GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Park Avenue 🢒 Restraints 🢒 SIR 🢒 DTC B0803

Circuit Description

The body control module (BCM) supplies voltage to the automatic transmission shift lock control output when the following conditions occur:

    • The ignition switch is in RUN.
    • The transaxle is in the PARK position.

While the brake pedal is pressed, the following functions occur:

    • The stoplamp/automatic transmission shift lock control switch opens the automatic transmission shift lock control circuit.
    • The shift automatic transmission shift lock control solenoid is disabled.

The BCM monitors the output. The BCM determines the actual voltage of the automatic transmission shift lock control circuit every 0.3 seconds.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0803 Transmission Shift Mode Indicator Circuit High

Conditions for Setting the DTC
    • The BCM detects a short to voltage in automatic transmission shift lock control circuit.
    • The condition is present for more than 0.1 second.

Action Taken When the DTC Sets
    • DTC B0803 stores in the BCM memory.
    • No driver warning message displays.

Conditions for Clearing the DTC
    • The BCM no longer detects a short to voltage.
    • A history DTC clears after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.

Test Description

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

  1. Listen for an audible click when the automatic transmission shift lock control solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.

    2.

  2. Verifies that the BCM is providing voltage to the automatic transmission shift lock control solenoid.

    3.

  3. Tests if voltage is constantly being applied to the automatic transmission shift lock control solenoid.

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 Output ON and OFF.

Does the automatic transmission (A/T) shift lock control solenoid turn ON and OFF with each command?

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 A/T shift lock control switch.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the park neutral position switch park signal circuit with a test lamp connected to a good ground.
  5. With a scan tool, command the Brake to Shift Output ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 4

Go to Step 6

4

  1. Turn OFF the ignition.
  2. Reconnect the A/T shift lock control switch.
  3. Disconnect the A/T shift lock control solenoid.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the A/T shift lock control solenoid supply voltage circuit with a test lamp connected to a good ground.
  6. With a scan tool, command the Brake to Shift Output 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 10

Go to Step 7

6

Test the park neutral position switch park signal 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 13

Go to Step 8

7

Test for a open in the A/T shift lock control solenoid supply circuit. 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 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

9
  1. Inspect for poor connections at the harness connector of the A/T shift lock control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Inspect for proper adjustment of the A/T shift lock control switch. Refer to Stop Lamp Switch Adjustment in Lighting Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

10

Repair the short to battery voltage in the A/T shift lock control solenoid supply circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the A/T shift lock control switch. Refer to Stop Lamp Switch Replacement in Lighting Systems.

Did you complete the replacement?

Go to Step 13

--

12

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