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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 740 (HORN SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2527TEST DESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic

Test Description

1999 GMC Forward Control 5.7 R, AutomaticSECTION Test Description
WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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. 2:  Listen for an audible click when the horn relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
  2. 3:  Tests for voltage at the coil side of the horn relay.
  3. 4:  Verifies that the body control module (BCM) is providing ground to the horn relay.
  4. 5:  Tests if ground is constantly being applied to the horn relay.
DTC B2527

Step Action Yes No
Schematic Reference: Horns Schematics 
1 Did you perform the Horns Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Horns 
2 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the horn relay ON and OFF.
Does the horn relay turn ON and OFF with each command?		 Go to Diagnostic Aids Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the horn relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the horn relay coil with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 10 
4 
  1. Connect a test lamp between the horn relay control circuit and the battery positive voltage circuit of the horn relay coil.
  2. With a scan tool, command the horn relay ON and OFF.
Does the test lamp turn ON and OFF with each command?		 Go to Step 8  Go to Step 5 
5  Does the test lamp remain illuminated with each command? Go to Step 7  Go to Step 6 
6 Test the horn relay control circuit for 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 9 
7 Test the horn relay control circuit 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 13  Go to Step 9 
8 Inspect for poor connections at the horn relay. 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 
9 Inspect for poor connections 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 13  Go to Step 12 
10 Repair the battery positive voltage circuit of the horn relay coil. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
11 Replace the horn relay.
Did you complete the replacement?		 Go to Step 13  -
12
IMPORTANT: Perform the BCM programming procedure when replacing the BCM.
Replace the BCM. Refer to Body Control Module Replacement 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 2  System OK
RENDER: 1.0x

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