The UART serial data link allows information to be exchanged from module to module as needed. This is done by the PCM, the PCM requests and sends all the information that is transmitted on the UART line. When a scan tool is connected to the UART line it takes over for the PCM and sends and requests the needed information.
• | 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 Communications with EBTCM diagnostic table will diagnose a malfunction with the power or ground circuits and the UART circuit to the EBTCM only. For diagnosis of the entire UART serial data circuit, refer to Data Link Communications System Check in Data Link Communications. |
• | Thoroughly inspect the wiring and the connectors. Failure to carefully and fully inspect the wiring and the connectors can result in misdiagnosis. Misdiagnosis may cause replacement of parts without repairing the malfunction. |
• | If an intermittent malfunction exists, refer to General Electrical Diagnosis in Wiring Systems. |
Step | Action | Value(s) | Yes | No |
---|---|---|---|---|
DEFINITION: Scan tool can not communicate with the EBTCM. | ||||
1 | Was the Diagnostic System Check performed? | -- | ||
2 | Turn the Ignition switch to the RUN position with the engine off. Can the scan tool communicate with other modules on the UART serial data line, such as the PCM? | -- | Go to Data Link Communications System Check in Data Link Communications | |
3 | Inspect the 10A A/C CLU / ABS IGN fuse 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 1239 for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
9 | Repair CKT 251 or G205 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 1239 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 800 for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- |