GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 1999 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 Data Link Connector Diagnosis

Refer to.

Circuit Description

There should always be a Malfunction Indicator Lamp (MIL) when the ignition is ON and engine OFF. Battery ignition voltage is supplied to the lamp. The PCM will turn the lamp ON by grounding the ignition feed circuit.

Test Description

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

  1. This step verifies if the problem is in the scan tool or the vehicle.

    2.

  2. This step will check the ground circuits at the data link connector (DLC).

    3.

  3. The step will check for the battery and ignition feeds to the PCM.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing any DTCs, use the scan tool Capture Info to save freeze frame and failure records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain OBD System Check

2

Important: This table assumes that the scan tool you are using is functional.

  1. Turn ON the ignition leaving the engine OFF.
  2. Connect the scan tool to the DLC.

Does the scan tool power-up?

--

Go to Step 3

Go to Step 5

3
  1. Turn OFF the ignition for 15 seconds.
  2. Attempt to start the vehicle.

Does the engine start then stall?

--

Go to Wiring Repairs

Go to Step 4

4

Did the engine just crank over and not start?

--

Go to Step 9

Go to Step 13

5
  1. Disconnect the scan tool from the DLC.
  2. Turn ON the ignition leaving the engine OFF.
  3. Probe the DLC terminal 16 using an J 35616-200 unpowered test lamp connected to battery ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 16

6

Probe the DLC terminals 4 and 5 using an J 35616-200 unpowered test lamp connected to B+.

Does the test lamp illuminate on both circuits?

--

Go to Step 7

Go to Step 8

7
  1. Inspect the scan tool connections to the DLC.
  2. Also inspect the terminals for proper tension at the DLC. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain OBD System Check

--

8

Repair the open ground circuit to the DLC terminals 4 and 5. Refer to Wiring Repairs.

Is the action complete?

--

Go to Powertrain OBD System Check

--

9

  1. Turn the ignition OFF.
  2. Disconnect the PCM connector containing the Battery and Ignition feed circuits.
  3. Turn the ignition ON.
  4. Probe the ignition feed circuit C1-18 in the PCM harness connectors with an J 35616-200 unpowered test lamp connected to battery ground.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 14

10

Measure the resistance between the battery ground and the PCM ground circuits in the PCM harness connectors using a DMM.

Does the DMM display the specified value (or lower) on each circuit?

5 ohms

Go to Step 11

Go to Step 15

11

Inspect the PCM for proper connections. Refer to Wiring Repairs .

Was a repair performed?

--

Go to Powertrain OBD System Check

Go to Step 12

12

Important: The new PCM must be programmed. Refer to PCM Replacement/Programming.

Replace the PCM.

Is the action complete?

--

Go to Powertrain OBD System Check

--

13

Repair the Class 2 circuit for being open between the splice and the DLC. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain OBD System Check

--

14

Repair the circuit that did not illuminate the test lamp. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain OBD System Check

--

15

Repair the PCM ground circuit(s). Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain OBD System Check

--

16

Repair the B+ supply circuit. Refer to Wiring Repairs .

Is the action complete?

--

Go to Powertrain OBD System Check

--