DTC Troubleshooting: B1142 (5-door) - Honda Civic FC/FK 2016-2021

DTC Troubleshooting: B1142

DTC B1142: Door Multiplex Control Unit Lost Communication with Front Passenger's Power Window Switch (UART Line Open)

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A.

DTC Description	DTC
B1142 Door Multiplex Control Unit Lost Communication with Front Passenger's Power Window Switch (UART Line Open)

Problem verification:

Problem verification

?1.	Clear the DTCs with the HDS.

?2.	Turn the vehicle to the OFF (LOCK) mode and then the ON mode.

?3.

Check for DTCs with the HDS.

DTC Description	DTC
B1142 Door Multiplex Control Unit Lost Communication with Front Passenger's Power Window Switch (UART Line Open)

Is DTC B1142 indicated?


	YES

Go to step 2.


	NO

Intermittent failure, the system is OK at this time.?

Open wire check (LIN(P/W) line) 1:

Open wire check (LIN(P/W) line) 1

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.

Disconnect the following connectors.

Power window master switch 37P connector
Front passenger's power window switch 37P connector
Moonroof motor-control unit 14P connector (with moonroof)

?3.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Power window master switch 37P connector: disconnected Front passenger's power window switch 37P connector: disconnected Moonroof motor-control unit 14P connector (with moonroof): disconnected
Test point 1	Power window master switch 37P connector No. 36
Test point 2	Front passenger's power window switch 37P connector No. 34

Is there continuity?


	YES: Without moonroof

The LIN(P/W) wire is not open between power window master switch and front passenger's power window switch. Go to step 4.


	YES: With moonroof

The LIN(P/W) wire is not open between power window master switch and front passenger's power window switch. Go to step 3.


	NO

Repair an open or high resistance in the wire.?

Open wire check (LIN(P/W) line) 2:

Open wire check (LIN(P/W) line) 2

?1.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Power window master switch 37P connector: disconnected Front passenger's power window switch 37P connector: disconnected Moonroof motor-control unit 14P connector: disconnected
Test point 1	Power window master switch 37P connector No. 36
Test point 2	Moonroof motor-control unit 14P connector No. 12

Is there continuity?


	YES

The LIN(P/W) wire is not open between power window master switch and moonroof motor-control unit. Go to step 4.


	NO

Repair an open or high resistance in the wire.?

Shorted wire check (LIN(P/W) line):

Shorted wire check (LIN(P/W) line)

?1.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode Power window master switch 37P connector: disconnected Front passenger's power window switch 37P connector: disconnected Moonroof motor-control unit 14P connector (with moonroof): disconnected
Test point 1	Power window master switch 37P connector No. 36
Test point 2	Body ground

Is there continuity?


	YES

Repair a short to ground in the wire.?


	NO

The LIN(P/W) wire is not shorted to ground. Go to step 5.

Shorted wire check (LIN(P/W) line to power):

Shorted wire check (LIN(P/W) line to power)

?1.	Turn the vehicle to the ON mode.

?2.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode Power window master switch 37P connector: disconnected Front passenger's power window switch 37P connector: disconnected Moonroof motor-control unit 14P connector (with moonroof): disconnected
Test point 1	Power window master switch 37P connector No. 36
Test point 2	Body ground

Is there less than 0.2 V?


	YES

The LIN(P/W) wire is OK. Go to the front passenger's power window switch input test, and do the power and ground input tests. If the tests prove OK, substitute a known good front passenger's power window switch. If the DTC goes away, replace the original front passenger's power window switch. If the DTC is still present, replace the power window master switch.?


	NO

Repair a short to power in the wire.?