GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Century 🢒 DTC 🢒 DTC B2707

Circuit Description

The body control module (BCM) controls the brake to shift relay control circuit and monitors the voltage of the control circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC: DTC B2707 Gearshift Unlock Circuit Low

Conditions for Running the DTC

The ignition is in the ON position.

Conditions for Setting the DTC
    • The BCM detects the brake to shift relay control circuit voltage is at or below 1.5 volts in the OFF state.
    • The condition above must be present for more than 0.3 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B2707 in memory.

Conditions for Clearing the DTC
    • A current DTC B2707 will clear if the short to ground or open in the brake to shift relay control circuit is no longer detected by the BCM or after one ignition cycle.
    • A history DTC B2707 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • A scan tool may be used to clear the DTC.

Diagnostic Aids
    • If DTC B2707 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to ground or open in the brake to shift relay control circuit.
       - The brake to shift relay is intermittently shorted to ground internally.
       - The BCM is intermittently shorted to ground internally.

Test Description

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

  1. 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.

  2. Tests for voltage at the brake to shift relay.

    3.

  3. Verifies that the BCM is providing ground to the control circuit of the brake to shift relay.

    4.

  4. Tests if ground is constantly being applied to the brake to shift relay control circuit.

    5.

  5. The body control module must be programmed for the vehicle RPO configuration.

Step

Action

Yes

No

Schematic Reference: Shift Lock Control Schematics

Connector End View Reference: Shift Lock Control Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

1

Did you perform the Diagnostic System Check-Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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 brake to shift relay supply voltage circuit at the connector of the brake to shift relay and a good ground.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

  1. Turn OFF the ignition.
  2. 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.
  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 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 brake to shift 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 brake to shift 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 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 13

Go to Step 11

9

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

10

Repair the open in the ignition 1 voltage circuit of the brake to shift relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the brake to shift relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the set-up procedure for the body control module (BCM).

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

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