Circuit Description
The Class 2 serial data line allows all the modules on the line to transmit information to each other as needed. Each module is assigned an ID and all the information sent out on the line is assigned a priority by which it is received. When the ignition switch is turned to the run position each module begins to send and receive information. Each module on the Class 2 serial data line knows what information it needs to send out and what information it should be receiving. What the modules do not know is which module is supposed to send them the information. This information is only learned after the module has received the information it needs 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
| • | It is very important to start with the ABS Diagnostic System Check before performing the No Communications with EBTCM diagnosis. The ABS Diagnostic System Check will direct you to the Data Link Communications Diagnostic System Check in Data Link Communications to diagnose a malfunction that effects the entire serial data circuit. The No Communication with EBTCM diagnostic table will diagnose a malfunction with the power and ground circuits and the Class 2 circuit to the EBTCM only. For diagnosis of the entire Class 2 serial data circuit, refer to Diagnostic System Check - Data Link Communications in Data Link Communications. |
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. |
| • | Thoroughly inspect any circuitry that may be causing the complaint for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal-to-wiring connections |
| - | Physical damage to the wiring harness |
| • | The following conditions may cause an intermittent malfunction: |
| - | A poor connection |
| - | Rubbed-through wire insulation |
| - | A broken wire inside the insulation |
| • | If an intermittent malfunction exists refer to General Electrical Diagnosis in Wiring Systems for further diagnosis. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: Scan tool can not communicate with the EBTCM. | ||||
1 | Was the ABS Diagnostic System Check performed? | -- | ||
2 | Turn the Ignition switch to the ON position with the engine off. Can the scan tool communicate with other modules on the Class 2 serial data line, such as the PCM? | -- | Go to Diagnostic System Check - Data Link Communications in Data Link Communications | |
3 | Inspect the 10A Trans / ABS fuse 26 in the Underhood Accessory Wiring Junction Block. Is the fuse OK? | -- | ||
4 |
Is the voltage within the range specified within the value(s) column? | Battery Volts | Go to Power Distribution Schematics in Wiring Systems | |
5 |
Is the resistance within the range specified in the value(s) column? | 0 - 5ohms | ||
6 |
Is the fuse OK? | -- | ||
7 |
Is the resistance within the range specified in the value(s) column? | OL (infinite) | ||
8 | Repair CKT 1039 for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
9 | Repair CKT 251 or G201 for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
10 |
Is the voltage within the range specified in the value(s) column? | Battery Volts | ||
11 | Repair CKT 1039 for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
12 | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the replacement complete? | -- | -- | |
13 |
Is the resistance within the range specified in the values column? | 0-5ohms | ||
14 | Repair CKT 1122 for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
