GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0870

Circuit Description

The electronic brake control module (EBCM) supplies voltage to the brake pressure sensor, steering angle sensor, and yaw rate/lateral accelerometer sensor. This voltage is monitored by the EBCM for an over or under voltage condition.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0870 Device Voltage Reference Output Circuit

Conditions for Running the DTC
    • The ignition is ON.
    • Ignition voltage is greater than 8 volts.

Conditions for Setting the DTC

One of the follow conditions exists for 0.1 seconds:

    • The sensor supply voltage is greater than 5.2 volts.
    • The sensor supply voltage is less than 4.8 volts.

Action Taken When the DTC Sets
    • The EBCM disables the VSES for the duration of the ignition cycle.
    • ACC braking function disabled.
    • TCS is degraded.
    • The Traction Control and Active Handling indicator turns ON.
    • The DIC displays the Service Active Handling 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 electronic brake control module (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:

    • The sensor supply circuit is open, shorted to ground, or shorted to battery.
    • Internal sensor malfunction.
    • Internal EBCM malfunction.

Test Description

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

  1. Tests for a short at the brake pressure sensor.

    2.

  2. Tests for a short at the steering wheel position sensor.

    3.

  3. Tests for a short at the yaw rate/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

2

Test the 5-volt reference circuit from the electronic brake control module (EBCM) 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 16

Go to Step 3

3

Test the 5-volt reference circuit from the EBCM for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the EBCM.
  3. Install the J 39700 Universal Pinout Box with the J 39700-530 Cable Adapter between the EBCM and the EBCM harness connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Using the DMM, measure the voltage between the 5-volt reference circuit and ground.

Is the voltage within the specified value?

4.8-5.2 V

Go to Diagnostic Aids

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the brake pressure sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Using the DMM, measure the voltage between the 5-volt reference circuit and ground.

Is the voltage within the specified value?

4.8-5.2 V

Go to Step 8

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the steering wheel position sensor connector
  3. Turn ON the ignition, with the engine OFF.
  4. Using the DMM, measure the voltage between the 5-volt reference circuit and ground.

Is the voltage within the specified value?

4.8-5.2 V

Go to Step 9

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the yaw rate/lateral accelerometer sensor connector
  3. Turn ON the ignition, with the engine OFF.
  4. Using the DMM, measure the voltage between the 5-volt reference circuit and ground.

Is the voltage within the specified value?

4.8-5.2 V

Go to Step 10

Go to Step 11

8

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

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

9

Inspect for poor connections at the harness connector of the steering wheel position sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

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

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

11

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

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

12

Replace the brake pressure sensor. Refer to Brake Pressure Modulator Valve Pressure Sensor Replacement .

Did you complete the repair?

--

Go to Step 16

--

13

Replace the steering wheel position sensor. Refer to Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement .

Did you complete the repair?

--

Go to Step 16

--

14

Replace the yaw rate/lateral accelerometer sensor. Refer to Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement .

Did you complete the repair?

--

Go to Step 16

--

15

Replace the EBCM. Refer to Control Module References 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