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Home >> Pontiac >> 2004 >> GTO Standard >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Data Link Communication System >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with UART Data Line >> Circuit Description
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Circuit Description

The UART protocol utilizes a single wire bi-directional data line used to exchange information between the modules.

The following modules are connected to the serial data circuit:

Scan Tool Does Not Communicate with UART Data Line

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) Schematics 
Connector End View Reference: Data Link Communications Connector End Views 
1 Did you perform the Diagnostic System Check for the non-communicating system. Go to Step 2  Refer to the appropriate diagnostic system check
2
  1. Connect the scan tool to the DLC.
  2. Turn ON the ignition, with the engine OFF.
  3. Attempt to communicate with each module on the serial data circuit:
    • Powertrain interface module (PIM)
    • Body control module (BCM)
    • Instrument panel cluster (IPC)
    • Electronic brake control module (EBCM)
    • Sensing and diagnostic module (SDM)
    • Radio
Does the scan tool communicate with all the modules on the serial data circuit?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3
  1. Disconnect the scan tool from the DLC.
  2. Disconnect all non-communicating modules on the serial data circuit.
  3. Test the serial data circuit between the DLC and all the modules on the serial data circuit, for the following conditions:
    • An open
    • A short to ground
    • A short to voltage
Refer to Data Link Connector (DLC) Schematics .Did you find and correct the condition?		 Go to Step 7  Go to Step 4 
4 Test the following circuits of the module that is not communicating for an open or high resistance:
  • The battery positive voltage input circuits
  • The battery positive voltage output circuits
  • The ignition voltage input circuits
  • The ignition voltage output circuits
  • The switched battery positive voltage supply circuits
  • The ground circuits

Refer to Data Link Connector (DLC) Schematics .
Did you find and correct the condition?		 Go to Step 7  Go to Step 5 
5 Inspect for poor connections and terminal tension at the following harness connector circuits, of the module that is not communicating :
  • The battery positive voltage input circuits
  • The battery positive voltage output circuits
  • The ignition voltage input circuits
  • The ignition voltage output circuits
  • The switched battery positive voltage supply circuits
  • The ground circuits
  • The serial data circuits

Refer to Data Link Connector (DLC) Schematics .
Did you find and correct the condition?		 Go to Step 7  Go to Step 6 
6
IMPORTANT: Perform the programming or set up procedure for the module if required, after it is replaced.
Replace the module that is not communicating on the serial data circuit. Refer to the applicable replacement procedure.Did you complete the replacement?		 Go to Step 7  -
7
  1. Connect all modules and connectors.
  2. Connect the scan tool to the DLC.
  3. Turn ON the ignition, with the engine OFF.
  4. Perform the Diagnostic System Check for the system exhibiting symptoms.
Did you complete the operation?		 System OK Go to Step 2 
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