No Communication With EBCM

Circuit Description
The Class 2 serial data line allows all of the modules on the line to transmit information to each other as needed. Each module is assigned an ID. All of the information sent out on the line is assigned a priority by which it is received. When the ignition is turned ON, each module begins to send and receive information. Each module on the Class 2 serial data line knows what information the module needs to send out and what information the module should be receiving. What the modules do not know is which module is supposed to send the information. This information is only learned after the module has received the information needed along with the ID of the module that sent the information. This information is then remembered until the ignition switch is turned off.

Diagnostic Aids
^ The following are possible causes:
- An open or short in the Class 2 serial data line.
- An open in the ignition positive voltage circuit.
- An open in the EBCM ground circuit.
- An internal EBCM malfunction.
^ 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.
^ If an intermittent malfunction exists, refer to Testing for Intermittent and Poor Connections see Diagnostic Aids under Diagrams.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This test determines if the scan tool can communicate with any other modules on the Class 2 serial data line.
4. Tests for a short to ground in the ignition positive voltage circuit.
6. Tests the EBCM ground circuit for an open or high resistance.
7. Tests the ignition positive voltage circuit for an open or high resistance.