GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Park Avenue 🢒 Restraints 🢒 SIR 🢒 DTC C1284 or C1285

Circuit Description

The vehicle stability enhancement system (VSES) is activated by the electronic brake control module (EBCM) calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C1284 Lateral Accelerometer Sensor Bias Malfunction
    • DTC C1285 Lateral Accelerometer Sensor Circuit Malfunction

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

C1284

The compensated bias value of the lateral accelerometer is greater than 0.3 grams.

C1285

The lateral accelerometer input voltage is less than 0.15 volts or greater than 4.85 volts for 1 second.

Action Taken When the DTC Sets
    • The EBCM disables the VSES for the duration of the ignition cycle.
    • The driver information center (DIC) displays the Service Stability System message.
    • The antilock brake system (ABS)/traction control system (TCS) remains functional.

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 following conditions can cause this concern:

    • Improper steering alignment
    • Open, short to ground, or short to voltage
    • Internal lateral accelerometer failure
    • EBCM internal failure

Test Description

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

  1. This step tests for the proper operation of the circuit in the low voltage range.

    2.

  2. This step tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.

    3.

  3. This step tests or a short to voltage in the 5-volt reference circuit.

    4.

  4. This step tests the bias voltage of the lateral accelerometer sensor.

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 in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Lateral Accelerometer Input parameter in the VSES data list.

Does the scan tool display that the Lateral Accelerometer Input parameter is within the specified range?

0.15-4.85 V

Go to Step 6

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the lateral accelerometer sensor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Lateral Accelerometer Input parameter.

Does the scan tool display that the Lateral Accelerometer Input parameter is less than the specified value?

0.15 V

Go to Step 4

Go to Step 10

4

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the lateral accelerometer sensor and the signal circuit of the lateral accelerometer sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Lateral Accelerometer Input parameter.

Does the scan tool display that the Lateral Accelerometer Input parameter is greater than the specified value?

4.85 V

Go to Step 5

Go to Step 8

5

  1. Disconnect the fused jumper wire.
  2. Measure the voltage between the 5-volt reference circuit of the lateral accelerometer sensor and the low reference circuit of the lateral accelerometer.

Does the voltage measure less the specified value?

5 V

Go to Step 12

Go to Step 7

6

Does the scan tool display the Lateral Accelerometer Input parameter is within the specified range?

2.3-2.7 V

Go to Diagnostic Aids

Go to Step 11

7

Test the 5-volt reference circuit of the lateral accelerometer sensor 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 16

Go to Step 13

8

Test the 5-volt reference circuit of the lateral accelerometer sensor for the following conditions:

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

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 9

9

Test the signal circuit of the lateral accelerometer sensor for the following conditions:

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

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

Test the signal circuit of the lateral accelerometer sensor 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 16

Go to Step 13

11

    Important: Removing battery voltage or ground from the electronic brake control module (EBCM) will result in the following conditions:

       • Loss of the tire inflation module (TIM) learned tire inflation configuration parameters in the EBCM
       • The EBCM sets DTC C1245.
    When the diagnosis is complete, inspect the tire pressures and perform the TIM reset. Refer to Tire Pressure Monitor Procedure in Tire Pressure Monitoring.

  1. Disconnect the EBCM harness connector.
  2. Install the J 39700 Universal Pinout Box using the J 39700-300 Cable Adapter to the EBCM harness connector only.
  3. Test the low reference circuit of the lateral accelerometer sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

12

Inspect for poor connections at the harness connector of the lateral accelerometer sensor. 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 16

Go to Step 14

13

Inspect for poor connections at the harness connector of the EBCM. 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 16

Go to Step 15

14

Replace the lateral accelerometer sensor. Refer to Lateral Accelerometer Replacement .

Did you complete the replacement?

--

Go to Step 16

--

15

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

Did you complete the replacement?

--

Go to Step 16

--

16
  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