Multiplex Communication System - Diagnostics: Diagnosis Lexus GS III

HOW TO PROCEED WITH TROUBLESHOOTING

Perform troubleshooting in accordance with the procedure (Scheme 51)

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1. DIAGNOSIS SYSTEM (Scheme 53), each ECU of this vehicle is connected by communication bus and it transmits each signal by communication. This communication bus is self-diagnosed by Body No. 1 ECU and it memorizes DTC when it detects communication stop to ECU or communication bus +B short or GND short. There is a possibility that Body No. 1 ECU cannot self-diagnose accurately unless it doesn't work normal. So, please note that the troubleshooting of Body Electrical System should be done after confirming if Body No. 1 ECU and Open door indicator works normal by 2 "BASIC INSPECTION" described later. If DTC of ECU communication stop is output, there is a possibility of connector disconnection or 2 communication buses open. It will not become abnormal with only 1 communication bus open. If 2 communication buses are open at the position (Scheme 55), DTC of ECU communication stop between those 2 buses is output.
2. BASIC INSPECTION Basic inspection is for checking Body No.1 ECU normal operation. INSPECT BODY NO. 1 ECU Check Body No. 1 ECU operation. HINT: With this inspection Body No. 1 ECU CPU can be diagnosed if it works normal or not. CHECK: Check if the luggage compartment door opener works normal. OK: Go to step 3 (Using diagnosis check wire) Go to step 5 (Using hand-held tester) NG: Go to next step. Check luggage compartment door opener system (Except Body No. 1 ECU) (See «INSPECTION»(/lexus/gs/iii-2004-2007/remont/door-locks-anti-theft-systems/#power-door-lock-control-system) ). OK: Go to step 3 (Using diagnosis check wire) Go to step 5 (Using hand-held tester) NG: Repair or replace malfunction part. HINT: If repairing or replacing malfunction part, please repeat step 1. Check open door indicator light. CHECK: Check if open door Indicator light comes on when either door is open. HINT: If open door Indicator light is not turned on, DTC will not be output. OK: Go to step 4. NG: Repair the open door indicator light (See «INSPECTION»(/lexus/gs/iii-2004-2007/remont/gauges-instrument-panels/#combination-meter) ). HINT: If repairing or replacing malfunction part, please repeat step 3. DTC Check (Using diagnosis check wire) CHECK: Using diagnosis check wire. Using SST, connect terminals TC and CG of DLC3. SST 09843-18040 Turn the ignition switch ON. Read the DTC from the open door indicator light. HINT: As an example, the blinking patterns for codes; normal, 12 and 11 and 12 are (Scheme 58) Check the problem using the DTC table shown in «DIAGNOSTIC TROUBLE CODE CHART»(ref-229367-S24566888202006041400000). After completing the check, turn the ignition switch off, and disconnect terminals TC and CG. CHECK: Check the indicator blinking patterns. If normal code is indicated, the Body No.1 ECU is normal. OK: Go to Diagnosis trouble code chart (See «DIAGNOSTIC TROUBLE CODE CHART»(ref-229367-S24566888202006041400000) ). NG: Check the Body No.1 ECU power source (See «CIRCUIT INSPECTION»(/lexus/gs/iii-2004-2007/remont/communication-devices/#body-no1-control-system-diagnostics) ). DTC Check (Using hand-held tester) Prepare the hand-held tester. Connect the hand-held tester to DLC3. Turn the ignition switch ON and the hand-held tester main switch ON. Check the DTCs and note them down (When using hand held tester, see the hand-held tester's instruction book). CHECK: Check the DTC. If no DTC is indicated, the Body No.1 ECU is normal. If Body No.1 ECU is abnormal, you can not select the "Body No.1 ECU" in the hand-held tester screen. OK: Go to Diagnosis trouble code chart (See «DIAGNOSTIC TROUBLE CODE CHART»(ref-229367-S24566888202006041400000) ). NG: Check the Body No.1 ECU power source (See «CIRCUIT INSPECTION»(/lexus/gs/iii-2004-2007/remont/communication-devices/#body-no1-control-system-diagnostics) ).
3. DTC CLEARANCE A Multiplex DTC indicates that a problem has been detected in the Multiplex System. Once the problem is corrected and the system begins to operate as designed, the DTC will be cleared automatically. There is no need to manually clear a multiplex DTC using the hand-held tester.

DIAGNOSTIC TROUBLE CODE CHART

If a malfunction code is displayed during the DTC check, check the circuit listed for that code shown in DIAGNOSTIC TROUBLE CODE CHART .

DIAGNOSTIC TROUBLE CODE CHART

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HINT

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1. DTC 61, 66, 67 and 71 are not output through open door warning light on meter because of system itself.
2. DTC 21-26, 41 and 52 don't mean switch abnormal but notify how switch works. If DTC is not output when operating switch, it means failure of switch contact. If DTC is output when not opening switch, it means stick of switch.
3. When some of the DTC 14, 15, 66, 67 is output, the DTC of other ECU communication stop is also output. In this case, please repair DTC 14, 15, 66, 67 first. The following shows DTCs which are output when +B or GND short occurs on communication bus.

