For 1990-2009 cars
Data Link Communications Components
Data Link Connector Schematics

### Circuit Description

The 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 this data is received. When the ignition switch is turned to the ON position, each module begins to send and receive information.

Each module on the serial data line knows what information to send and what information to expect. If the serial data link wire becomes grounded, DTC U1300 sets.

### Conditions for Setting the DTC

DTC U1300 can be set anytime the ignition is in ON. 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.

• | 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.

• | Use the scan tool CLEAR DTCs function.

• | DTC U1300 clears the EBCM 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.

• | All IPC history codes will be cleared after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

### 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 for serial data line diagnosis.

• | Inspect all circuitry suspected of causing the intermittent complaint for the following conditions:

- | Backed-out terminals

- | Improper mating

- | Broken locks

- | Improperly formed terminals

- | Damaged terminals

- | Poor terminal-to-wiring connections

- | Physical damage to the wiring harness

The malfunction may be intermittent. Try performing the tests shown while wiggling the wiring and the connectors. This can often cause the malfunction to appear. PCM and BCM 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 Step 2 | Go to Diagnostic System Check in Antilock Brake System
2 |

1. Disconnect the LH I/P junction block connector C1.
2. Disconnect the EBCM harness connector.
3. Use the J 39200 to measure the resistance between the EBCM harness connector terminal 12 and ground.

Is the measured resistance within the specified value?

OL

(Infinite)

Go to Data Link Communications System Check in Wiring Systems

Go to Step 3

3 | Repair the short to ground in CKT 1807. Is the repair complete? | -- | Go to Diagnostic System Check in Antilock Brake System | --