Maybe I can clear some of this up
- A 2-wire (Bosch type) ISCV requires a switched 12V supply and a connection to one PWM capable ECU aux output.
- A 3-wire Toyota (4AGE 20V type) ISCV requires a switched 12V supply and connection to two PWM capable ECU outputs.
- ECU aux outs are only capable of switching a few amps to ground, and that will be fine for an ISCV. However, for switching higher currents like cooling fans, a relay must be interposed to protect the aux out from overload.
- To drive your 2-wire ISCV you will need to program the ECU to vary the PWM duty cycle according to engine cooling water temperature. There should be a 2D table you can call up. A PWM frequency of around 200Hz should work.
In general, the ECU does not supply 12V for any accessories. It switches 12V to ground to control relays, solenoids and other low current control components. The maximum current ratings for PWM capable and non-PWM capable outputs will be set down in the documentation for your ECU.
Cheers... jondee86
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