ICU - Idle Control Unit
ICU/ISCU - Idle (Speed) Control Unit

The Idle Control Unit sends 4V to the Idle control valve during warm-up to maintain a smooth idle. If you do not see 4V at the Idle Control Valve this piece is probably why.

I have a 1984 380se. It wasn't revving over 1500rpm. I sent it in to a mechanic, who could not sort it out. I told him to tow it back to me this morning. This may sound weird, but I had a dream last night. I was standing in front of my car looking at the engine. My focus kept on being moved to the coil/ICU area. Anyway my mechanic called me to say he was stumped. That's when I told him to return the car. When it was back, and I told my mechanic that our working relationship was over (he had it 5 days!). I then remembered my dream. I went and bought a new ICU, fitted it in two minutes and Hallelujah, it started, revved magnificently, and drives like a dream. - Brad Jamison.

Second Generation cars:
Pull the passenger carpet and you will find a plastic floor near the firewall; use an extension with a 10mm socket to remove the plastic nut. The relay about the size of a pack of smokes and in the center is the ISCU. To the right you will see a carpeted piece - remove that to find the ECU that is to process data from the valve, ISCU, and O2 sensor as well. Its all there - remove the large a relay to the far left - very long one, that is the Becker alarm, it can be a problem with parasitic draw and horn blowing. - 281lxm@benzworld

First Generation cars:
It will be on the drivers side, behind false firewall. Module is about as big as an OG Gameboy. - corellian corvette@benzworld.

Ref: Frank Mallory's database and