GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2004 🢒 VUE - FWD 🢒 Body 🢒 Data Link Communications 🢒 DTC U0073

Circuit Description

The engine control module (ECM), electronic brake traction control module (EBTCM) and transmission control module (TCM) if applicable, communicate via a controller area network (CAN) serial data bus. The CAN serial data bus transmits over two wires at speeds high enough to ensure that the required real-time response is maintained. Modules connected to the CAN serial data circuits monitor communications. During normal vehicle operation, information and commands are exchanged among modules. A no communication condition may result from a short to voltage, short to ground, or short between the CAN high and low circuits.

Conditions for Running the DTC
    • Voltage supplied to the modules are in the normal voltage range.
    •  The vehicle power mode requires serial communication to occur.

Conditions for Setting the DTC

A no communication condition is detected on CAN serial data circuits.

Action Taken When the DTC Sets

A module may use a default value for a parameter that it expected to receive via serial data.

Conditions for Clearing the MIL/DTC
    • A current DTC and MIL clear when the malfunction is no longer present.
    • A history DTC clears when requested by the scan tool or when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

The modules communicating on the CAN serial data circuits are wired parallel to each other. An open in the CAN circuits for one module will not affect other modules. A short to ground or short to voltage on either wire affects all modules no matter where the failure occurs.

Test Description

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

  1. This test isolates a shorted TCM, ECM, or EBTCM. By reading the signal from the ECM after the wiring is tested, without a TCM connected, an ECM signal generating problem can be diagnosed. When the CAN circuits are open between two components, both components generate a 30,000 to 40,000 hertz signal. When the system is not open, the frequency is 3,000 to 3,500 hertz.

Step

Action

Values

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Data Link Communications Connector End Views

1
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

2

Important: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use DMM MIN/MAX function to compare intermittent conditions.

  1. Turn OFF the ignition.
  2. Disconnect the ECM, TCM if applicable, and EBTCM harness connectors which contain CAN circuits.
  3. Test the CAN serial data circuits for a short to ground, short to voltage, or a short between the CAN High and CAN Low circuits. Refer to the following in Wiring Systems:

Did you find and correct the condition?

 

Go to Step 11

Go to Step 3

3

Important: If the vehicle is not equipped with a TCM, answer YES to this step.

  1. Turn OFF the ignition.
  2. Reconnect the TCM, if equipped.
  3. Clear any DTCs in memory.
  4. Start the engine.
  5. Measure the frequency across the CAN circuits in the harness with a DMM.

Does the frequency measure more than the specified value?

35,000 Hz

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition.
  2. Reconnect the EBTCM, if equipped.
  3. Clear any DTCs in memory.
  4. Start the engine.
  5. Measure the frequency across the CAN circuits in the harness with a DMM.

Does the frequency measure more than the specified value?

35,000 Hz

Go to Step 5

Go to Step 7

5

Inspect for an intermittent or poor connection at the ECM. 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 11

Go to Step 8

6

Inspect for an intermittent or poor connection at the TCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you fine and correct the condition?

 

Go to Step 11

Go to Step 9

7

Inspect for an intermittent or poor connection at the EBTCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you fine and correct the condition?

 

Go to Step 11

Go to Step 10

8

Important: Perform the module setup procedure, if required.

Replace the ECM (L61). Refer to Engine Control Module Replacement in Engine Controls - 2.2L (L61).

Did you complete the replacement?

 

Go to Step 11

--

9

Important: Perform the module setup procedure, if required.

Replace the TCM (5AT). Refer to Powertrain Control Module Replacement in Automatic Transmission - (5AT).

Did you complete the replacement?

 

Go to Step 11

--

10

Important: Perform the module setup procedure, if required.

Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brakes.

Did you complete the replacement?

 

Go to Step 11

--

11
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 12

12

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK