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 3640 to terminal 16. The ground to the scan tool is supplied through CKT 351 to terminal 5. The serial data (communication) is supplied to the scan tool through CKT 1807 to terminal 2.
Diagnostic Aids
Perform the Powertrain On Board Diagnostic (OBD) System Check before performing this chart to help prevent miss-diagnosis.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table:
-
If the ground circuit on the DLC pin 4 opens after the scan tool is up and running, the screen will go blank but the scan tool may remain on. If there is no ground at pin 4 initially, the scan tool will not power up.
-
Some of the older scan tools are powered through a separate power cord from the cigar lighter. If this type of scan tool is being used, and the tool will not power up, check for a poor connection, or a malfunctioning lighter socket.
-
If there is no communication between the PCM and the scan tool, no data will be displayed. The serial data is disrupted when the system voltage is below 9.0 Volts or above 16.0 Volts. A scan tool will not display data if the system voltage is outside of this range. If data is displayed with the ignition on and the engine off, but data is lost when the engine is running, high system voltage (overcharging) may be at fault. If this is the case, the scan tool should display DTC P0563 System Voltage with the ignition on and the engine off.
-
Try the scan tool on another vehicle if one is available. An alternate approach is to try a different scan tool on the same vehicle, if one is available. Before trying a different scan tool, check for poor connections between the DLC and the scan tool cable.
-
Before trying a different scan tool, check for poor connections between the DLC and the scan tool cable.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the scan tool powered up? | -- | |||
3 | Does the engine start and run? | -- | ||
4 |
Is the voltage in the range specified on all circuits? | 10.5 - 15 volts | ||
5 | Measure resistance on the PCM ground circuits in the PCM harness connector C1 with DMM J 39200 connected to battery ground. Does the DMM indicate the value shown or lower? | 5 Ohms | ||
6 | Repair the affected power feed circuit. Is the action complete? | -- | -- | |
7 | Repair the open/high resistance in the affected ground circuit. Is the action complete? | -- | -- | |
Is the voltage in the range specified? | 10.5 - 15 volts | |||
9 | Measure resistance on DLC terminal 4 and terminal 5 with DMM J 39200 connected to battery ground. Does the DMM indicate the value shown or lower on both circuits? | 5 Ohms | ||
10 | Repair the B+ circuit to DLC terminal 16. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check
| -- |
11 |
Is the voltage within the specified range on both circuits? | 10.5 - 15 volts | ||
Check the Serial Data circuit to DLC Pin 2 for being open, shorted to power or ground. Refer to Data Link Communications System Check in Wiring Systems for serial data circuit diagnosis. Was a problem found and corrected? | -- | |||
13 | Repair the open/high resistance ground circuit to DLC connector. Is the action complete? | -- | -- | |
Verify the scan tool operation on another vehicle. Refer to Test Description . Does the scan tool display data? | -- | |||
15 | Check for poor connections/terminal tension at the PCM harness connector. Was a problem found and corrected? | -- | ||
16 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
The scan tool may be malfunctioning. Use a different scan tool if one is available. Refer to Test Description . Is the action complete? | -- | -- |
