Lexus Link System: Diagnosis Lexus LS III

HOW TO PROCEED WITH TROUBLESHOOTING

Note. This ECU is connected to the multiplex communication system. Therefore, be sure to check that there is no troubles in the multiplex communication system before performing the troubleshooting.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

LEXUS LINK SYSTEM DIAGNOSTIC TROUBLE CODES

Note. After all of the instruction messages have been provided, the voice of "Diagnostic complete" follows.

Scheme 45

Scheme 46

1. CONNECTORS (Scheme 45): Identifying ECU Connector Terminals
2. WIRING DIAGRAMS (Scheme 46): ECU Wiring Diagrams

CIRCUIT DESCRIPTION

This DTC is output when the Mayday ECU detects an open circuit of the GPS antenna.

INSPECTION PROCEDURE

Replace the GPS antenna.

This DTC is output when any of the Mayday switches is turned ON for 15 sec. or more and this condition is judged as a stuck switch.

Note that this DTC is output even though it is kept pressed intentionally.

Mayday Switch Wiring Diagram (Button Module Failure). Scheme 47

Scheme 48

1. Check the Mayday switch. PREPARATION: Disconnect the Mayday switch connector. CHECK: MAYDAY SWITCH CONNECTORS TERMINALS CONTINUITY Switch position Tester connection Specified condition Service Play back Record 1 - 2 Continuity Emergency Volume UP Volume DOWN 2 - 3 Continuity (Scheme 48): Identifying Mayday Switch Connector Terminals OK: There is a continuity when switch is pressed, and no continuity when not pressed. NG: Replace the Mayday switch. OK: Go to next step.
2. Check for open and short circuit in harness and connector between Mayday ECU and Mayday switch. NG: Replace or repair wire harness connector. OK: Replace the Mayday ECU.

When communication between the Mayday ECU and the transceiver is disabled, this DTC output. When power is not supplied to the transceiver, this DTC is also output because the communication is not possible.

Mayday ECU Wiring Diagram (Transceiver Failure). Scheme 49

1. Check for open and short circuit in harness and connector between Mayday ECU and transceiver. NG : Replace or repair wire harness connector. OK : Replace the transceiver. NOTE: If DTC is not cleared even though the transceiver is replaced, replace the Mayday ECU.

This DTC is output when there is a failure in the Mayday ECU. In this case, replace the Mayday ECU.

Replace the Mayday ECU.

The Mayday ECU monitors the backup battery voltage at terminal SUB BATT. When the voltage drops, this DTC is output. If the battery is normal and recharged with the ignition switch ON, the DTC will be cleared.

Mayday ECU Wiring Diagram (Back-Up Battery Failure). Scheme 50

1. Check the back-up battery. CHECK: With the ignition switch ON or the engine running, check whether or not this DTC is output again after several hours. OK: DTC is not output. OK : Temporary voltage drop. (electric discharge) No problem. NG : Go to next step.
2. Check for open and short circuit in wire harness and connector between Mayday ECU and back-up battery. NG : Replace or repair wire harness connector. OK : Replace the back-up battery. NOTE: If DTC is not cleared even though the battery is replaced, replace the Mayday ECU.

This DTC is output when communication from the AIRBAG ECU is interrupted for10 sec. or more. In this case, possible causes are communication interruption from the AIRBAG ECU, a failure in the accessory bus buffer or a break of the harness between the accessory bus buffer and the Mayday ECU.

Mayday ECU Wiring Diagram (Loss Of BEAN Communication). Scheme 51

1. Check the DTC. (gateway system) CHECK: Check whether or not "B1281: AIRBAG ECU Communication Stop" or "B1275: Accessory Bus Buffer Communication Stop" is detected in the Gateway ECU. OK: DTC is not output. NG : Proceed troubleshooting for each DTC. OK : Go to next step.
2. Check for open and short circuit in wire harness and connector between Mayday ECU and accessory bus buffer. NG : Replace or repair wire harness connector. OK : Replace the Mayday ECU. NOTE: If DTC is not cleared even though the Mayday ECU is replaced, replace the Accessory Bus Buffer.