to Step 11 
7 Test the 5-volt reference circuit of the I/P dimmer/headlamp switch 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 16  Go to Step 13 
8 Test the 5-volt reference circuit of the I/P dimmer/headlamp switch 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 16  Go to Step 9 
9 Test the signal circuit of the I/P dimmer/headlamp switch 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 16  Go to Step 13 
10 Test the signal circuit of the I/P dimmer/headlamp switch 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 16  Go to Step 13 
11
  1. Disconnect the body control module.
  2. Test the low reference circuit of the I/P dimmer/headlamp switch for 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 16  Go to Step 13 
12 Inspect for poor connections at the harness connector of the I/P dimmer/headlamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 14 
13 Inspect for poor connections at the harness connector of the body control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 15 
14 Replace the headlamp switch. Refer to Headlamp Switch Replacement .
Did you complete the replacement?		 - Go to Step 16  -
15
IMPORTANT: Perform the setup procedure for the body control module (BCM).
Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?		 - Go to Step 16  -
16
  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
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