The power to the ABS, the idle control unit, and the lambda control unit is regulated by the xener diode in the OVP. The OVP itself is protected by the fuse on top of it. So if the fuse is bad or the OVP goes TU, all of these control units shut down. The ABS turns the light on, the idle control valve sits at open all the time which makes for a high idle.

The ICV is actually a frequency valve. The ICU adjusts the frequency that it closes to regulate the air to maintain a certain idle speed. But you can measure the output of the ICU in volts by sliding the connector back a bit and touching the probes carefully to the pins.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe