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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 110 (Stop And Start System - Diagnostic Codes) >> Stop And Start System >> DTC P1644-00: ECU Malfunction (Starter Circuit) [10/2022 - ] >> Typical Malfunction Thresholds

Typical Malfunction Thresholds

WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.
CASE 1, CASE2, CASE5

Engine stop and start ECU starter relay voltage Higher than [Battery voltage x 0.44] V
CASE 3

Either of the following conditions (a) or (b) is met -
(a) Engine stop and start ECU starter relay voltage [Battery voltage x 0.44] V or less
(b) Engine stop and start ECU starter relay voltage [Battery voltage x 0.88] V or higher
CASE 4

Engine stop and start ECU starter relay voltage Less than [Battery voltage x 0.88] V
CASE 6

Engine stop and start ECU starter relay terminal voltage level Low
CASE 6

Starter relay overcurrent Detected