DTC Troubleshooting: B1127
DTC B1127: Driver's Door Key Cylinder Switch Input Circuit Malfunction (Simultaneous input of lock and unlock signal)
DTC Description
DTC
B1127 Driver's door key cylinder switch input Circuit Malfunction (Simultaneous input of lock and unlock signal)
  

NOTE: Refer to the Electrical Wiring Diagrams for the location of the under-dash fuse/relay box connectors.

1.
Problem verification (driver's door key cylinder switch in the neutral position):

Problem verification (driver's door key cylinder switch in the neutral position)
?1.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Driver's Door Key Cylinder Switch(LOCK)
    
Driver's Door Key Cylinder Switch(UNLOCK)
    

Is either information indicator ON?

     
YES
     
     
     
Go to step 4.
     
NO
     
     
     
Go to step 2.
2.
Problem verification (driver's door key cylinder switch in the lock position):

Problem verification (driver's door key cylinder switch in the lock position)
?1.
With the driver's door key cylinder in the lock position, check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Driver's Door Key Cylinder Switch(LOCK)
    
Driver's Door Key Cylinder Switch(UNLOCK)
    

Are both information indicators ON?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
Intermittent failure, the system is OK at this time.
3.
Shorted wire check (DR KEY CYL UNLOCK to DR KEY CYL LOCK line):

Shorted wire check (DR KEY CYL UNLOCK to DR KEY CYL LOCK line)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Disconnect the following connector.

?3.
Connect terminals A and B with a jumper wire.


?4.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Driver's Door Key Cylinder Switch(LOCK)
    
Driver's Door Key Cylinder Switch(UNLOCK)
    

Are both information indicators ON?

     
YES
     
     
     
Repair a short between the wires.?
     
NO
     
     
     
The DR KEY CYL UNLOCK to DR KEY CYL LOCK wire is OK. Faulty driver's door key cylinder switch; replace the driver's door latch.?
4.
Determine possible failure area (driver's door latch, others):

Determine possible failure area (driver's door latch, others)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Disconnect the following connector.

?3.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
Driver's Door Key Cylinder Switch(LOCK)
    
Driver's Door Key Cylinder Switch(UNLOCK)
    

Is either information indicator ON?

     
YES
     
     
     
Go to step 5.
     
NO
     
     
     
Faulty driver's door key cylinder switch; replace the driver's door latch.?
5.
Shorted wire check (DR KEY CYL UNLOCK, DR KEY CYL LOCK lines):

Shorted wire check (DR KEY CYL UNLOCK, DR KEY CYL LOCK lines)
?1.
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

?2.
Disconnect the following connector.

?3.
Check for continuity between test points 1 and 2 individually.
Test condition
IG LOCK (0) or OFF mode
Driver's door latch 10P connector: disconnected
Under-dash fuse/relay box connector P (24P): disconnected
Test circuit
DR KEY CYL UNLOCK
Test point 1
Under-dash fuse/relay box connector P (24P) No. 4 (RED)
Test point 2
Body ground

Test circuit
DR KEY CYL LOCK
Test point 1
Under-dash fuse/relay box connector P (24P) No. 3 (PUR)
Test point 2
Body ground


Are there continuity?

     
YES
     
     
     
Repair a short to ground in the wire.?
     
NO
     
     
     
The DR KEY CYL UNLOCK and DR KEY CYL LOCK wires are OK. Faulty MICU; replace the under-dash fuse/relay box.?