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Home >> Lexus >> 2003 >> LS 430 >> Repair and Diagnosis >> External Pages >> Different car >> Section 217 (Engine Controls - System & Component Testing) >> Computerized Engine Controls >> Engine Control Module (ECM) Power Source Circuit (Ignition On) >> Circuit Description
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Circuit Description

WARNING: This page is about a different car, the 2003 Lexus GX 470. However, it is still accessible from the selected car via links, so may be relevant.

When ignition switch is turned on, 9-14 volts is applied to terminal IGSW at ECM. EFI relay control circuit in ECM then sends a signal to terminal MREL at ECM to switch EFI relay on. This signal causes current to flow to coil, closing contacts of EFI relay and supplying power to terminal +B of ECM. If ignition switch is turned off, ECM continues to switch on EFI relay for a maximum of 2 seconds for initial setting of throttle valve.

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