Multiplex Control Systems: Diagnosis Lexus LS III

SELF-DIAGNOSTICS

When diagnosing multiplex control system, perform BODY CONTROL ECU and OPEN DOOR INDICATOR LIGHT inspection procedures first to ensure DTCs can be retrieved. See PRELIMINARY INSPECTION .

Scheme 1

1. Check if Diagnostic Trouble Codes (DTCs) can be retrieved from body ECU. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-27213-S19311377262001010800000). If DTCs can be accessed, perform appropriate self-diagnostics. If DTCs cannot be accessed, go to next step.
2. Turn ignition off. Disconnect body ECU connector. (Scheme 1) Measure voltage between connector terminals No. 12 (Blue/Yellow wire) and No. 22 (White/Black wire). Battery voltage should be present. Check continuity between ground and connector terminals No. 22 (White/Black wire) and No. 11 (White/Black wire). Continuity should be present. Turn ignition on. Measure voltage between ground and connector terminals No. 2 (Red/Blue wire) and No. 13 (Gray wire). Battery voltage should be present. If voltages and continuity are to specification, go to next step. If voltages and continuity are not to specification, repair open or short circuit in wiring as necessary.
3. Check White/Green wire between body ECU connector terminal No. 7 and Data Link Connector 3. Repair wiring as necessary. If wiring is okay, replace body ECU.

Scan Tool Method

Multiplex self-diagnostic system DTCs are retrieved through Data Link Connector 3 (DLC3). DLC3 is located under left side of instrument panel. Connect scan tool to DLC3. Turn ignition on. Follow LEXUS or scan tool instructions to retrieve DTCs. See MULTIPLEX DIAGNOSTIC TROUBLE CODE (DTC) DEFINITION table. If DTC(s) is present, perform appropriate test. See DIAGNOSTIC TESTS .

DIAGNOSTIC TROUBLE CODE DEFINITIONS

MULTIPLEX DIAGNOSTIC TROUBLE CODE (DTC) DEFINITION

CLEARING DIAGNOSTIC TROUBLE CODES

Note. DTCs will be cleared from memory when DTC is normally retrieved.

DIAGNOSTIC TESTS