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CIRCUIT DESCRIPTION

This DTC is output when communication stops between driver door ECU and body ECU No. 1.

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1. Check driver door ECU. CHECK: Check if the driver door window glass auto up. HINT: With this inspection, the driver door ECU CPU can be diagnosed if it works normally or not. NG: Replace the driver ECU. OK: Go to next step.
2. Check wire harness. PREPARATION: Disconnect connector of Body ECU No. 2, "D24" of driver door ECU and "R12" of rear left door ECU. CHECK: Check continuity between terminals MPX1 of Body ECU No. 2 and MPX1 of driver door ECU. Check continuity between terminals MPX2 of driver door ECU and MPX1 of rear left door ECU. OK: There is a continuity in wire harness of both (a) and (b). or either (a) or (b). HINT: If there is OPEN in wire harness of either (a) or (b), please repair it. NG: Repair or replace wire harness. OK: Replace the driver door ECU.

This DTC is output when communication stops between front passenger door ECU and body ECU No. 1.

Scheme 78

This DTC is output when communication stops between tilt and telescopic ECU and Body No. 1 ECU.

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1. Check tilt and telescopic ECU. CHECK: Check the operation of the manual tilt and telescopic. HINT: With this inspection, the tile and telescopic ECU CPU can be diagnosed if it works normally or not. NG: Replace the tilt and telescopic ECU. OK: Go to next step.
2. Check wire harness. PREPARATION: Disconnect connector "C8" of airbag sensor assembly, "T5" of tilt and telescopic ECU, "C16" of steering pad switch, "G6" of gateway ECU and "A13" of A/C control assembly. CHECK: Check continuity between terminals MPX1 of airbag sensor assembly and MPX2 of tilt and telescopic ECU. Check continuity between terminals MPX1 of tilt and telescopic ECU and MPD1, MPD2 of gateway ECU. Check continuity between terminals MPX1 of tilt and telescopic ECU and MPX- of A/C amplifier. 3UZ-FE only: Check continuity between terminals MPX1 of steering pad switch and MPX2 of tilt and telescopic ECU. OK: Continuity exists in wire harness. HINT: If there is OPEN in wire harness of either (a), (b), (c) or (d), please repair it. NG: Repair or replace wire harness. OK: Replace the tilt and telescopic ECU.

If +B or GND short is detected on door system communication bus, instrument panel bus will be separated it by bus cut relays in Body ECU No.1 and Body ECU No.2. This is to prevent communication stop in the instrument panel bus. Or in other words, communication continues in instrument panel bus.

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This DTC is output when communication stops between rear right door ECU and body No.1 ECU.

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This DTC is output when communication stops between rear left door ECU and body No.1 ECU.

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This DTC is output when communication stops between Body ECU No. 2 and Body ECU No. 1.

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These DTC notify how switch works as follows

If DTC is not output when operating switch, it means failure of switch contact. If DTC is output when not operating switch, it means stick of switch. When something wrong is found by this diagnosis, inspect each switch. Then, replace the switch if there is a problem, or check the wire harness if there is no problem.

Scheme 86

These DTCs are output when a malfunction of pulse switch within power window motor is detected.

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These DTCs are output when a malfunction of limit switch within power window motor is detected.

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This DTC is output when GND short of RDA terminal is detected.

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1. Check wire harness. PREPARATION: Disconnect the connector of tuner and Body ECU No. 1. CHECK: Check the continuity between wire harness and body ground. OK: No continuity. NG: Repair or replace the wire harness. OK: Go to next step.
2. Check Body ECU No. 1. PREPARATION: Connect the connector of Body ECU No. 1. CHECK: Check the DTC. OK: B 1242/42 is not output. NG: Replace the Body ECU No. 1. OK: Replace the tuner.

This DTC is output when failure of light sensor circuit is detected.

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INSPECTION PROCEDURE

Using hand-held tester

1. Check light sensor. PREPARATION: Connect the hand-held tester to the DLC3. Turn ignition switch ON and hand-held tester main switch ON. CHECK: The value of the illumination rate should change in the following range when the light sensor is put in the light or covered by a hand OK: 0.8 ms - 22.0 ms HINT: This is the time to be taken for the light sensor to generate one circle of frequency according to the brightness. When not using hand-held tester (See «INSPECTION»(/lexus/gs/iii-2004-2007/remont/exterior-lights/#headlight-and-tailight-system) ). NG: Replace the light sensor. OK: Go to next step.
2. Check wire harness and connector between light sensor and Body No. 2 ECU. NG: Repair or replace wire harness or connector. OK: Replace the Body No. 2 ECU.

This DTC is output when communication stops between ECM and Body No. 1 ECU.

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This DTC is output when communication stops between A/C amplifier and Body ECU No. 1

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If +B or GND short is detected on instrument panel system communication bus, door bus will be separated it by bus cut relays in Body ECU No.1 and Body ECU No.2. This is to prevent communication stop in the door bus. Or in other words, communication continues in door bus.

