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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Catera 🢒 Body and Accessories 🢒 Data Link Communications 🢒 Scan Tool Does Not Communicate with Keyword 82 Data Line

Scan Tool Does Not Communicate with Keyword 82 Data Line and Keyword 2000

Circuit Operation

Modules connected to the Keyword serial data circuit utilize a request and response type arrangement. Similar to the UART system. Operating information and commands are not exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes only.

The exception, however, are the engine control module (ECM), transmission control module (TCM), and EBTCM. These modules, in addition to the Keyword serial data circuits, exchange information via the controlled area network (CAN) data circuits. Diagnostic trouble codes (DTCs) are set by these modules when a condition exists with the CAN circuits or an important message is not received. Refer to the individual DTC tables to diagnose CAN malfunctions.

Diagnostic Aids
    • Use a J35616-A when probing or checking electrical connector terminals. The J35616-A prevents terminal damage, plus checks for proper terminal contact tension.
    • If the malfunction is intermittent refer to Inducing Intermittent Fault Conditions in Wiring Systems.

Test Description

  1. The data link connector terminal specific to the module that is not communicating and terminals 4 and 5, provide the connection to the Keyword serial data circuit and the signal ground circuit respectively.

    2.

  2. Proper power and ground to the module, that is not communicating, is essential.

  3. The Keyword serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wiring for a short, make sure there is not a module connected to the wire being tested.

    4.

  4. Since the short is not in the wiring harness the malfunction is due to one of the modules.

Step

Action

Yes

No

1

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2
  1. Turn on the ignition leaving the engine off.
  2. Attempt to communicate with each module connected to the module not communicating.
  3. Refer to the following list for module pairing:
    4. • Engine Control Module (ECM), Transmission Control Module (TCM), Memory Seat Module (MSM), and Instrument Cluster
    • Theft Deterrent Module (Immobilizer) and Sun Roof Actuator
    • SIR Module, Power Steering Control Module, Heater and A/C Control, and EBTCM

Does the scan tool communicate with the other module(s) on the serial data circuit?

Go to Step 3

Go to Step 4

3

Test the serial data circuit to the module that is not communicating for an open circuit. Refer to Testing for Continuity in Wiring Systems.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 5

4

  1. Turn off the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections/terminal tension at the DLC terminal specific to the module that is not communicating and terminals 4 and 5. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 6

5

Test the following to the module that is not communicating. Refer to Testing for Continuity and Testing for Short to Ground in Wiring Systems:

    • Battery positive voltage circuit(s) for an open or short to ground
    • Ignition positive voltage circuit(s) for an open or short to ground
    • Ground circuit for an open
    • In addition, for the ECM inspect and test the operation of the engine controls power relay (K43). Refer to Engine Controls Power Relay Circuit Diagnosis in Engine Controls.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 7

6

Test the DLC ground circuit terminals 4 and 5 for an open. Refer to Testing for Continuity in Wiring Systems.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 8

7

Inspect for poor connections/terminal tension at the serial data circuit of the module that is not communicating.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 9

8

    • Disconnect each module on the serial data circuit connected to the module that is not communicating.
    • Test the serial data circuit for a short to ground or short to voltage between the DLC terminal of the module that is not communicating and each module on the serial data circuit. (Turn on the ignition, leaving the engine off, when testing for a short to voltage.) Refer to Testing for Short to Ground and Testing for a Short to Voltage in Wiring Systems.

Did you find and correct the condition?

Go to the Applicable Diagnostic System Check

Go to Step 10

9

Replace the module that is not communicating.

Did you complete the replacement?

Go to the Applicable Diagnostic System Check

--

10

  1. Reconnect the module that was not communicating.
  2. Reconnect all disconnected in-line harness connectors.
  3. Install a scan tool.
  4. Turn on the ignition, with the engine off.
  5. Attempt to communicate with the module.

Does the scan tool communicate with the module?

Go to Step 11

Go to Step 14

11

Continue connecting the disconnected modules and attempting to communicate after each connection until communication cannot be established or all the modules are reconnected.

Did you find the condition?

Go to Step 12

Go to Diagnostic Aids

12

Replace the most recently reconnected module. Refer to the appropriate repair instructions for module replacement.

Did you complete the replacement?

Go to Step 13

 

13
  1. Reconnect all of the disconnected modules.
  2. Reconnect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn on the ignition leaving the engine off.
  5. Attempt to communicate with all the modules on the serial data circuit.

Does the scan tool communicate with the modules?

System OK

--

14

Inspect for poor connections/terminal tension at the serial data circuit of the most recently reconnected module. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9