Connect test cable to Bosch Lambda Control Tester (KDJE-P 600) and to idle speed air valve. Push IR 100% button. Engine should be at idle speed and operating temperature. Nominal value reading should be 27-29% at 670-770 RPM. If reading is correct, test is complete. If reading is not correct, go to next step.
If reading is higher or lower, adjust valve to nominal value or test microswitch. If reading is 0%, test voltage at plug of idle speed air valve. Connect multimeter between socket No. 2 and ground. If reading is not correct, repair wiring circuit. Reading should be 12 volts. If reading is correct, go to next step.
Measure resistances of idle speed air valve. Between terminals No. 2 and 3 or 2 and 1, reading should be 12 ohms. If not correct, replace idle speed air valve. If correct, test is complete.

NOTE: If voltage at sockets No. 1 and 3 (tested individually to ground) is 12 volts, check Brown ground wire from terminal No. 20 to ECU for continuity. Repair wiring or replace ECU as necessary.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Electronic Idle Speed Control

Use the Manual With the Right Hardware

When to See a Mechanic