GM Service Manual Online
For 1990-2009 cars only

Object Number: 307942  Size: MF
ABS Components
Antilock Brake System Schematics
Handling Electrostatic Discharge Sensitive Parts Notice
Data Link Connector Schematics
Power Distribution Schematics
Antilock Brake System Schematics

Circuit Description

The EBTCM Diagnostic System Check is an organized approach to identify problems associated with the EBTCM. This check must be the starting point for any EBTCM complaint, and will direct you to the next logical step in diagnosing the complaint. The EBTCM is a very reliable component and is not likely the cause of the malfunction. Most system complaints are linked to faulty wiring, connectors, and occasionally to components. Understanding the ABS/ETS (Antilock Brake System/Enhanced Traction Control System which is standard for this vehicle) system and using the tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.

The Diagnostic system check directs the service technician to the next logical step in diagnosing the complaint. The following connectors/terminals will give you a better understanding on what each terminal performs.

    • Connector C1 terminal A1 exchanges serial data to and from the EBTCM.
    • Connector C1 terminal A9 supplies the switched ignition voltage to the EBTCM.
    • Connector C1 terminal B12 supplies the battery voltage to the EBTCM.
    • Connector C2 terminal C supplies the switched battery voltage to the EBTCM.
    • Connector C2 terminal D provides the ground for the EBTCM.

Diagnostic Aids

    • An intermittent failure in the electronic system may be very difficult to detect and to accurately diagnose. The EBTCM tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed in order to repeat a malfunction. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent malfunction. Faulty electrical connections or wiring causes most intermitting problems. When an intermittent condition is suspected, check the suspected circuits for the following conditions:
       - Poor mating of connector halves or backed out terminals
       - Improperly formed or damaged terminals
       - Wiring damage, especially at vehicle attachment points
       - Poor wire to terminal connections
       - Dirty or corroded terminals
       - Damage to connector bodies
    • If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Refer to General Electrical Diagnosis in Wiring System.

ABS Diagnostic System Check

Step

Action

Value(s)

Yes

No

1

  1. Plug a scan tool into the Diagnostic Link Connector (DLC).
  2. Turn the ignition switch from the OFF to ON position, Do not start engine.

Does the scan tool communicate with the EBTCM?

--

Go to Step 4

Go to Step 2

2

Does the scan tool communicate with other modules on the Class 2 serial data line, such as the PCM?

--

Go to Step 3

Go to (Link no longer avaliable) for Diagnosis

3

  1. Disconnect the 24-way EBTCM connector  C1.
  2. Disconnect the bus bar from Splice Pack  SP205.
  3. Using (Link no longer avaliable) , measure the resistance between EBTCM connector  C1 terminal  A1 and Splice Pack  SP205 terminal A.

Is the resistance measured within the specified range?

0-2 ohms

Go to Step 4

Go to (Link no longer avaliable) in Wiring Systems

4

  1. Carefully road test the vehicle for several minutes over different road surfaces and with several turns above 24 km/h (15 mph).
  2. Connect the scan tool into the Diagnostic Link Connector (DLC).
  3. With the scan tool read ABS/ETS DTCs.

Are there any current Diagnostic Trouble Codes?

--

Go to (Link no longer avaliable) for the Applicable DTC

Go to Step 5

5

  1. Remove the scan tool from the DLC.
  2. Turn the ignition switch from the OFF to ON position, engine off.

Does the ABS Indicator turn on then turn off after several seconds?

--

Go to Step 6

Go to Step 7

6

Turn the ignition switch from the OFF to ON position, engine off.

Does the ETS/TRAC Off Indicator turn on then turn off after several seconds?

--

Go to Step 9

Go to Step 8

7

Does the ABS Indicator stay on?

--

Go to (Link no longer avaliable)

Go to (Link no longer avaliable)

8

Does the ETS/TRAC Off Indicator stay on?

--

Go to (Link no longer avaliable)

Go to (Link no longer avaliable)

9

Are there any history DTCs?

--

Go to Step 10

System OK

10

  1. Refer to the appropriate DTC table for the history DTC.
  2. Read the diagnostic aids and the conditions for setting the DTC.
  3. Unplug the scan tool from the DLC if not already removed.
  4. Turn the ignition switch from the OFF to ON position.
  5. Carefully drive the vehicle above 24 Km/h (15 mph) for several minutes.
  6. Leave the vehicle running and plug the scan tool into the DLC.
  7. With the scan tool read ABS/ETS DTCs.

Did the history DTC set as a current DTC while the vehicle was being driven?

--

Go to (Link no longer avaliable) for the Applicable DTC

System OK