Circuit Description
The UART serial data link allows information to be exchanged from module to module as needed. This is performed when 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, the scan tool takes over for the PCM and sends and requests the needed information.
Diagnostic Aids
| • | 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. |
| • | An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation. |
| • | If an intermittent malfunction exists, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
DEFINITION: The scan tool will not communicate with the EBCM/EBTCM. | ||||
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Step 2 | |
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 Step 3 | Go to Data Link Communications System Check in Data Link Communications |
3 | Inspect the ABS Fuse in the IP fuse block. Is the fuse OK? | -- | Go to Step 4 | Go to Step 8 |
4 | Inspect the ABS MAIN Fuse in the engine compartment fuse block. Is the fuse OK? | -- | Go to Step 10 | Go to Step 5 |
5 |
Is the resistance within the specified range? | OL (infinite) | Go to Step 6 | Go to Step 7 |
6 | Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the replacement complete? | -- | -- | |
7 | Repair a short to ground CKT 242. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
8 |
Is the resistance within the specified range? | OL (infinite) | Go to Step 6 | Go to Step 9 |
9 | Repair a short to ground CKT 441. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
10 |
Is the voltage within the specified range? | Battery Voltage | Go to Step 11 | Go to Wiring Repairs in Wiring Systems |
11 | Use the J 39200 in order measure the voltage at the ABS MAIN Fuse by probing between the fuse test terminals and the vehicle ground. Is the voltage within the specified range? | Battery Voltage | Go to Step 12 | Go to Wiring Repairs in Wiring Systems |
12 |
Is the resistance less than the specified value for both measurements? | 2 ohms | Go to Step 14 | Go to Step 13 |
13 | Repair an open or high resistance in CKT 1451 or G106. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
14 |
Is the voltage within the specified range? | Battery Voltage | Go to Step 16 | Go to Step 15 |
15 | Repair an open or high resistance in CKT 441. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
16 | Use the J 39200 in order to measure the voltage between the J 38716 terminal 35 and terminal 1. Is the voltage within the specified range? | Battery Voltage | Go to Step 6 | Go to Step 17 |
17 | Repair an open in CKT 242. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
