Inspection Procedure

WARNING: This page is about a different car, the 2008 Lexus LS 600hL. However, it is still accessible from the selected car via links, so may be relevant.

CHECK HARNESS AND CONNECTOR (MAYDAY ECU - MAYDAY BATTERY)

Disconnect the R23 ECU connector.
Disconnect the S50 battery connector.
Measure the resistance according to the value(s) in the table below.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Condition	Specified Condition
R23-2 (BBI+) - z53-1 (BBI+)	Always	Below 1 Ω
R23-9(BBI-) - z53-2 (BBI-)	Always	Below 1 Ω
R23-2 (BBI+) or z53-1 (BBI+) - Body ground	Always	10 kΩ or higher
R23-9 (BBI-) or z53-2 (BBI-) - Body ground	Always	10 kΩ or higher

Fig 1: Checking Harness And Connector (Mayday ECU - Mayday Battery)

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR THEN CLEAR HISTORIC DTC

OK: Go to next step

REPLACE MAYDAY BATTERY (BACKUP BATTERY)
1. Replace the mayday battery (see REMOVAL ).
2. Perform registration (see REGISTRATION ).
3. Check for DTC again (see DTC CHECK / CLEAR ).
  OK: No DTCs output.
  
  NG: REPLACE MAYDAY ECU THEN PERFORM REGISTRATION
  
  OK: END (MAYDAY BATTERY IS FAULTY; CLEAR HISTORIC DTC)