Circuit Description
The ABS Diagnostic System Check is an organized approach to identify problems associated with the EBCM. This check must be the starting point for any EBCM complaint, and will direct you to the next logical step in diagnosing the complaint. The EBCM 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 system and using the tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Lack of communication may be due to a partial malfunction of the Class 2 or UART serial data circuit or due to a total malfunction of the Class 2 or UART serial data circuit. The specified procedure will determine the particular condition.
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The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Step | Action | Yes | No | ||||
|---|---|---|---|---|---|---|---|
1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up In Data Link Communications | ||||
Turn ON the ignition, with the engine OFF. Attempt to establish communication with the following control module. Electronic brake control module (EBCM). Does the scan tool communicate with the control module? | Go to Step 3 | Go to Scan Tool Does Not Communicate with UART Data Line In Data Link Communications | |||||
3 | Turn ON the ignition, with the engine OFF. Attempt to establish communication with the following control module. Powertrain control module. Does the scan tool communicate with the control module? | Go to Step 4 | Go to Scan Tool Does Not Communicate with Class 2 Device In Data Link Communications | ||||
4 | Select the display DTCs function on the scan tool for the following control modules:
Does the scan tool display any DTCs? | Go to Step 5 | |||||
5 | Does the scan tool display any DTCs which begin with a U (i.e. DTC U1001, U1254, U1304)? | Go to Scan Tool Does Not Communicate with Class 2 Device or Scan Tool Does Not Communicate with UART Data Line in Data Link Communications | Go to Step 6 | ||||
Does the scan tool display any DTCs which begin with a P (i.e. DTC P1571, P1573, P1689)? | Go to Diagnostic Trouble Code (DTC) List in Engine Controls | Go to Diagnostic Trouble Code (DTC) List For The Applicable DTC |
