Originally Posted by gingeRS
Originally Posted by richm
the iscv gets driven by a pulsed waveform (one terminal of valve has 12V supply, other terminal pulses low driven by pin34) - if you measure pin34 with a multimeter with respect to ground, what you will measure is the "average" voltage drive determined by the on/off ratio - as the valve drive reduces to close the valve, the average measured voltage will increase and conversely as the valve is driven open the average voltage measured at pin34 wil decrease
This may seem odd, but it's due to the active "on" signal being low.
so to summarise the voltage should start low, and raise as the engine warms up?
is it ok to measure the pins on the connector? with a DC multimeter.
if it doesnt change i can assume the valve is drive open ALL the time and there is afault somewhere?
yep, that's about right.
The actual voltage value you measure with a dc multimeter will indicate if the fault is with the ECU output driver, or elsewhere in the system.
A broken ECU driver stage would show as a consistently very low (approaching 0V) value. A strong pulsed drive signal, capable of holding the valve well open, will show as an average value somewhere appreciably above 0V.