2000 Yaris OCV Voltage Issue

[trim5678]

Hi, thanks for letting me join the forum. I'm a mechanic in the UK and I have an old 2000 Yaris (I think NCP10 variant?) in the shop at the moment. There is an issue with idling a little too high and the engine bogs down when you 'blip' the throttle. I have cleaned the throttle body, changed the plugs, changed the air filter, cleaned the MAF sensor, checked the OCV solenoid and cleaned the OCV filter below the solenoid.

I have found that the electrical feed to the OCV reads zero volts when the ignition is on and when the engine is running. I have applied a variable power supply to the OCV solenoid and fed it a range of voltages from 1-5V and the idle changes and then engine cuts out when the voltage reaches a little over 5V. This makes me think that the OCV is working, just not getting the correct voltage from the ECU?

My question for you guys is, what dictates the voltage supplied to the OCV? Are there sensors that will stop voltage flowing if they have failed?

I've checked the obvious things like broken wires to the OCV but there isn't anything obvious before they disappear into the loom.

Can anyone of you fine gentlemen help me out with this issue?

My thanks in advance!