DTC 21

Connectors:

DTC 21: Short Circuit Communication Line

CIRCUIT OPERATION
ETACS-ECU, column switch (incorporated in ECU), front-ECU and sunroof motor assembly (incorporated in ECU) communicate with each other through the SWS communication line.

DTC SET CONDITION
This DTC is displayed when the SWS communication line remains at low level for 0.3 seconds. No other DTC is displayed if DTC 21 is displayed.

TROUBLESHOOTING HINTS
- The ETACS-ECU may be defective
- The column switch may be defective
- The front-ECU may be defective
- The sunroof motor assembly may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB991502: Scan Tool (MUT-II)













STEP 1. Check the ETACS-ECU connector C-318, column switch connector C-203, front-ECU connector A-11X and sunroof motor assembly connector D-08 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are ETACS-ECU connector C-318, column switch connector C-203, front-ECU connector A-11X and sunroof motor assembly connector D-08 in good condition?

YES : Go to Step 2.

NO : Repair or replace the damaged components). Refer to Harness Connector Inspection. Confirm the DTC 21 is not displayed. Diagrams



















STEP 2. Check the wiring harness from ETACS-ECU connector C-318 (terminal 59) to column switch connector C-203 (terminal 3), front-ECU
connector A-11X (terminal 22) and sunroof motor assembly connector D-08 (terminal 10).

NOTE: Also check intermediate connectors C-28 and C-209 and joint connector C-141 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connectors C-28 and C-209 and joint connector C-141 are damaged, repair or replace the damaged components) as described in Harness Connector Inspection. Diagrams

Q: Are the wiring harness from ETACS-ECU connector C-318 (terminal 59) to column switch connector C-203 (terminal 3), front-ECU connector A-11X (terminal 22) and sunroof motor assembly connector D-08 (terminal 10) in good condition?

YES : Go to Step 3.

NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Confirm the DTC 21 is not displayed.




STEP 3. Check the column switch.
Disconnect column switch connector C-203.

Q: Does DTC 21 set?

YES : Go to Step 4.

NO (DTC 12 sets) : Replace the column switch. Confirm the DTCs 12 and 21 are not displayed.




STEP 4. Check the front-ECU.
Disconnect front-ECU connector A-11X.

Q: Does DTC 21 set?

YES : Go to Step 5.

NO (DTC 13 sets): Replace the front-ECU. Confirm the DTCs 13 and 21 are not displayed.




STEP 5. Check the sunroof motor assembly.
Disconnect sunroof motor assembly connector D-08.

Q: Does DTC 21 set?

YES : Replace the ETACS-ECU. Confirm the DTC 21 is not displayed.

NO : Replace the sunroof motor assembly. Confirm the DTC 21 is not displayed.