DTC B1390: Power Tailgate Closer Function Error

WARNING: This page is about a different car, the 2009 Acura MDX, 2008 Acura MDX, and 2007 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

With the tailgate closed, pull the tailgate outer handle and wait for 10 seconds.
Turn the ignition switch to LOCK (0), and then back ON (II).
Clear the DTCs with the HDS.
Listen for the sound of the latch releasing.
Is there sound?

YES - Go to step 5.

NO - Go to Step 7.
Check for DTCs with the HDS.
Is DTC B1390 indicated?

YES - Go to step 6.

NO - Intermittent failure, the system is OK at this time. Check for loose or poor connections between the power tailgate control unit and the closer motor.
Check for DTCs with the HDS.
Are DTCs B1380, B1381, B1382, B1383, and/or B1384 also indicated?

YES - Troubleshoot the indicated DTCs.

NO - Replace the power tailgate control unit and recheck the system.
Turn the ignition switch to LOCK (0).
Open the tailgate.
Disconnect the 2P connector from the power tailgate closer motor.
Disconnect power tailgate control unit connector B (20P).
Check for continuity between the power tailgate control unit connector B (20P) No. 1 and No. 2 terminals and the power tailgate closer motor 2P connector No. 1 and No. 2 terminals respectively.

Fig 1: Identifying Continuity Between No. 1 And No. 2 Terminals And No. 1 And No. 2 Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Go to step 12.

NO - Repair open in the wire.
Measure the voltage between the power tailgate control unit connector B (20P) No. 12 terminal and body ground.

Fig 2: Identifying Voltage Between Power Tailgate Control Unit Connector B (20P) No. 12 Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES - Go to step 14.

NO - Check for No. 6 (20 A) fuse in the rear fuse/ relay box. If the fuse is OK, check for an open in the wire between the rear fuse/relay box and power tailgate control unit.
Disconnect power tailgate control unit connector A (5P).
Check for continuity between the power tailgate control unit connector A (5P) No. 4 terminal and body ground.

Fig 3: Identifying Continuity Between Power Tailgate Control Unit Connector A (5P) No. 4 Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Go to step 15.

NO - Repair open in the wire or poor ground (G701).
Turn the tailgate lock latch to the fully-closed position using a screwdriver.
Reconnect the power tailgate closer motor 2P connector.
Connect battery power to the power tailgate control unit connector B (20P) No. 2 (or No. 1) terminal and ground the No. 1 (or No. 2) terminal momentarily.

Fig 4: Identifying Battery Power To Power Tailgate Control Unit Connector B (20P) No. 2 (Or No. 1) Terminal And Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Does the motor run smoothly?

YES - Replace the power tailgate control unit.

NO - Go to step 18.
Reconnect the 6P connector to the power tailgate closer unit.
Check for continuity between the power tailgate control unit connector B (20P) No. 1 and No. 2 terminals and body ground respectively.

Fig 5: Identifying Continuity Between Power Tailgate Control Unit Connector B (20P) No. 1 And No. 2 Terminals And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Go to step 20.

NO - Go to step 22.
Disconnect the 6P connector from the power tailgate closer unit.
Check for continuity between the power tailgate control unit connector B (20P) No. 1 and No. 2 terminals and body ground respectively.

Fig 6: Identifying Continuity Between Power Tailgate Control Unit Connector B (20P) No. 1 And No. 2 Terminals And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Repair short in the wire.

NO - Replace the power tailgate closer unit.
Check for continuity between the power tailgate control unit connector B (20P) No. 9 terminal and body ground.

Fig 7: Identifying Continuity Between Power Tailgate Control Unit Connector B (20P) No. 9 Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Repair short in the wire.

NO - Check for No. 6 (20 A) fuse in the rear fuse/ relay box. If the fuse is OK, check for an open in the wire between the rear fuse/relay box and power tailgate control unit.