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HINT

On the system structure point of view, this DTC cannot display meter. In case of checking DTC, please use hand held tester.

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1. Check the communication circuit inside ECM. PREPARATION: Disconnect the connector "E5" of ECM. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Replace the ECM. NG: Go to next step.
2. Check the communication circuit inside A/C Amplifier. PREPARATION: Connect the connector "E5" of ECM. Disconnect the connector "A13" of A/C amplifier. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Replace the A/C amplifier. NG: Go to next step.
3. Check the communication circuit inside gateway ECU. PREPARATION: Connect the connector "A13" of A/C amplifier. Disconnect the connector "G6" of gateway ECU. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Replace the gateway ECU. NG: Go to next step.
4. Check the communication circuit inside steering pad switch. HINT: Proceed to next step, when vehicle has no steering pad switch. PREPARATION: Connect the connector "G6" of gateway ECU. Disconnect the connector of "C16" steering pad switch. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output. OK: Replace steering pad switch. NG: Go to next step.
5. Check the communication circuit inside tilt and telescopic ECU. PREPARATION: w/ Steering pad switch: Connect the connector "C16" of steering pad switch. w/o Steering pad switch: Connect the connector "G6" of gateway ECU. Disconnect the connector "T5" of tilt and telescopic ECU. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Replace the tilt and telescopic ECU. NG: Go to next step.
6. Check the communication circuit inside airbag sensor assembly. PREPARATION: Connect the connector "T5" of tilt and telescopic ECU. Disconnect the connector "C8" of airbag of sensor assembly. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output. OK: Replace airbag sensor assembly. NG: Go to next step.
7. Check the communication circuit inside combination meter ECU. PREPARATION: Connect the connector "C8" airbag sensor assembly. Disconnect the connector "C13" of combination meter ECU. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Replace the combination meter ECU. NG: Go to next step.
8. Check the communication circuit inside Body ECU No. 2. PREPARATION: Connect the connector "C13" of combination meter ECU. Disconnect the connector "B6" of Body ECU No.2. Remove the Body ECU No.2 from Driver side J/B. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output. OK: Replace the Body ECU No. 2. NG: Go to next step.
9. Check for short circuit between combination meter ECU and Body ECU No. 2 PREPARATION: Disconnect the connector "C13" of combination meter ECU. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output. OK: Repair or replace the wire harness between combination meter ECU and Body ECU No. 2. NG: Go to next step.
10. Check short circuit between combination meter ECU and airbag sensor assembly. PREPARATION: Install the Body ECU No. 2 to driver side J/B. Connect the connector "B6" of Body ECU No. 2. Disconnect the connector "C8" of airbag sensor assembly. CHECK: Check DTC. OK: Code B1266 or B1267 is not output. OK: Repair or replace the wire harness between combination meter ECU and airbag sensor assembly. NG: Go to next step.
11. Check for short circuit between airbag sensor assembly and tilt and telescopic ECU. PREPARATION: Connect the connector "C13" of combination meter ECU. Disconnect the connector "T5" of tilt and telescopic ECU. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Repair or replace the wire harness between airbag sensor assembly and tilt and telescopic ECU. NG: Go to next step.
12. Check for short circuit between tilt and telescopic ECU, gateway ECU, steering pad switch and A/C amplifier. PREPARATION: Connect the connector "C8" of airbag sensor assembly. Disconnect the connector "A13" of A/C amplifier. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output. OK: Repair or replace the wire harness between tilt and telescopic ECU, gateway ECU, steering pad switch and A/C amplifier. NG: Go to next step.
13. Check for short circuit between A/C amplifier and ECM. PREPARATION: Connect the connector "T5" of tilt and telescopic ECU. Disconnect the connector "E5" of ECM. CHECK: Check the DTC. OK: Code B1266 or B1267 is not output OK: Repair or replace the wire harness between A/C amplifier and ECM. NG: Go to next step.
14. Check for short circuit between ECM and Body ECU No. 1. PREPARATION: Connect the connector "A13" of A/C amplifier. Disconnect the connector "B5" of Body ECU No. 1. CHECK: Check wire harness between ECM and Body ECU No. 1. NG: Repair or replace the wire harness between ECM and Body ECU No. 1. OK: Replace the Body ECU No. 1.

This DTC is output when communication stops between combination meter ECU and body No.1 ECU.

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This DTC is output when communication stops between power seat ECU and Body No.1 ECU.

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This DTC is output when communication stops between sliding roof ECU and Body ECU No. 1.

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This DTC is output when communication stops between airbag sensor assembly, combination meter ECU and tilt and telescopic ECU.

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This DTC is output when communication stops between steering pad switch and A/C amplifier.

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This DTC is output when communication stops between tilt and telescopic ECU, A/C amplifier and gateway ECU.

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See also:
• INSPECTION
• INSPECTION
• CIRCUIT INSPECTION
• INSPECTION