GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Modules connected to the keyword data circuit monitor data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A partial malfunction in the keyword data circuit uses a different procedure from a total malfunction of the circuit. The following modules communicate on the keyword data circuit.

  2. • Communication interface module (OnStar®)
    • Brake pressure modulator valve (BPMV)
    • Inflatable restraint sensing and diagnostic module (SDM)
    • Front passenger presence system module (PPS)
    • Powertrain control module (PCM)
  3. An open in the serial data circuit between the DLC and splice S232 will prevent the scan tool from communicating with any module on the network. This condition will not set a DTC.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn ON the ignition, with the engine OFF.
  2. Perform the Vehicle DTC Information function on the scan tool under Computer/Integrating Systems menu.

Are any DTC's retrieved from any module?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 3

3

Did the scan tool communicate with any module on the keyword data circuit?

Go to Step 4

Go to Step 5

4

Diagnose the non-communicating module by referring to the appropriate section.

Did you complete the action?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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5

  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 6

6

Repair the keyword data circuit between the DLC and the splice S232 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the action?

System OK

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