B1142

DTC Troubleshooting: B1142

DTC B1142:

Door Multiplex Control Unit Lost Communication With Other Units (UART communication error)

NOTE:

- If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A Troubleshooting - B-CAN System Diagnosis Test Mode A.
- Before troubleshooting, make sure the No. 16 (7.5 A), No. 20 (20 A) and No. 24 (20 A) fuses in the driver's under-dash fuse/relay box are OK.

1. Clear the DTCs with the HDS.

2. Turn the ignition switch to LOCK (0), and then back to ON (II).

3. Open and close all power windows by using the power window master switch.

4. Check for DTCs with the HDS.

Is DTC B1142 indicated?

YES -

Go to step 5.

NO -

Intermittent failure, the system is OK at this time. Check for loose or poor connections.

5. Turn the ignition switch to LOCK (0).

6. Disconnect these items:

- Power window master switch 37P connector

- Front passenger's power window switch 37P connector

- Moonroof control unit/motor 14P connector

7. Check for continuity between power window master switch 37P connector terminal No. 27 and front passenger's power window switch 37P connector terminal No. 29.





Is there continuity?

YES -

Go to step 8.

NO -

Repair an open or high resistance in the UART wire.

8. Check for continuity between power window master switch 37P connector terminal No. 27 and moonroof control unit/motor 14P connector terminal No. 11.





Is there continuity?

YES -

Go to step 9.

NO -

Repair an open or high resistance in the UART wire.

9. Check for continuity between power window master switch 37P connector terminal No. 27 and body ground.





Is there continuity?

YES -

Repair a short to ground in the UART wire.

NO -

Go to step 10.

10. Reconnect the power window master switch 37P connector.

11. Turn the ignition switch to ON (II).

12. Measure the voltage between power window master switch 37P connector terminal No. 27 and body ground.





Is there less than 0.2 V?

YES -

Go to the front passenger's power window switch input test, and do all the power and ground input tests Front Passenger's Power Window Switch Input Test. 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 Front Passenger's Power Window Switch Replacement. If the DTC is still present, replace the power window master switch Power Window Master Switch Replacement.

NO -

Repair a short to power in the UART wire.