Focus FYDB ECU Problem - High Idle

**cheluakame** · 21st June, 2017, 07:08 PM

Hello again everyone.
Ok, got a Focus from 2000, with a 1.6 16v engine (FYDB).

Tested with autocom, and got IAC valve problem. Replace it with new one, but the problem is still there.

So, i started to test components. IAC valves are ok both, the problem is in ECU. More exactly i get -12 volts (straight) for IAC valve, instead of 0-5 volts (negative of course) PWM.

I've tooked down the ECU and opened it, no blown pieces, nothing wrong. Tried to measure some values and it's clear that somewhere, i've got a transistor or something that remains closed and offers always -12 volts.

Is here anyone who had this problme?

Could I find somewhere internal schematic of this ECU?

P.S. It's an LP4-335 , with 1S4F-12A650-BD code.

Thanks in advance.