GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Lumina 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Scan Tool Does Not Communicate with UART Data Line

Step

Action

Value(s)

Yes

No

1

Does the scan tool power up?

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Go to Step 2

Go to Scan Tool Does Not Power Up

2
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with each module on the UART data line circuit.

Does any module on the UART serial data circuit communicate with the scan tool?

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Go to Step 6

Go to Step 3

3

Test the battery positive voltage circuit(s) and the ignition circuit(s) of the Powertrain Control Module (PCM) for an open. Refer to Control Module References for PCM schematics. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Control Module References for the applicable Diagnostic System Check

Go to Step 4

4
  1. Turn off the ignition switch.
  2. Test the ground circuit(s) of the PCM for an open. Refer to Control Module References for PCM schematics. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 5

5

Test the UART serial data circuit between the DLC and the PCM, for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 8

6

Test the battery positive voltage circuit(s) and the ignition voltage circuit(s) of the module that will not communicate with the scan tool for an open or a short to ground. Refer to Control Module References for the applicable schematics. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 7

7
  1. Turn off the ignition switch.
  2. Test the ground circuit(s) of the module that will not communicate for an open. Refer to Control Module References for the applicable schematics. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the scan tool, if connected.
  3. Disconnect all the modules on the UART data line circuit.
  4. Test the UART data line circuit for a short to ground or a short to voltage, (Turn ON the ignition, with the engine OFF, when testing for a short to voltage) Refer to Circuit Testing and Wiring Repairs in Wiring Systems, between the following:
    5. • DLC
    • PCM
    • EBCM
    • SDM

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 9

9

Test the UART serial data circuit between the DLC, PCM, EBCM and the SDM for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 10

10
  1. Turn OFF the ignition
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections at the DLC terminals 5 and 9. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

.

Did you find and correct the condition?

--

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 11

11

Replace the module that would not communicate on the UART serial data circuit. Refer to Control Module References for the replacement procedure.

Is the repair complete?

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System OK

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