SWS Diagnostic Troubleshooting Strategy

SWS DIAGNOSTIC TROUBLESHOOTING STRATEGY

1. Gather information about the problem from the customer.
2. Verify that the condition described by the customer exists.
NOTE:
If an error occurs in the SWS communication line, the ECU isolated from the communication line performs a fail-safe or backup operation, so the problem may not match the one shown in the Trouble Symptom Chart. However, the cause of the failure can be tracked down by performing the following troubleshooting with the SWS monitor.

3. Version number and destination check
Check whether the SWS version number (1) and destination (North America) meet the vehicle specifications. If they are different, replace the ETACS-ECU with a correct one.
4. Use scan tool MB991958 (M.U.T.-III Sub Assembly) to select "ECU COMM Check" on the SWS monitor display.
Check whether the communication status of the input- or output-signal-side ECU associated with the defective function is normal.

- If "OK" is displayed for all related ECUs, they communicate with each other normally and the input or output signal circuit system may be defective. Therefore, check SWS monitor service data.
- If "NG" is displayed for any of the related ECUs, something may be wrong with the ECU for which "NG" appears, its power supply or grounding system, or a wiring harness or connector between the SWS monitor and the ECU. Check the wiring harness and connectors associated with the ECU and examine the ECU itself.
5. Service data on the SWS monitor
Select the defective function from the function-specific diagnostic menu, and check the service data that appears for each function item.
When the SWS communication line is monitored, you can determine whether the problem lies in the input or output signal circuit system by checking whether communication data is correct:

- If the switch condition does not meet the service data display, the input signal is defective.
- If the switch condition meets the service data display, the output signal system is defective.

NOTE:
In addition to the function-specific diagnostic menu, a service data menu is available for SWS monitor service data to check all items for each ECU.

6. Check the input signal circuit system
Check the relevant switch, sensor, input signal-side ECU and their wiring harness and connector.
7. Check the output signal circuit system
Check an output signal-side ECU, electrical load components and their wiring harness and connector.