Preparation For Checks
NOTE:
The frequency valve is operated by pulsating voltage from the electronic control unit. By measuring this signal, certain functions of the system can be tested. A voltmeter is used for Mercedes-Benz.
- Remove cap from diagnostic plug connector (rear of left fender panel). Connect positive lead of voltmeter to battery and negative lead to pin 3 of diagnostic plug.
- Start engine and run until warm. Disconnect oxygen sensor and observe meter needle (should not fluctuate). Place a piece of tape on meter face to indicate 50% position.