Data Link Connector Diagnosis and MIL On Steady
Refer to
Ignition, Ground, and MIL Voltage
.
Circuit Description
The DLC supplies battery power and a ground to the scan tool. The Class 2 serial data circuit to the DLC allows the PCM to communicate with the scan tool. A UART serial data line is used to communicate with other modules such as the Electronic Brake Control Module (EBCM) and the Supplemental Inflatable Restraint (SIR) system.
Diagnostic Aids
Some scan tools may require an external power supply. Make sure the scan tool is using the correct power feed.
On the scan tool, select the correct application (model year, carline, VIN code). If you cannot establish communication still, try the scan tool on another vehicle in order to ensure that the scan tool, the Vehicle Interface Module (VIM), or the cables are not the cause of the conditions.
A poor connection, rubbed through wire insulation, or a wire broken inside the insulation may cause an intermittent.
Thoroughly check any circuitry, that you suspect is causing an intermittent complaint, for the following conditions:
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Physical damage to the wiring harness |
| • | Corrosion |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
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If the scan tool requires an external power supply, check the external supply for the proper voltage and ground as well as the voltage and ground supplies in the DLC.
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Unlike the UART serial data circuit, the only time the Class 2 serial data circuit has any voltage ON it is when the scan tool requests the PCM for information and the PCM sends the information out.
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If no voltage condition was due to an open fuse, repair any shorts that may have caused the fuse to open before replacement.
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Refer to the Diagnostic Aids if the scan tool will not display the scan data. If you were sent here from the OBD System Check table, return to that table and complete the diagnostics there.
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Reprogram the replacement PCM. Refer to the latest Techline information for the programming procedures.
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The scan tool, VIM or the associated cables could be faulty. refer to the scan tools manual for repair information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Turn ON the ignition leaving the engine OFF. Is the MIL ON? | -- | |||
3 |
Important: Go to Step 6 if the scan tool uses an external power supply, refer to the test description. Does the scan tool power up? | -- | ||
4 |
Does the MIL turn ON and OFF when commanded. | -- | ||
5 |
Is the MIL OFF? | -- | ||
Does the test lamp remain OFF? | -- | |||
7 | With the test lamp connected to ground, probe terminal 16 at the DLC connector. Does the test lamp illuminate? | -- | ||
8 | With a test lamp connected to B+, probe terminal 2 at the DLC connector. Does the test lamp remain OFF? | -- | ||
9 |
Was a repair necessary? | -- | ||
10 | With a test lamp connected to B+, probe the specified DLC ground circuit terminals. Does the test lamp illuminate for both circuits? | 4,5 | ||
Repair the open or the short to ground in the DLC battery feed circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | ||
Was a repair necessary? | -- | |||
13 |
Was a repair necessary? | -- | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
15 | Repair the open in the DLC ground circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
16 | Reinstall the scan tool. Can the scan tool communicate with the PCM? | -- | ||
17 | Install the scan tool on another vehicle in order to check for proper operation. Does the scan tool work properly on a different vehicle? | -- | ||
Scan tool is faulty. Refer to the scan tool manual for repair information. Is the action complete? | -- | -- | ||
19 |
Was a repair necessary? | -- | -- | |
20 |
Does the engine start and continue to run? | -- | ||
21 |
Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK Go to Diagnostic Aids |
