GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC U0073

Circuit Description

The controller area network (CAN) circuits provide a communication network between the electronic brake control module (EBCM), steering wheel position sensor, yaw rate sensor, and the data link connector (DLC).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U0073 CAN Bus Communication

Conditions for Running the DTC

DTC U0073 can be set anytime the ignition switch is in the ON position.

Conditions for Setting the DTC

The EBCM detects a open, high resistance, or short in the CAN circuits.

Action Taken When the DTC Sets
    • The Antilock Brake System (ABS) warning indicator turns ON.
    • The vehicle stability control (VSC) warning indicator turns ON.
    • The VSC and traction control is disabled.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • An open or high resistance in the CAN - high or CAN - low circuits
    • A short between the CAN - high and CAN - low circuits
    • A short to ground in the CAN - high or CAN - low circuits
    • A short to voltage in the CAN - high or CAN - low circuits
    • A steering wheel position sensor malfunction
    • A yaw rate sensor malfunction
    • An internal EBCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. Test the CAN - high and CAN - low circuits for an open or high resistance.

    2.

  2. Test the CAN - high and CAN - low circuits for a short between circuits.

Step

Action

Value(s)

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. Measure the resistance between the CAN bus terminal - high and CAN bus terminal - low of the data link connector (DLC).

Is the resistance within the specified range?

54-69 ohms

Go to Step 3

Go to Step 4

3
  1. Turn OFF the ignition.
  2. Measure the resistance between the CAN - low circuit and the BAT terminal of the DLC.
  3. Measure the resistance between the CAN - high circuit and the BAT terminal of the DLC.

Is the resistance as specified?

1M ohms or Greater

Go to Step 5

Go to Step 6

4

Is the resistance between the CAN bus terminal - high and CAN bus terminal - low of the DLC as specified?

Above 69 ohms

Go to Step 7

Go to Step 8

5
  1. Turn OFF the ignition.
  2. Measure the resistance between the CAN - high circuit and the CG terminal of the DLC.
  3. Measure the resistance between the CAN - low circuit and the CG terminal of the DLC.

Is the resistance as specified?

3k ohms or Greater

Go to next U DTC. Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 9

6
  1. Turn OFF the ignition
  2. Disconnect the electronic brake control module (EBCM) connector.
  3. Measure the resistance between the CAN - high and BAT terminals of the DLC.
  4. Measure the resistance between the CAN - low and BAT terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

1M ohms or Greater

Go to Step 21

Go to Step 10

7

Test the CAN - high and CAN - low circuits for an open or high resistance.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 11

8

Test the CAN - high and CAN - low circuits for a short between circuits.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 12

9
  1. Turn OFF the ignition
  2. Disconnect the EBCM sensor connector.
  3. Measure the resistance between the CAN - high and CG terminals of the DLC.
  4. Measure the resistance between the CAN - low and CG terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

3k ohms or Greater

Go to Step 21

Go to Step 13

10
  1. Turn OFF the ignition
  2. Connect the EBCM connector.
  3. Disconnect the steering wheel position sensor connector.
  4. Measure the resistance between the CAN - high BAT terminals of the DLC.
  5. Measure the resistance between the CAN - low BAT terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

1M ohms or Greater

Go to Step 19

Go to Step 14

11

Are DTCs U0073, U0123, U0124, and U0126 all output?

--

Go to Step 21

Go to Step 19

12
  1. Turn OFF the ignition
  2. Disconnect the EBCM connector.
  3. Measure the resistance between the CAN bus - high and CAN bus - low terminals of the EBCM. Refer to Circuit Testing and Wiring Repairs .

Is the resistance within the specified range?

108-132 ohms

Go to Step 15

Go to Step 21

13
  1. Turn OFF the ignition
  2. Connect the EBCM connector.
  3. Disconnect the steering wheel position sensor connector.
  4. Measure the resistance between the CAN - high and CG terminals of the DLC.
  5. Measure the resistance between the CAN - low and CG terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

3k ohms or Greater

Go to Step 19

Go to Step 16

14
  1. Turn OFF the ignition
  2. Connect the steering wheel position sensor connector.
  3. Disconnect the yaw rate sensor connector.
  4. Measure the resistance between the CAN - high and BAT terminals of the DLC.
  5. Measure the resistance between the CAN - low and BAT terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

1M ohms or Greater

Go to Step 20

Go to Step 17

15
  1. Turn OFF the ignition
  2. Disconnect the steering wheel position sensor connector.
  3. Measure the resistance between the CAN bus - high and CAN bus - low terminals of the steering wheel position sensor. Refer to Circuit Testing and Wiring Repairs .

Is the resistance within the specified range?

108-132 ohms

Go to Step 20

Go to Step 19

16
  1. Turn OFF the ignition
  2. Connect the steering wheel position sensor connector.
  3. Disconnect the yaw rate sensor connector.
  4. Measure the resistance between the CAN - high and CG terminals of the DLC.
  5. Measure the resistance between the CAN - low and CG terminals of the DLC. Refer to Circuit Testing and Wiring Repairs .

Is the resistance as specified?

3k ohms or Greater

Go to Step 20

Go to Step 18

17

Locate and repair the short to B+ in the CAN circuits.

Did you find and correct the condition?

--

Go to Step 22

--

18

Locate and repair the short to ground in the CAN circuits.

Did you find and correct the condition?

--

Go to Step 22

--

19

Replace the steering wheel position sensor. Refer to Steering Wheel Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 22

--

20

Replace the yaw rate sensor. Refer to Vehicle Yaw Sensor Replacement .

Did you complete the replacement?

--

Go to Step 22

--

21

Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

Go to Step 22

--

22
  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