DTC 21: Short Circuit Communication Line: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB991502: Scan Tool (MUT-II)

1. 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 component(s). Refer to , HARNESS CONNECTOR INSPECTION . Confirm the DTC 21 is not displayed.

   Fig 1: Identifying ETACS-ECU Connector C-318

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 2: Identifying Column Switch Connector C-203

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 3: Identifying Front-ECU Connector A-11X

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 4: Identifying Sunroof Motor Assembly Connector D-08

   Courtesy of DAIMLERCHRYSLER CORPORATION
2. 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). 
   Fig 5: Identifying ETACS-ECU Connector C-318

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 6: Identifying Column Switch Connector C-203

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 7: Identifying Front-ECU Connector A-11X

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 8: Identifying Sunroof Motor Assembly Connector D-08

   Courtesy of DAIMLERCHRYSLER CORPORATION
   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 component(s) as described in , HARNESS CONNECTOR INSPECTION .

   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.

   Fig 9: Identifying Intermediate Connectors C-28 And Joint Connector C-141

   Courtesy of DAIMLERCHRYSLER CORPORATION
   Fig 10: Identifying Intermediate Connectors C-209

   Courtesy of DAIMLERCHRYSLER CORPORATION
3. 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.

   Fig 11: Identifying Column Switch Connector C-203

   Courtesy of DAIMLERCHRYSLER CORPORATION
4. 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.

   Fig 12: Identifying Front-ECU Connector A-11X

   Courtesy of DAIMLERCHRYSLER CORPORATION
5. 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.

   Fig 13: Identifying Sunroof Motor Assembly Connector D-08

   Courtesy of DAIMLERCHRYSLER CORPORATION