B1291

MULTIPLEX COMMUNICATION: MULTIPLEX COMMUNICATION SYSTEM: B1291, B1292: Short to B+ in Light System Communication Bus Malfunction
B1292 - Short to GND in Light System Communication Bus Malfunction

DESCRIPTION

When a +B or body ground short circuit is detected on the light system communication bus (BEAN), the light system communication bus (BEAN) is disabled and a DTC code is output.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK DIAGNOSTIC TROUBLE CODE (A ECU)





(a) Disconnect the A ECU connector and check for DTCs B1291 and B1292.

OK:

DTCs B1291 and B1292 are not output.

NOTICE:
Reconnect the connector before starting the next check.

HINT
* The A ECU in the light system bus represents the No. 1 junction block assembly (multiplex network rear ECU)
* If the result is as specified, the disconnected A ECU No. 1 junction block assembly (multiplex network rear ECU) is malfunctioning.

B -- REPLACE A ECU
A -- Continue to next step.

2. CHECK DIAGNOSTIC TROUBLE CODE (B ECU)





(a) Disconnect the A ECU and B ECU connectors and check for DTCs B1291 and B1292.

OK:

DTCs B1291 and B1292 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connectors before starting the next check.

HINT
* The B ECU in the door system bus represents one of the following: (cowl side junction block ECU LH, position control ECU and switch assembly (driver side), engine room No. 2 junction block, AFS ECU, combination switch assembly (windshield wiper switch).
* If the result is as specified, the disconnected B ECU (one of the ECUs from the above list) or the wire harness between the A ECU and B ECU is malfunctioning.

B -- CHECK DIAGNOSTIC TROUBLE CODE (C ECU)
A -- Continue to next step.

3. CHECK WIRE HARNESS BETWEEN A ECU AND B ECU





(a) Disconnect the B ECU connector and check for DTCs B1291 and B1292.

OK:

DTCs B1291 and B1292 are not output.

NOTICE:
Reconnect the connector before starting the next check.

HINT
If the result is as specified, the wire harness between the A ECU and B ECU is functioning normally but the disconnected B ECU is malfunctioning.

B -- REPAIR OR REPLACE WIRE HARNESS BETWEEN A ECU AND B ECU

A -- REPLACE B ECU

4. CHECK DIAGNOSTIC TROUBLE CODE (C ECU)





(a) Disconnect the B ECU and C ECU connectors and check for DTCs B1291 and B1292.

OK:

DTCs B1291 and B1292 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connectors before starting the next check.

HINT
* The C ECU in the light system bus represents the cowl side junction block RH, multiplex milt and telescopic ECU.
* If the result is as specified, the disconnected C ECU (cowl side junction block RH, multiplex tilt and telescopic ECU), mayday ECU or the wire harness between the B ECU and C ECU is malfunctioning.

B -- CHECK WIRE HARNESS BETWEEN GATEWAY ECU AND A ECU OR C ECU
A -- Continue to next step.

5. CHECK WIRE HARNESS BETWEEN B ECU AND C ECU





(a) Disconnect the C ECU connector and check for DTCs B1291 and B1292.

OK:

DTCs B1291 and B1292 are not output.

NOTICE:
Reconnect the connector before starting the next check.

HINT
If the result is as specified, the wire harness between the B ECU and C ECU is functioning normally but the disconnected C ECU is malfunctioning.

B -- REPAIR OR REPLACE WIRE HARNESS BETWEEN B ECU AND C ECU

A -- REPLACE C ECU

6. CHECK WIRE HARNESS BETWEEN GATEWAY ECU AND A ECU OR C ECU





(a) Check for a short-circuit in B+ or body ground.

(1) Disconnect the A ECU, C ECU and gateway ECU connectors.

(2) Measure the voltage and resistance of the wire harness side connectors.

Standard voltage:





Standard resistance:





HINT
* The A ECU in the door system bus represents the AFS ECU.
* The C ECU in the door system bus represents the luggage room junction block (rear junction block ECU).

NG -- REPAIR OR REPLACE WIRE HARNESS BETWEEN GATEWAY ECU AND A ECU OR C ECU

OK -- REPLACE NETWORK GATEWAY ECU