DTC B1128: Driver's Door Lock Switch Signal Error (LOCK/UNLOCK)

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch OFF, and then back ON (II).
Operate the driver's door lock switch LOCK/UNLOCK several times.
Check for DTCs with the HDS.
Is DTC B1128 indicated?

YES -Go to step 5.

NO -Intermittent failure. The driver's door lock system is OK at this time.
With the driver's door lock switch in the neutral position, select KEYLESS from the HDS and enter the DATA LIST.
Check the ON/OFF information of the DRIVER'S DOOR LOCK SWITCH (LOCK) and DRIVER'S DOOR LOCK SWITCH (UNLOCK) in the DATA LIST.
Are both information indicators OFF?

YES -Go to step 12.

NO -Go to step 7.
Disconnect the driver's power window switch 22P connector.
Check the ON/OFF information of the DRIVER'S DOOR LOCK SWITCH (LOCK) and DRIVER'S DOOR LOCK SWITCH (UNLOCK) in the DATA LIST.
Are both information indicators OFF?

YES -Faulty door lock switch; replace the driver's power window switch.

NO -Go to step 9.
Turn the ignition switch OFF.
Disconnect the under-dash fuse/relay box connector T (34P).
Check for continuity between the No. 28 (LOCK) and No. 27 (UNLOCK) terminals of the under-dash fuse/relay box connector T (34P) and body ground.

Fig 1: Checking Continuity Between 28 (LOCK) And 27 (UNLOCK) Terminals Of Under-Dash Fuse/Relay Box Connector T (34P) And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Are there continuity?

YES -Repair a short in the LOCK or UNLOCK wire.

NO -Faulty MICU, replace the under-dash fuse/relay box.
Turn the ignition switch OFF.
Disconnect the power window master switch 22P connector.
Disconnect under-dash fuse/relay box connector T (34P).
Check for continuity between the No. 28 (LOCK) and No. 27 (UNLOCK) terminals of the under-dash fuse/relay box connector T (34P).

Fig 2: Checking Continuity Between 28 (LOCK) And 27 (UNLOCK) Terminals Of Under-Dash Fuse/Relay Box Connector T (34P)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short in the wire between the LOCK and UNLOCK wires.

NO -Substitute a known-good power window master switch, and recheck. If the symptom/indication goes away, replace the original power window master switch. If not, the MICU is faulty, replace the under-dash fuse/relay box.