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Home >> Lexus >> 2019 >> UX 250h Base >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Anti-Theft Systems >> Smart Access System W/ Push-Button Start (Start Function) (Diagnostic Codes & Symptom Tests (1 Of 2)) (Hybrid) >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function, HV Model) >> Power Source Mode does not Change to ON (IG and ACC) [10/2018 - 08/2021] >> Description
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Power Source Mode does not Change to ON (IG and ACC) [10/2018 - 08/2021]: Description

When the power switch cannot be turned on (ACC) or on (IG), interior verification may be abnormal or there may be a malfunction in the ACC relay or IG relay circuit. If interior verification cannot be performed, the certification ECU (smart key ECU assembly) may be malfunctioning or communication may not be possible between the No. 1 indoor electrical key antenna assembly (front floor) or No. 2 indoor electrical key antenna assembly (rear floor) and the electrical key transmitter sub-assembly and Electrical key and TPMS receiver assembly.

When an electrical key transmitter sub-assembly is brought into the cabin, its key ID code is compared with the key ID code stored in the certification ECU (smart key ECU assembly). If these codes do not match, key verification will fail and the power switch will not be able to be turned on (ACC) or on (IG).

When a door is unlocked and an electrical key transmitter sub-assembly is brought into the cabin, the certification ECU (smart key ECU assembly) activates the indoor electrical key antenna assemblies to form the interior detection area. The electrical key transmitter sub-assembly then responds to the detection signals with its key ID code. This response signal is received by the Electrical key and TPMS receiver assembly and sent to the certification ECU (smart key ECU assembly).

RELATED DATA LIST AND ACTIVE TEST ITEMS

Problem Symptom Data List and Active Test
Power source mode does not change to on (IG) or on (ACC) Power Source Control 
  • Start Switch1
  • Start Switch2
  • IG Relay Monitor (Inside)
  • ACC Relay Monitor
  • IG Relay Monitor (Outside)
  • Latch Circuit
  • Power Supply Condition