GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Grand Prix 🢒 Body and Accessories 🢒 Data Link Communications 🢒 Scan Tool Does Not Communicate with Class 2 Data Line

Step

Action

Value(s)

Yes

No

1

Use a DMM in order to measure the voltage between the Data Link Connector (CLC) terminal 16 and ground.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 2

Go to Step 11

2

Use a DMM in order to measure the voltage between B+ and the DLC terminal 5.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 2

Go to Step 12

3

Use a DMM in order to measure the voltage between B+ and DLC terminal 4.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 4

Go to Step 12

4

Inspect for a proper connection of the scan tool to the DLC.

Is the connection OK between the scan tool and the DLC?

--

Go to Step 5

Go to Step 13

5

Attempt to establish communication with the PCM on a different vehicle using the scan tool.

Can communication be established with the scan tool?

--

Go to Step 6

Go to Step 14

6
  1. Reconnect the scan tool to the DLC.
  2. Turn the ignition switch to the RUN position.
  3. Using a scan tool, re-attempt to establish communication with the Powertrain Control Module (PCM).

Can the scan tool communicate with the PCM?

--

Go to Step 15

Go to Step 7

7
  1. Turn the ignition switch OFF.
  2. Disconnect the PCM connector C1.
  3. Use a DMM in order to measure the resistance between the DLC terminal 2 and the DLC terminal 5.

Is the resistance the same as the specified value?

OL (Infinite)

Go to Step 8

Go to Step 16

8
  1. Turn the ignition switch to the RUN position.
  2. Use a DMM in order to measure the voltage between the DLC terminal 2 and the DLC terminal 5.

Is the voltage less than the specified value?

1 V

Go to Step 9

Go to Step 17

9

Use a DMM in order to measure the resistance between the DLC terminal 2 and the PCM connector C1 terminal 59.

Is the resistance within the specified value?

0-2 ohms

Go to Step 10

Go to Step 18

10

Inspect for power, ground and proper connections to the PCM. Refer to Engine Controls for additional information.

Is the action complete?

--

Go to Step 19

--

11

Repair the poor connection or an open in circuit 440.

Is the repair complete?

--

Go to Step 19

--

12

Repair the poor connection or an open in circuit 1550.

Is the repair complete?

--

Go to Step 19

--

13

Repair the poor connection between the DLC terminal 2 and the scan tool.

Is the repair complete?

--

Go to Step 19

--

14

The scan tool may be malfunctioning. Refer to the scan tool instruction manual for additional information.

Is the action complete?

--

Go to Step 19

--

15

The malfunction is intermittent and not present at this time. Inspect the PCM connectors for the following conditions:

    • A poor connection or open
    • A short to B+
    • A short to ground in circuit 1807.

Repair as needed.

Is the action complete?

--

Go to Step 19

--

16

Repair the short to ground in circuit 1807.

Is the repair complete?

--

Go to Step 19

--

17
  1. Turn the ignition OFF.
  2. Repair the short to B+ in circuit 1807.

Is the repair complete?

--

Go to Step 19

--

18

Repair the poor connection or an open in circuit 1807.

Is the repair complete?

--

Go to Step 19

--

19
  1. Ensure that the ignition switch is OFF.
  2. Reconnect the connectors. Reinstall the components.

Is the action complete?

--

Go to A Diagnostic System Check - Data Link Communications

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