B1271

MULTIPLEX COMMUNICATION SYSTEM: B1271: Combination Meter ECU Communication Stop

DTC B1271 - Combination Meter ECU Communication Stop

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.

WIRING DIAGRAM

INSPECTION PROCEDURE
HINT: When "+B or 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.

PROCEDURE

1. CHECK OPERATION
(a) 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 -- CHECK RESISTANCE OF COMMUNICATION LINE
NG -- Continue to next step.
2. INSPECT FUSE (ECU-B NO. 1, DOME)
(a) Remove the ECU-B No. 1 and DOME fuses from the fusible link block and instrument panel junction block.
(b) Measure the resistance of the fuses.
Standard resistance:
Below 1 Ohms
NG -- REPLACE FUSE
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (COMBINATION METER - BATTERY AND BODY GROUND)

(a) Disconnect the C8 and C9 meter connectors.
(b) Measure the voltage of the wire harness side connectors.
Standard voltage:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK RESISTANCE OF COMMUNICATION LINE
(a) Disconnect the A20 and G3 ECU connectors (with LEXUS navigation system).
(b) Disconnect the A20 and C4 ECU connectors (without LEXUS navigation system).

*1: with LEXUS Navigation System
*2: without LEXUS Navigation System
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE COMBINATION METER