The provisions for communicating with the engine control module (ECM), electronic brake control module (EBCM), SIR module, Immobilizer Module, and the Theft Deterrent module are located in the data link connector (DLC). The DLC is located under the instrument panel (I/P). The 16 pin DLC provides the serial data signal at terminals 7 (ECM, TCM, ABS and ISU serial data), terminals 3 (2.5 L speed sensitive power steering), terminals 14 (2.0 L speed sensitive power steering), and terminals 13 (SIR serial data). The DLC is used to link a scan tool to the ECM, EBCM, SIR, intelligent switching unit (ISU), and speed sensitive steering module (SSPS) serial data stream. Some common uses of the scan tool are listed below:
• | Identifying the stored diagnostic trouble codes (DTC) |
• | Reading the serial data stream |
• | Clearing the DTCs |
• | Storing the Freeze Frame data |
Some scan tools may require an external power supply . Ensure the scan tool is correctly connected to the power feed.
Ensure that the correct application (module year, carline, VIN code) has been selected on the scan tool. If communications are still not established, try the scan tool on another vehicle in order to ensure that the scan tool or the connecting cables are not the cause of the malfunction. Always try the scan tool on a vehicle that uses the same DLC terminal for serial data communication.
Any circuitry that is suspect to an intermittent complaint should be thoroughly inspected for the following:
The numbers below refer to the step numbers on the diagnostic table.
This step checks whether the scan tool can communicate with other control modules on the vehicle. If the scan tool can communicate with one of the other modules then the DLC connector, the shared Circuits, and the scan tool are OK.
This step checks whether the ECM is receiving ignition positive voltage from the fuse F16 when the ignition is ON. The ECM cannot provide serial data without ignition positive voltage.
This step checks for a high resistance or open/short in the ECM serial data circuit.
This step checks the ECM DLC Diagnostic circuit high resistance or open/short. This could cause the ECM not to communicate.
This step checks to see if the EBCM is not communicating with the scan tool.
This step checks to see if the SIR system is not communicating with the scan tool.
This step checks to see if the Theft Deterrent-Immobilizer system is not communicating with the scan tool.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Data Communication Schematics | |||
1 | Have you performed the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Does the scan tool power up? | Go to Step 3 | |
Does the scan tool communicate with the engine control module (ECM)? | Go to Step 9 | Go to Step 4 | |
With the ignition OFF:
Does the test lamp illuminate for all circuits? | Go to Step 5 | Go to Step 24 | |
5 | With the ECM still disconnected, test the ECM ground circuits with a test lamp connected to B+. Does the test lamp illuminate for all ground circuits? | Go to Step 6 | Go to Step 24 |
6 |
Does the scan tool display serial data? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 7 |
Test the serial data circuit for an open, high resistance, or a short circuit. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 29 | Go to Step 8 | |
Test the data link connector (DLC) diagnostic circuit for an open, high resistance or a short circuit. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 29 | Go to Step 25 | |
Does the scan tool communicate with the electronic brake control module (EBCM)? | Go to Step 14 | Go to Step 10 | |
10 | Test the EBCM battery positive (B+) and/or ignition voltage circuits with a test lamp to ground. Does the test lamp illuminate for all circuits? | Go to Step 11 | Go to Step 24 |
11 | Test the EBCM ground circuits with a test lamp connected to B+. Does the test lamp illuminate for all circuits? | Go to Step 12 | Go to Step 24 |
12 | Test the EBCM serial data circuit for an open, high resistance, or short circuit. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 29 | Go to Step 13 |
13 | Check the EBCM connectors. Refer to Wiring Repairs or Connector Repairs . Did you find and correct the condition? | Go to Step 29 | Go to Step 26 |
Does the scan tool communicate with the SIR module? | Go to Step 19 | Go to Step 15 | |
15 | Test the SIR module battery positive (B+) and/or ignition voltage circuits with a test lamp to ground. Does the test lamp illuminate for all circuits? | Go to Step 19 | Go to Step 24 |
16 | Test the SIR module ground circuits with a test lamp connected to B+. Does the test lamp illuminate for all circuits? | Go to Step 17 | Go to Step 24 |
17 | Test the SIR serial data circuit for an open, high resistance, or short circuit. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 29 | Go to Step 18 |
18 | Check the SIR Module connectors. Refer to Wiring Repairs or Connector Repairs . Did you find and correct the condition? | Go to Step 29 | Go to Step 27 |
Does the scan tool communicate with the intelligent switching unit (ISU)? | Go to Step 29 | Go to Step 20 | |
20 | Test the ISU battery positive (B+) and/or ignition voltage circuits with a test lamp to ground. Does the test lamp illuminate for all circuits? | Go to Step 21 | Go to Step 24 |
21 | Test the ISU ground circuits with a test lamp connected to B+. Does the test lamp illuminate for all circuits? | Go to Step 22 | Go to Step 24 |
22 | Test the ISU serial data circuit for an open, high resistance, or short circuit. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 29 | Go to Step 23 |
23 | Check the ISU connectors. Refer to Wiring Repairs or Connector Repairs . Did you find and correct the condition? | Go to Step 29 | Go to Step 28 |
24 | Repair the circuit as necessary. Is the action complete? | Go to Step 29 | -- |
25 | Replace the ECM. Refer to Control Module References for ECM replacement, setup and programming. Is the action complete? | Go to Step 29 | -- |
26 | Replace the EBCM. Refer to Brake Pressure Modulator Valve Assembly Replacement . Is the action complete? | Go to Step 29 | -- |
27 | Replace the SIR module. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Is the action complete? | Go to Step 29 | -- |
28 | Replace the ISU. Is the action complete? | Go to Step 29 | -- |
29 | Operate the system in order to verify the repair. Is the action complete? | System OK | Go to Step 3 |