DTC 21
Short Circuit Communication LineSWS Circuit Communication Line:
Connectors:
CIRCUIT OPERATION
ETACS-ECU, column switch (incorporated in ECU) and front-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 not displayed if DTC 21 is displayed.
TROUBLESHOOTING HINTS
- Malfunction of the ETACS-ECU
- Malfunction of the column switch
- Malfunction of the front-ECU
- 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-82, column switch connector C-60 and front-ECU connector A-09X for damage.
If the ETACS-ECU connector C-82, column switch connector C-60 and front-ECU connector A-09X are damaged repair or replace them. Refer to Harness Connector Inspection.
Confirm the DTC 21 is not displayed.
If connectors are in good condition go to Step 2.
STEP 2. Check the harness wires from ETACS-ECU connector C-82 to column switch connector C-60 and front-ECU connector A-09X.
NOTE: After inspecting intermediate connector C-66, check the wires. If intermediate connector C-66 is damaged, repair or replace it. Refer to Harness Connector Inspection.
If the harness wires from ETACS-ECU connector C-82 to column switch connector C-60 and front-ECU connector A-09X are damaged, repair them.
Confirm the DTC 21 is not displayed.
If the harness wires are in good condition, go to Step 3.
STEP 3. Check the ECUs.
Disconnect column switch connector C-60 and front-ECU connector A-09X in that order one by one. Then check that DTC 21 does not reset under any conditions.
If DTC 21 does not set (DTC 12 sets) when column switch connector C-60 is disconnected, replace the column switch.
Confirm the DTCs 12 and 21 are not displayed.
If DTC 21 does not set (DTC 13 sets) when front-ECU connector A-09X is disconnected, replace the front-ECU.
Confirm the DTCs 13 and 21 are not displayed.
If DTC 21 resets when any of the above connectors is disconnected, replace the ETACS-ECU.
Confirm the DTC 21 is not displayed.