B1271 Combination meter assembly communication stops

DESCRIPTION

This DTC is detected when communication between the combination meter assembly (meter ECU) and multiplex network gateway ECU stops for more than 10 seconds.

DTC No.	DTC Detection Condition	Trouble Area
B1271	Combination meter assembly communication stops	Combination meter assembly (meter ECU) Wire harness

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

When "+B of GND short malfunction of communication bus" DTCs (B1266 and B1267) are detected at the same time as "communication stop" DTC B1271, repair the "+B or GND short malfunction of communication bus" DTCs first.

1. CHECK OPERATION

1. Check that the tachometer can operate properly while the engine is idling.

   HINT:

   With this inspection, the combination meter CPU can be diagnosed if it works normally or not.

   OK:

   Tachometer operates properly while engine is idling.
   

OK	Go to step 4

NG

2. INSPECT FUSE (ECU-B No.1, DOME)

1. Remove the ECU-B No.1 and DOME fuses from the fusible link block and instrument panel junction block.

2. Measure the resistance of the fuses.

   Standard resistance:

   Below 1 Ω
   

NG	REPLACE FUSE

OK

3. CHECK WIRE HARNESS (COMBINATION METER - BATTERY AND BODY GROUND)

1. Disconnect the C8 and C9 meter connectors.

2. Measure the voltage of the wire harness side connectors.

   Standard Voltage:

   Tester Connection	Specified Condition
   C8-15 (B) - Body ground	10 to 14 V
   C8-16 (B) - Body ground	10 to 14 V

3. Measure the resistance of the wire harness side connectors.

   Standard Resistance:

   Tester Connection	Specified Condition
   C9-1 (E) - Body ground	Below 1 Ω

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4. CHECK RESISTANCE OF COMMUNICATION LINE

1. Disconnect the A24 and G1 ECU connectors (w/ LEXUS navigation system).

2. Disconnect the A24 and C4 ECU connectors (w/o LEXUS navigation system).
   

3. Measure the resistance of the wire harness side connectors.

   Standard resistance:

   Tester Condition	Specified Condition
   C9-4 (MPX+) - A24-24 (MPX1)	Below 1 Ω
   C8-5 (MPX-) - C4-12 (MPX-) (*2)	Below 1 Ω
   C8-5 (MPX-) - G1-13 (MPI2) (*1)	Below 1 Ω

   *1: w/ LEXUS Navigation System*2: w/o LEXUS Navigation System

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK
REPLACE COMBINATION METER