DTC 21: Short In Communication Line: Testing

Check for poor connections at Column ECU, Electronic Timer Alarm Control System Electronic Control Unit (ETACS ECU), Front ECU and Sun Roof ECU connector terminals. See COMPONENT LOCATIONS . If poor connections are found, repair as necessary. Recheck for DTCs. If connections are okay, go to next step.
Check for faulty circuits between control units and joint connector. See COMMUNICATION LINE IDENTIFICATION table. If faulty circuits are found, repair as necessary. Recheck for DTCs. If circuits are okay, go to next step.
Using scan tool, clear DTCs. Disconnect Column ECU connector. Recheck for DTCs. If DTC 21 sets, go to next step. If DTC 21 does not set, replace Column ECU. See COLUMN ECU under REMOVAL & INSTALLATION.
Disconnect Front ECU connector. Recheck for DTCs. If DTC 21 sets, go to next step. If DTC 21 does not set, replace Front ECU.
Disconnect Sun Roof ECU connector. Recheck for DTCs. If DTC 21 sets, replace ETACS ECU. If DTC 21 does not set, replace Sun Roof ECU. See SUN ROOF ECU under REMOVAL & INSTALLATION.

COMMUNICATION LINE IDENTIFICATION

Control Unit & Terminal No.

Joint Connector Terminal No. ⁽¹⁾

Wire Color

Column ECU - 3 ⁽²⁾

Blue/White

ETACS-ECU - 42 ⁽³⁾

Blue/White

Front-ECU - 17 ⁽⁴⁾

Blue/White

Sun Roof ECU - 10 ⁽⁵⁾

Blue/White

⁽¹⁾	See Fig 1 .

⁽²⁾	See Figure .

⁽³⁾	See Figure .

⁽⁴⁾	See Figure .

⁽⁵⁾	See Fig 2 .

Fig 1: Locating & Identifying Joint Connector

Courtesy of DAIMLERCHRYSLER CORPORATION

Fig 2: Identifying Sun Roof Motor Assembly & Power Window Switch Connector Terminals

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.