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Multiplex Control System: Overview Lexus GS II

Communication Devices 1 illustration ~870 words

DESCRIPTION & OPERATION

WARNINGDeactivate air bag system before performing any service operation. See AIR BAG RESTRAINT SYSTEMS article. DO NOT apply electrical power to any component on steering column without first deactivating air bag system. Air bag may deploy.

The multiplex control system is controlled and monitored by the body No. 1 and body No. 2 Electronic Control Units (ECUs). (Scheme 1) Other components in the system include

  1. A/C Control Assembly
  2. Air Bag Sensor Assembly
  3. Driver Door ECU
  4. Engine Control Module (ECM)
  5. Instrument Panel ECU
  6. Left Rear Door ECU
  7. Passenger (right front) Door ECU
  8. Right Rear Door ECU
  9. Tilt And Telescopic ECU

If equipped, system also includes

  1. Multi-Display ECU
  2. Power Seat ECU
  3. Sun Roof ECU

A bus cut relay is located inside of body No. 1 ECU and body No. 2 ECU. If communication bus is shorted, bus cut relay will disconnect affected portion of circuit. If no switch input change is received for 30 seconds, ECU interrupts communication to save battery power.

Scheme 1

Scheme 1
Scheme 1

Description

Code B1211 ( 11 ) sets when no communication is received from driver's door ECU for more than 10 seconds. Problem is in driver's door ECU or wiring harness.

Code B1212 ( 12 ) sets when no communication is received from passenger door ECU for more than 10 seconds. Problem is in passenger door ECU or wiring harness.

Code B1213 ( 13 ) sets when no communication is received from tilt and telescopic ECU for more than 10 seconds. Problem is in tilt and telescopic ECU or wiring harness.

Code B1214 ( 14 ) or B1215 ( 15 ) sets when communication bus is shorted to battery voltage ( 14 ) or ground ( 15 ). Bus cut relays in body No. 1 ECU and body No. 2 separate shorted portion of bus to prevent complete failure.

Code B1216 ( 16 ) sets when no communication is received from right rear door ECU for more than 10 seconds. Problem is in right rear door ECU or wiring harness.

Code B1217 ( 17 ) sets when no communication is received from left rear door ECU for more than 10 seconds. Problem is in left rear door ECU or wiring harness.

Code B1218 ( 18 ) sets when no communication is received from body No. 2 ECU for more than 10 seconds. Problem is in body No. 2 ECU or wiring harness.

If code sets when switch is operated, check switch continuity. If code sets when switch is not operated, switch is sticking. Check switches in order listed after each DTC. If switches are okay, check applicable wiring and connectors. See WIRING DIAGRAMS. Repair as necessary.

  1. B1221/21 DRIVER'S DOOR POWER WINDOW SWITCH. Driver's door power window switch. See POWER WINDOWS article.
  2. B1222/22 DRIVER'S DOOR LOCK SWITCH. Driver's door lock switch, lock cylinder lock/unlock switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  3. B1223/23 PASSENGER'S DOOR POWER WINDOW SWITCH, Power window switch. See POWER WINDOWS article. Door lock control switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  4. B1224/24 PASSENGER'S DOOR LOCK SWITCH. Passenger door lock switch, lock cylinder lock/unlock switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  5. B1225/25 RIGHT REAR DOOR POWER WINDOW SWITCH. Power window switch. See POWER WINDOWS article. Door lock control switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  6. B1226/26 LEFT REAR DOOR LOCK SWITCH. Power window switch. See POWER WINDOWS article. Door lock control switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  7. B1241/41 BODY NO. 1 ECU SWITCH CIRCUIT (TRUNK RELEASE). Trunk release switch, trunk lock cylinder lock/unlock switch. See POWER DOOR LOCKS, TRUNK LID & FUEL DOOR article.
  8. B1252/52 BODY NO. 2 ECU SWITCH CIRCUIT (STOPLIGHT). Stoplight switch. See CRUISE CONTROL SYSTEMS article.

Code B1242 ( 42 ) sets when short to ground is detected on remote keyless entry wiring. Problem is in wiring harness, remote keyless entry ECU or body No. 1 ECU.

B1244 ( 44 ) code is set when light sensor circuit problem is detected. Problem is in light sensor, wiring harness or body No. 2 ECU. If LEXUS hand-held tester is not available, start test at step 2).

B1255 ( 55 ) code is set when P1 switch failure (stuck on) is detected. P1 switch is located in shift lock control ECU. Problem is in P1 switch or wiring harness.

B1261 ( 61 ) code is set when no communication is detected from ECM for 10 seconds. Problem is in ECM or wiring harness.

B1262 ( 62 ) code is set when no communication is detected from A/C control assembly for 10 seconds. Problem is in A/C control assembly or wiring harness.

Code B1266 or B1267 sets when instrument panel communication bus is shorted to battery voltage (B1266) or ground (B1267). Bus cut relays in body No. 1 ECU and body No. 2 ECU separate shorted portion of bus to prevent complete failure.

B1271 ( 71 ) code is set when no communication is detected from instrument panel for 10 seconds. Problem is in instrument panel ECU or wiring harness.

B1272 ( 72 ) code is set when no communication is detected from power seat ECU for 10 seconds. Problem is in power seat ECU or wiring harness.

B1273 ( 73 ) code is set when no communication is detected from sun roof ECU for 10 seconds. Problem is in sun roof ECU or wiring harness.

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