Ignition Control Module. It is the switch/amplifier/interface upon which the ignition coils mount. They also receive their ground connections from it. The ICM serves as the junction point where the CMP and CKP connect to the PCM and help time the ignition primary switching. The ICM has a habit of growing corrosion on its top surface, and that interferes with ground connections and cooling. There is a large connector at the front of the ICM which is semi-exposed to the elements under the hood. All of that should be inspected, cleaned if necessary, and re-sealed with dielectric grease to keep moisture out.