Circuit Description
The UART serial data line allows information to be exchanged from module to module as needed. This is done by the PCM, the PCM requests and sends the information that is transmitted on the UART line.
Conditions for Setting the DTC
A check takes place in the EBTCM as to whether a message is received by the EBTCM from the PCM every 100 milliseconds. DTC U1304 can be set anytime the ignition is in the RUN position and the EBTCM does not receive a message from the PCM in over 5.6 seconds.
Action Taken When the DTC Sets
| • | A malfunction DTC stores. |
| • | The TCS is disabled. |
| • | The amber TCS indicator is turned on. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used. |
| • | 100 ignition cycles pass with no DTC(s) detected. |
Diagnostic Aids
| • | Perform a thorough inspection of the wiring and the connectors. 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 Testing for Electrical Intermittents in Wiring Systems for further diagnosis. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
This step checks for a short to ground in circuit 800.
-
This step checks for a short to battery voltage in circuit 800.
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This step checks for an open in circuit 800.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS in Antilock Brake System |
Is the resistance within the range specified in the value(s) column? | OL (infinite) | Go to Step 4 | Go to Step 3 | |
3 | Repair CKT 800 for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
Is the voltage within the range specified in the value(s) column? | B+ | Go to Step 5 | Go to Step 6 | |
5 | Repair CKT 800 for a short to battery voltage. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
Is the resistance within the range specified in the values column? | 0-2 ohms | Go to Step 8 | Go to Step 7 | |
7 | Repair CKT 800 for an open. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
8 | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the replacement complete? | -- | -- |
