Cranking Holding Function Circuit [12/2015 - 08/2016]: Description

WARNING: This page is about a different car, the 2016 Toyota Sienna. However, it is still accessible from the selected car via links, so may be relevant.

The cranking holding control system keeps energizing the ST relay from when the power management control ECU detects the starter signal from the ignition switch assembly until the power management control ECU performs a judgement of "Engine started".

When the power management control ECU detects the STSW signal, the power management control ECU outputs the ST relay drive signal (STAR signal) to the ST relay through the park/neutral position switch, and then, the engine is cranked. When the power management control ECU receives a stable engine speed signal (NE signal), more specifically, when the NE signal reaches a predetermined value, the power management control ECU stops outputting the STAR signal.

Also, the power management control ECU monitors the ST relay operating conditions based on the STA terminal voltage status.