Inspection Procedure

WARNING: This page is about a different car, the 2007 Lexus GX 470. However, it is still accessible from the selected car via links, so may be relevant.

CHECK WIRE HARNESS (MAYDAY ECU ASSEMBLY - MAYDAY BATTERY)

Fig 1: Identifying Mayday Battery & Mayday ECU Connector Terminals

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Disconnect the M16 ECU connector.
Disconnect the M19 battery connector.
Measure the resistance of the wire harness side connectors.
Standard resistance

RESISTANCE SPECIFICATION

Tester Connection	Specified Condition
M16-2 (BBI+) - M19-1 (BBO+)	Below 1 Ω
M16-9 (BBI-) - M19-2 (BBO-)	Below 1 Ω
M16-2 (BBI+) or M19-1 (BBO+) - Body ground	10 kΩ or higher
M16-9 (BBI-) or M19-2 (BBO-) - Body ground	10 kΩ or higher

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step

REPLACE MAYDAY BATTERY (BACKUP BATTERY)
1. Perform registration (See REGISTRATION ).
2. Check for DTC again.
  OK:
  
  No DTCs output.
OK: END

NG: Go to next step
REPLACE MAYDAY ECU ASSEMBLY
1. Replace the mayday ECU assembly (See REMOVAL ).
PERFORM REGISTRATION
1. Perform registration (See REGISTRATION ).
END