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HOMESERVICE MANUALSCHEVROLET2001SUBURBAN C1500REPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESBODY CONTROL MODULESDIAGNOSTIC INFORMATION AND PROCEDURESDTC B1398TEST DESCRIPTION
2001 Chevrolet Suburban C1500

Test Description

2001 Chevrolet Suburban C1500SECTION Test Description

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

  1. 2 

    Tests for the proper operation of the circuit in the low voltage range.

  2. 3 

    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. 4 

    Tests for a short to voltage in the 5 volt reference circuit.

DTC B1398

Step Action Value(s) Yes No
Schematic Reference: Body Control System Schematics 
1
  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 (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 2 
2 
  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 less than the specified value?		 0.2 V Go to Step 3  Go to Step 8 
3 
  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the 5 volt reference circuit of the ambient light sensor and the signal 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 greater than the specified value?		 4.7 V Go to Step 4  Go to Step 6 
4 
  1. Disconnect the fused jumper wire.
  2. Measure the voltage between the 5 volt reference circuit of the ambient light sensor and the signal circuit of the ambient light sensor.
Does the voltage measure less than the specified value?		 5.25 V Go to Step 9  Go to Step 5 
5 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 13  Go to Step 10 
6 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 13  Go to Step 7 
7 Test the 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 13  Go to Step 10 
8 Test the 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 13  Go to Step 10 
9 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 13  Go to Step 11 
10 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 13  Go to Step 12 
11 Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement .
Did you complete the replacement?		 - Go to Step 13  -
12
  1. Replace the BCM. Refer to Body Control Module Replacement  in Body Control System.
  2. Program the BCM with the proper calibrations. Refer to Body Control Module (BCM) Programming/RPO Configuration  in Body Control System.
Did you complete the replacement?		 - Go to Step 13  -
13
  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 1  System OK
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.