Data Link Connector Diagnosis. Cadillac Concours 1996

For 1990-2009 cars
Engine Controls Components
PCM Power and Grounds
OBD II Symbol Description Notice
ESD Notice

### Circuit Description

The Data Link Connector check is used to identify the cause of an inoperative scan tool. Possible faults include scan tool non-power up and lack of communication between the scan tool and the PCM. The DLC supplies power to the scan tool through CKT 1740 to terminal 16. The ground to the scan tool is supplied through CKT 51 to terminal 5. The serial data (communication) is supplied to the scan tool through CKT 1807 to terminal 2.

### Diagnostic Aids

Perform the A Powertrain On Board Diagnostic (OBD) System Check before performing this chart to help prevent miss-diagnosis.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Checking the voltage and ground supply to the scan tool.

2. Checking if the fault is power or ground circuit related.

3. Terminal 4 of the DLC connector is the ground circuit for scan tool data communications and terminal 5 is the power ground circuit for the scan tool.

4. If communication is present between the scan tool and PCM then the fault is not present or was poor terminal contact at the DLC connector.

5. Checking if the fault is vehicle or scan tool related.

6. If On-Boards do not function there may be a short to ground on CKT 1807 anywhere on the circuit or one of the control modules connected to Class 2 may be faulty. Refer to Section 8 to diagnose the serial data line.

7. Due to the multiple connections to serial data, if no DTCs are present the fault should be between the DLC and the splice.

#### Data Link Connector (DLC) Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Powertrain OBD System Check

2

1. Perform the PCM Power and Ground Check and the Powertrain Ground Check and return to this step.

Was a repair made in either check?

--

Go to Powertrain OBD System Check

Go to Step 3

3

1. Ensure battery is fully charged and tested.
2. Using DVM J 39200, measure voltage between DLC terminals 4 and 16.
3. Using DVM J 39200, measure voltage between DLC terminals 5 and 16.

Is the voltage read on both terminals the same or higher than the value shown?

10.0 Volts

Go to Step 7

Go to Step 4

4 | Measure voltage to ground on DLC terminal 16. Is the voltage read the same or higher than the value shown? | 10.0 Volts | Go to Step 5 | Go to Step 6
5 | Repair the open in the ground circuit that had low or no voltage. Refer to Test Descriptions . Is the repair complete? | -- | Go to Step 7 | --

6

1. Repair open or short to ground in CKT 1740 between DLC terminal 16 and B+.
2. Replace fuse if blown.

Is the repair complete?

--

Go to Step 7

--

7 | Turn the ignition ON. Does the scan tool display data? | -- | Go to Powertrain OBD System Check | Go to Step 8
8 | Connect the scan tool to another vehicle. Does the scan tool now display data? | -- | Go to Step 9 | Go to Step 13

9

1. Return to original vehicle.
2. Attempt to enter On-Board Diagnostics.

Does the vehicle enter On-Board Diagnostics?

--

Go to Step 10

Go to Section 8 for diagnosis

10 | Using On-Board Diagnostic display, check for data stream DTCs for all the modules. Are any data stream DTCs set? | -- | Go to DTC(s) that are set. | Go to Step 11
11 | Check for an open CKT 1807 between the DLC connector terminal 2 and the CKT 1807 DLC/ PZM/ IPC/ Mem seat splice. Was an open found and repaired? | -- | Go to Powertrain OBD System Check | Go to Step 12

12

1. Check terminal contact at the DLC connector terminal 2.
2. Repair terminal contact if needed.
3. Exit On-Board Diagnostics.
4. Reconnect the scan tool.

Does the scan tool now display data?

--

Go to Powertrain OBD System Check

Go to Step 14

13 | Replace the scan tool. Is the replacement complete? | -- | Go to Powertrain OBD System Check | --
14 | Replace the PCM. Is the replacement complete? | -- | Go to Powertrain OBD System Check | --