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Home >> Buick >> 2004 >> Century Base >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Shift Lock Control System >> Diagnostic Information and Procedures >> DTC B2708: Gearshift Unlock Circuit Range/Performance >> Test Description

Test Description

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

  1. 2:  Listen for an audible click when the brake to shift relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
  2. 3:  Verifies that the body control module (BCM) is providing ground to the control circuit of the brake to shift relay.
  3. 4:  Tests if short to battery voltages is present.
  4. 5:  Tests if the brake to shift relay control circuit is open.
  5. 11:  The body control module must be programmed for the vehicle RPO configuration.
DTC B2708

Step Action Yes No
Schematic Reference:  Automatic Transmission Shift Lock Control Schematics  
Connector End View Reference:  Automatic Transmission Shift Lock Control Connector End Views   or  Body Control System Connector End Views 
1 Did you perform the Automatic Transmission Shift Lock Control Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Automatic Transmission Shift Lock Control 
2 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the brake to shift relay ON and OFF.
Does the brake to shift 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 brake to shift relay.
  3. Connect a test lamp between the control circuit of the brake to shift relay and brake to shift relay supply voltage circuit at the connector of the brake to shift relay.
  4. Turn ON the ignition, with the engine OFF
  5. With a scan tool, command the brake to shift relay ON and OFF.
Does the test lamp turn ON and OFF with each command?		 Go to Step 8  Go to Step 4 
4  Does the test lamp remain illuminated? Go to Step 7  Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Connect a test lamp between the control circuit of the brake to shift relay at the body control module (BCM) and battery voltage.
  3. Turn ON the ignition, with the engine OFF
  4. With a scan tool, command the brake to shift relay ON and OFF.
Does the test lamp turn ON and OFF with each command?		 Go to Step 6  Go to Step 9 
6 Repair the open in the brake to shift relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 12  -
7 Test the brake to shift relay control circuit 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 12  Go to Step 9 
8 Inspect for poor connections at the harness connector of the brake to shift 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 12  Go to Step 10 
9 Inspect for poor connections at the harness connector of the body control module. 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 brake to shift relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
Did you complete the replacement?		 Go to Step 12  -
11 
IMPORTANT: Perform the set-up procedure for the body control module (BCM).
Replace the body control module (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
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