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Home >> Nissan-Datsun >> 1985 >> Maxima SE >> Repair and Diagnosis >> Engine Performance >> System >> ECC CEC System >> Self-Diagnostic System >> Mixture Ratio Feedback System

Mixture Ratio Feedback System

  1. Make sure idle speed, engine operating temperature and ignition timing are normal. Make sure diagnosis mode lever is turned fully counterclockwise.
  2. Run engine at about 2000 RPM for 2 minutes under no-load. Make sure that Green inspection lamp on control unit goes on and off more than 5 times in 10 seconds while engine is running at 2000 RPM.
  3. If not, go to step 7). If okay, disconnect throttle valve switch harness connector. Race engine under no-load 2 or 3 times and run at idle speed. Inspection lamps should blink. If so, connect throttle valve switch connector. Test is complete. If not, go to next step.
  4. Turn off engine and remove air flow meter from vehicle. Drill a hole in plug which seals variable resistor of air flow meter and remove seal plug. Install air flow meter on vehicle. Start engine and warm up until indicator is at middle of gauge.
  5. Adjust idle mixture ratio by turning variable resistor of air flow meter so that inspection lamps blink simultaneously. If found to be not adjustable, replace air flow meter and return to step 1). If adjustable, go to next step.
  6. Turn off engine and remove air flow meter. Install a new seal plug into variable resistor hole. Install air flow meter to vehicle. Connect throttle valve switch harness connector and return to step 1).
  7. If inspection lamps failed to flash as specified in step 2), check exhaust gas sensor harness. Turn off engine and disconnect battery ground cable. Disconnect 16-pin connector from control unit.
  8. Disconnect exhaust gas sensor harness connector and connect terminal for exhaust gas sensor to ground with a jumper wire. Check for continuity between terminal 24 of 16 pin connector and ground metal of vehicle body. See Figure .
  9. If continuity does not exist, repair or replace harness and return to step 1). If continuity exists, disconnect cylinder head temperature harness connector. Connect a 2500 ohm resistor between harness connector terminals.
  10. Start engine and warm up until water temperature indicator points to the middle of the gauge. Race the engine 2 or 3 times under no-load, and run at idle speed.
  11. Check idle CO%. It should be .2-4.0%. After checking, disconnect the resistor from terminals of temperature sensor and reconnect connector to sensor. If CO was not okay, go to step 5). If okay, go to next step.
  12. Replace exhaust gas sensor and make sure inspection lamp goes on and off more than 5 times in 10 seconds when engine is run at 2000 RPM. If okay, return to step 1). If not, replace the ECCS control unit and return to step 1).
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