Circuit Description
The serial data link is a communication line between the PCM, EBCM, and the BFC.
Conditions for Setting the DTC
DTC U1300 can be set anytime the ignition is in RUN. A malfunction exists if CKT 1807 is shorted to ground resulting in no communication to the PCM or any other controller.
Action Taken When the DTC Sets
| • | A malfunction DTC stores. |
| • | The ABS remains functional. |
| • | No action towards the electronic brake control relay is taken. |
| • | No action towards the ABS warning indicator is taken. |
Conditions for Clearing the DTC
| • | The condition for DTC U1300 is no longer present. |
| • | The use of the scan tool CLEAR DTCs function. |
| • | DTC U1300 clears after 100 drive cycles with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition off. |
Diagnostic Aids
| • | Perform the Powertrain OBD System Check before beginning this DTC table. This eliminates the PCM as a possible source of the malfunction. |
| • | The following conditions may cause an intermittent malfunction: |
| • | A poor connection |
| • | Rubbed-through wire insulation |
| • | A broken wire inside the insulation within the serial data line. Refer to Data Link Communications System Check in Wiring Systems for serial data line diagnosis. |
| • | The use of the enhanced diagnostic function of the scan tool to check the frequency of the malfunction. Refer to Scan Tool Diagnostics . |
| • | Check all circuitry suspected of causing the intermittent complaint for the following conditions: |
| • | Check for backed-out terminals. |
| • | Check for improper mating. |
| • | Check for broken locks. |
| • | Check for improperly formed terminals. |
| • | Check for damaged terminals. |
| • | Check for poor terminal to wiring connections. |
| • | Check for physical damage to the wiring harness. |
The scan tool Serial Data Link (SDL) monitor used in this diagnostic is within the body portion of the scan tool. This requires exiting from the chassis portion of the scan tool to the main menu and entering into the body portion of the scan tool and selecting SDL MONITOR.
With the SDL monitor (ABS to Instrument Cluster Mode), any message that is being transmitted on the serial data link can be observed.
The malfunction may be intermittent. Try performing the tests shown while "wiggling" wiring and connectors, this can often cause the malfunction to appear. PCM and BFC DTCs will likely be set along with DTC U1300.
DTC U1300 will only be able to be read as a history code since the scan tool uses the same serial data circuit. If CKT 1807 is shorted to ground, no communication with the scan tool will be possible.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 |
Is the measured resistance within the specified value? | OL (Infinite) | Go to Data Link Communications Schematic References in Wiring Systems | |
3 | Repair the short to ground in CKT 1807. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
