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Home >> Mercedes Benz >> 1988 >> 560SL >> Repair and Diagnosis >> Engine Performance >> System >> Cis-E System >> Trouble Shooting >> Testing With Impulse Counter >> Code 4, Airflow Sensor Position Indicator
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Code 4, Airflow Sensor Position Indicator

  1. CIS-E control unit connected, engine at idle and at operating temperature. Connect voltmeter negative lead to socket No. 7 and positive lead to socket No. 18 of socket box. Voltmeter should read 4.6-5.1 volts. If not within range, proceed to Code 8 testing procedures.
  2. Connect negative voltmeter lead to socket No. 7 and positive lead to socket No. 17. Voltmeter should read 0.55 to 0.95 volt. If not, check or replace airflow sensor position indicator or CIS-E control unit.
  3. Turn ignition "OFF". Unplug connector on airflow position indicator. Check resistance between pins one and 3 of connector. Ohmmeter should read 3600-4400 ohms. Move ohmmeter lead from pin 3 to pin 2 of connector and slowly deflect airflow sensor plate by hand. Resistance reading should increase continuously up to half of travel, then decrease again. If not, replace airflow sensor.
  4. Measure airflow sensor position indicator wiring harness resistance. Connect ohmmeter between socket No. 7 and wiring harness connector terminal No. one. Connect ohmmeter to socket No. 18 and wiring harness connector terminal No. 3. Connect ohmmeter between socket No. 17 and wiring harness connector terminal No. 2. All these should have a resistance of less than one ohm. If not, check for open circuit.
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