GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2007 🢒 Terraza Ext. 🢒 Brakes 🢒 Park Brake 🢒 DTC C0186 or C0187

Circuit Description

The electronic brake control module (EBCM) uses the lateral accelerometer signal to determine the lateral forces acting on a vehicle during a turn or a skid. The EBCM uses the signal from the lateral accelerometer as one of the inputs to operate the vehicle stability enhancement system (VSES).

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C0186 Lateral Accelerometer Circuit
    • DTC C0187 Lateral Accelerometer Circuit Range/Performance

Conditions for Running the DTC

C0186

Ignition voltage is greater than 8 volts.

C0187

    • Ignition voltage is greater than 8 volts.
    • No yaw rate DTCs are present.
    • Vehicle yaw rate is centered.

Conditions for Setting the DTC

C0186

Lateral accelerometer signal voltage is less than 0.18 volt or above 4.84 volts.

C0187

The EBCM will set the DTC when one or more of the following conditions have occurred:

    • The lateral acceleration signal changes to rapidly based on vehicle dynamics.
    • The internal calibration in the lateral accelerometer is out of range.
    • The lateral accelerometer has failed and internal self check test.

Action Taken When the DTC Sets

If equipped, the following actions will occur:

    • The EBCM disables VSES for the duration of the ignition cycle.
    • The driver information center (DIC) displays the Service Stability System message.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
    • The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

The lateral accelerometer is packaged with the yaw rate sensor as a single component.

Test Description

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

  1. This step tests for the proper voltage output on the 5-volt reference circuit and the proper operation of the signal circuit.

    2.

  2. This step tests for possible low 5-volt reference output or a problem with the signal circuit.

    3.

  3. This step tests for a short to voltage on the 5-volt reference circuit. If a short to voltage exists, other DTCs may be set for the vehicle stability system.

    4.

  4. This step tests for a problem with the low reference circuit. If a short to voltage exists, other DTCs may be set for the vehicle stability system.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn OFF the ignition.
  2. Disconnect the yaw and lateral acceleration sensor harness connector.
  3. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the yaw and lateral acceleration sensor and the signal circuit of the yaw and lateral acceleration sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. With the scan tool, observe the lateral acceleration signal voltage.

Does the scan tool indicate that the lateral acceleration signal parameter is in between the specified voltage range?

4.5-5.5 V

Go to Step 8

Go to Step 3

3

With the 3-amp fused jumper wire still connected, does the scan tool indicate that the lateral acceleration sensor parameter is below the specified voltage value?

4.5 V

Go to Step 5

Go to Step 4

4

Test the 5-volt reference circuit of the yaw and lateral acceleration sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

5

Test the 5-volt reference circuit of the yaw and lateral acceleration sensor for the following conditions:

    • An open
    • A short to ground
    • A high resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 6

6

Test the lateral accelerometer signal circuit for the following conditions:

    • An open
    • A short to ground
    • A high resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

7

Test the lateral accelerometer signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

8

Test the low reference circuit of the yaw and lateral acceleration sensor for the following conditions:

    • An open
    • A short to voltage
    • A high resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9

Inspect for poor connections at the harness connector of the yaw and lateral acceleration sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

10

Replace the yaw and lateral acceleration sensor. Refer to Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the electronic brake control module (EBCM). Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

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12
  1. Clear the DTCs using the scan tool.
  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