Scan Tool Does Not Communicate with Class 2 Data Line. Chevrolet Chevy C Silverado

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy C Silverado - 2WD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Scan Tool Does Not Communicate with Class 2 Data Line

Step

Action

Value(s)

Yes

For a full view of the schematic refer to Data Link Connector Schematics .

Can the scan tool be powered up?

Go to Step 9

Go to Step 2

Disconnect the scan tool from the data link connector, (DLC).
Inspect for a proper connection of the scan tool to the data link at terminals 4 and 16.

Is the connection good?

Go to Step 3

Go to Step 5

Measure the voltage from terminal 16 of the DLC to ground.

Is voltage within the specified range?

12.0 -14.8 V

Go to Step 4

Go to Step 7

Measure the resistance from terminal 4 of the DLC to ground.

Is resistance within the specified range?

0-5ohms

Go to Step 6

Go to Step 8

Repair the connection as needed.

Is the repair complete?

System OK

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

Has a properly operating scan tool been obtained?

Go to Step 1

Repair the open in CKT 640 (ORN).

Is the repair complete?

System OK

Repair the open in CKT 1850 (BLK).

Is the repair complete?

System OK

Turn the ignition switch to RUN.
Using the scan tool, attempt to establish communication with each module on the class 2 data link:

•

ATC

•

IPC

•

VCM/PCM

•

EBCM

•

BCM

If using a Tech 2, the Class 2 Message Monitor feature can be used in order to obtain this information

Are there any modules on the class 2 data link which are communicating?

Go to Step 10

Go to Step 13

Are DTCs U1000 and/or U1xxx (Lost Communications With XXX) set in the modules which will communicate?

Go to Step 11

Go to Step 12

Diagnose the malfunction using the class 2 communication malfunction (U1000) or the class 2 lost communication with XXX (U1xxx) procedures as appropriate.

Is the procedure complete?

System OK

Diagnose the malfunction using the class 2 lost communication with XXX (U1xxx) procedures for the module which is not communicating.

Is the procedure complete?

System OK

Turn the ignition switch to OFF.
Inspect for proper connection of the scan tool to the data link at terminal 5.

Is the connection good?

Go to Step 14

Go to Step 5

Measure the resistance from terminal 5 of the DLC to ground.

Is resistance within the specified range?

0-5ohms

Go to Step 15

Go to Step 30

Inspect for a proper connection of the scan tool to the data link connector at terminal 2.

Is the connection good?

Go to Step 16

Go to Step 5

Disconnect splice pack 205 (SP205). Refer to Data Link Connector Schematics .
Inspect for a proper connection of the class 2 serial data circuit to terminal A of the splice pack.

Is the connection good?

Go to Step 17

Go to Step 5

Measure the resistance from terminal 2 of the DLC to terminal A of the splice pack.

Is the resistance within the specified range?

0-5ohms

Go to Step 18

Go to Step 29

Measure the resistance on the DLC from terminal 2 to terminal 4.

Is the resistance as specified?

OL (Infinite)

Go to Step 19

Go to Step 28

Turn the ignition switch to RUN.
Measure the voltage on the DLC from terminal 2 to terminal 4.

Is the voltage within the specified range?

0-1 volt

Go to Step 20

Go to Step 27

Turn the ignition switch to OFF.
Using the correct terminal adapter from J 35616-A, connect a jumper wire to terminal A of the splice pack 205 (SP205) which is connected to a module.
Connect the other end of the jumper wire (with the correct terminal adapter) to a terminal in the SP205 which is connected to a module.
Turn the ignition switch to RUN.
Using the scan tool, attempt to establish communication with the module which is jumpered to the DLC.

Can communication be established?

Go to Step 21

Go to Step 22

Repeat step 20 for each module on the Class 2 serial data link.

Can communication be established for each module on the Class 2 serial data link?

Go to Step 31

Go to Step 22

Turn the ignition switch to OFF.
Disconnect the module which does not communicate.
Measure the resistance from the SP205 terminal of the Class 2 serial data circuit for the disconnected module to ground.

Is the resistance as specified?

OL (Infinite)

Go to Step 23

Go to Step 28

Turn the ignition switch to RUN.
Measure the voltage from the Class 2 serial data circuit of the disconnected module to ground.

Is the voltage within the specified range?

0-1 volt

Go to Step 24

Go to Step 27

Turn the ignition switch to OFF.
Inspect the connector of the disconnected module in the area of the class 2 serial data circuit for backed out terminals which would cause a short to ground or voltage.

Are all terminals properly locked into the connector body?

Go to Step 25

Go to Step 5

Replace the module which does not communicate. Refer to the appropriate On-Vehicle Service procedures from the following list for the module being replaced in order to ensure a complete repair.

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Reconnect the SP205. Refer to Data Link Connector Schematics .
Reconnect all the modules on the class 2 serial data link.
Turn the ignition switch to RUN.
Using the scan tool, attempt to establish communication with the module which was replaced.

Can communication be established?

Go to Step 31

Go to Step 26

Replace the class 2 serial data circuit wire between the splice pack 201 (SP201) and the module which does not communicate. Refer to Data Link Connector Schematics .

Is the repair complete?

Go to Step 31