GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Regal (China) (CNG) 🢒 Engine 🢒 Engine Controls - 3.0L (L46) 🢒 Data Link Connector Diagnosis

Circuit Description

The Class II serial data circuit to the DLC allows bi-directional communication between the PCM and the scan tool. If communication between the scan tool and the PCM cannot be established, the procedure in the DLC Diagnosis table should be used to diagnose the condition.

Diagnostic Aids

Check the following items:

    •  For the PCM to establish communication with the scan tool, system voltage must be between 9.0 and 16.0V. If system voltage is not within this range, refer to Charging System Check for diagnosis.
    •  Ensure that the correct application (model year, carline, VIN code) has been selected on the scan tool, if communication still cannot be established try the scan tool on another vehicle to ensure that the scan tool, Vehicle Interface Module, or cables are not the cause of the condition.
    •  An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for poor connections or a damaged harness. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs .

Test Description

The number below refers to the step number on the Diagnostic Table:

  1. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain OBD System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn the ignition on and leave the engine off.
  2. Connect a J 35616-200 test light between the DLC battery feed and ground circuits. (Terminals 4 and 5).

Is the J 35616-200 test light on?

--

Go to Step 4

Go to Step 3

3

Probe the DLC battery feed circuit with a J 35616-200 test light to chassis ground.

Is the J 35616-200 test light on?

--

Go to Step 9

Go to Step 10

4
  1. Turn the ignition on, and leave the engine off.
  2. Probe the Class II serial data circuit at the DLC with a J 39200 DMM to ground.

Does the voltage measure the specified value?

0.0V

Go to Step 5

Go to Step 7

5
  1. Turn the ignition off.
  2. Disconnect the PCM.
  3. Turn the ignition on, and leave the engine off.
  4. Probe the Class II serial data circuit at the DLC with a J 39200 DMM connected to battery positive voltage.

Does the voltage measure the specified value?

0.0V

Go to Step 6

Go to Step 8

6
  1. Check the Class II serial data circuit for an open between the DLC and the PCM
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

7
  1. Check the Class II serial data circuit for a short to voltage.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

8

Locate and repair short to ground in the Class II serial data circuit. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

9

Locate and repair open in the DLC ground circuit(s) (Terminal 4 or 5). Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

10

Locate and repair open or short to ground in the DLC battery feed circuit. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

11

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--