Electronic Idle Speed Control (190E 2.6L & 300 Series) Test

Connect Test Cable (103 589 00 63 00) to idle speed air valve and on-off ratio tester. Push IR 100% button. With engine at idle and at normal operating temperature, tester should read a minimum value of 36-50% at 650-750 RPM. If okay, test is complete. If tester reading is not as specified, proceed to next step.
If readout was 50-100%, check for air leak or air restriction. If readout was 0-35%, turn engine off. Disconnect plug from idle speed air valve. Briefly apply battery voltage to idle speed air valve. When idle speed air valve switches, a clicking sound should be heard or it should be felt with hand. If valve does not switch, replace idle speed air valve. If valve clicks or switching could be felt, proceed to next step.
To test voltage supply, turn ignition on. Voltage on terminal No. 2 of idle speed air valve plug should be about 12 volts. Test Red/White wire for continuity between terminal No. 1 and terminal No. 3 (of idle speed air valve plug) of CIS-E control unit plug. If continuity does not exist, repair open circuit. If continuity is present, proceed to next step.
Test input signals at coolant temperature sensor, airflow sensor position indicator, idle speed contact on throttle valve switch or CIS-E control unit.