Vibe FWD L4-1.8L VIN 8 (2004)
Scan Tool Does Not Communicate With Vehicle Control Module/Powertrain Control Module
Scan Tool Does Not Communicate with Vehicle Control Module/Powertrain Control Module
Circuit Description
The provision for communicating with the powertrain control module (PCM) is the data link connector (DLC). The DLC is located under the
instrument panel (IP). The DLC is used to link a scan tool to the PCM serial data stream. Some common uses of the scan tool are listed below:
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Identifying the stored diagnostic trouble codes (DTCs).
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Reading the serial data stream.
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Clearing the DTCs.
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Storing the Freeze Frame data.
Diagnostic Aids
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 (model 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.
An intermittent malfunction may be caused by a fault in the Heated Oxygen Sensor (HO2S) circuit. Inspect the wiring harness and components for an
intermittent condition. Refer to Intermittent Conditions.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. 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.
5. The modules supply a low current (about 1.85 mA) voltage on the serial data circuit. The normal circuit low current will NOT illuminate a test
lamp. If the circuit is shorted to battery positive the higher current will illuminate the test lamp.
7. This step checks whether the PCM is receiving ignition positive voltage from the EFI relay when the ignition is ON. The PCM cannot provide
serial data without ignition positive voltage from the EFI relay.
8. If the engine starts and runs, the EFI relay is OK.
9. The PCM cannot provide serial data without the correct power and grounds.
13. The scan tool may be damaged by high current flow on the serial data circuit at DLC terminal 7. Inspect the scan tool for proper operation on a
known good vehicle that uses terminal 7 of the DLC for serial data communication.
15. A shorted sensor reference voltage circuit can cause a loss of scan tool communication with the PCM.