GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 DTC 🢒 DTC U0100-U0299

Circuit Description

The CAN network allows exchange of information between the Engine Control Module (ECM) and the ABS module.

Conditions for Setting the DTC
    • Ignition ON.
    • No reception of message from EBCM.

Action Taken When the DTC Sets
    • The Malfunction Indicator Lamp (MIL) will illuminate.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the freeze frame and failure records buffers.
    • A history DTC is stored.

Conditions for Clearing the MIL/DTC
    • A history DTC will clear after 40 warm-up cycles without a fault.
    • DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

An Intermittent problem may be caused by a poor connection, rubbed through wire insulation, or wire that is broken inside the insulation. Any circuitry, that is suspected as causing the complaint, should be thoroughly checked for the following conditions.

    • Backed-out terminals
    • Improper mating
    • Broken locks
    • Improperly formed
    • Damaged terminals
    • Poor terminals to wire connections
    • Physical damage to the wiring harness

Step

Action

Yes

No

 

1

Did you perform the Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn the ignition switch to LOCK.
  2. Install the scan tool to the Data Link Connector (DLC).
  3. Turn the ignition switch to ON.

Are any Diagnostic Trouble Codes(DTCs) displayed?

Go to Step 3

System OK

3

Refer to the applicable DTC table. Start with the DTC with the lowest numerical value and move up.

Is the DTC identified as valid trouble code U0121?

Go to Step 4

Go to applicable DTC table

4
  1. Turn the ignition switch to OFF.
  2. Disconnect the Engine Control Module(ECM) and the ABS module.
  3. Check for an open or a short to ground in the wire between the CAN high of ABS module and ECM connector terminal 41.

Is the problem found?

Go to Step 6

Go to Step 5

5

Check for an open or short to ground in the wire between the CAN low of ABS module and ECM connector terminal 22.

Is the problem found?

Go to Step 6

Go to Step 7

6
  1. Change the unshielded twisted pair between ABS module and ECM or repair the connector terminal as needed.
  2. Change the unshielded twisted pair between ABS module and ECM or repair the connector terminal as needed.
  3. Using the scan tool, clear the DTCs.
  4. Start the engine and idle at normal operating temperature.
  5. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?

Go to Step 9

Go to Step 2

7
  1. Replace the ABS module.
  2. Using the scan tool, clear the DTCs.
  3. Start the engine and idle at normal operating temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?

Go to Step 9

Go to Step 8

8
  1. Replace the ECM.
  2. Using the scan tool, clear the DTCs.
  3. Start the engine and idle at normal operating temperature.
  4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?

Go to Step 9

-

9

Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed?

Go to appropriate DTC table

System OK