GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Allure 🢒 Restraints 🢒 SIR 🢒 DTC C0870

Circuit Description

The brake pressure sensor reference voltage is monitored for an over or under voltage condition.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0870 Device Voltage Reference Output {single or 1} Circuit

Conditions for Running the DTC
    • The ignition is ON.
    • The vehicle speed is greater than 40 km/h (25 mph).

Conditions for Setting the DTC

A malfunction is detected if the supply voltage is above 5.6 volts or below 4.4 volts for more than 60 milliseconds.

Action Taken When the DTC Sets
    • A malfunction DTC is set.
    • The ABS, traction control system (TCS) and vehicle stability enhancement system (VSES) are disabled.
    • The ABS, SERVICE VEHICLE SOON and Stability Off lamp indicators are ON.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • Using 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

Possible causes of this DTC are the following conditions:

    • An open in the pressure sensor supply voltage circuit
    • A short to ground in the pressure sensor supply voltage circuit
    • A short to B+ in the pressure sensor supply voltage circuit

Test Description

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

  1. This step tests for specified voltage on the brake pressure signal circuit.

    2.

  2. This step checks to see if the brake pressure signal circuit voltage was below specified voltage.

    3.

  3. This step checks to see if the brake pressure signal circuit voltage was above specified voltage.

    4.

  4. This step tests for a short to ground in the 5-volt reference circuit of the brake pressure sensor.

    5.

  5. This step tests for a short to voltage in the 5-volt reference circuit of the brake pressure sensor.

    6.

  6. This step tests for a high resistance or an open in the ground circuit of the brake pressure sensor.

    7.

  7. This step checks the brake pressure sensor connector for poor connections.

    8.

  8. This step checks the EBCM connector for poor connections.

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 electronic brake control module (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 pin 17 and pin 15 of the J 39700 .

Is the voltage within the specified value?

4.4-5.6 V

Go to Diagnostic Aids

Go to Step 3

3

  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 pin 17 and pin 15 of the J 39700 .

Is the voltage greater than the specified value?

4.4 V

Go to Step 4

Go to Step 5

4

Using the DMM, measure the voltage between pin 17 and pin 15 of the J 39700 .

Is the voltage less than the specified value?

5.6 V

Go to Step 8

Go to Step 6

5

Test the 5-volt reference circuit of the brake pressure sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the 5-volt reference circuit of the brake pressure 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

7

Test the ground circuit of the brake pressure sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

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 12

Go to Step 10

9

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 12

Go to Step 11

10

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

Did you complete the replacement?

--

Go to Step 12

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11

Replace the 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. 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 test.

Does the DTC reset?

--

Go to Step 2

System OK