DTC 21

Short circuit communication line

SWS Communication Circuit:

Connector:

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
- Malfunction of the ETACS-ECU
- Malfunction of the column switch
- Malfunction of the front-ECU
- Malfunction of the sunroof motor assembly
- Damaged harness wires or connectors

DIAGNOSIS

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













STEP 1. Check the ETACS-ECU connector C-313, column switch connector C-203, front-ECU connector A-09X and sunroof motor assembly connector D-08 for damage.

Q: Are ETACS-ECU connector C-313, column switch connector C-203, front-ECU connector A-09X and sunroof motor assembly connector D-08 in good condition?

YES: Go to Step 2.
NO: Repair or replace them. Refer to Harness Connector Inspection. Confirm the DTC 2115 not displayed.













STEP 2. Check the harness wires from ETACS-ECU connector C-313 to column switch connector C-203, front ECU connector A-09X and sunroof motor assembly connector D-08.






NOTE: After inspecting intermediate connectors C-28 and C-209 and joint connector C-141, check the wires. If intermediate connectors C-28 and C-209 and joint connector C-141 are damaged, repair or replace them. Refer to Harness Connector Inspection.

Q: Are the harness wires from ETACS-ECU connector C-313 to column switch connector C-203, front-ECU connector A-09X and sunroof motor assembly connector D-08 in good condition?

YES: Go to Step 3.
NO: Replace them. 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-09X.

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.