SERVICE MANUAL
  Applies to: Hyundai Coupe/Tiburon 1998-2000
GROUP
Fuel System MFI Control System
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HEATED OXYGEN SENSOR (HO2S) - II 

The heated oxygen sensor senses the oxygen concentration in the exhaust gas and, converts it into a voltage which is sent to the ECM. The heated oxygen sensor outputs about 800mV when the air fuel ratio is richer than the theoretical ratio and outputs about 100mV when the ratio is leaner (higher oxygen concentration in exhaust gas.) The ECM controls the fuel injection ratio based on this signal so that the air fuel ratio is maintained at the theoretical ratio. The oxygen sensor has a heater element which ensures the sensor performance during all driving condition.

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DTC - P1123, P1124, P1127, P1128 (AIR-FUEL CONTROL) 
TROUBLESHOOTING HINTS

When the lean/rich period is above 2.6 seconds in the condition that fully warm-up engine is 2,000 - 3,000 r.p.m. and engine is above middle load.

TROUBLESHOOTING HINTS
  1. If the heated oxygen sensor is defective, abnormally high emissions may occur.

  1. If the heated oxygen sensor check has been normal, but the sensor output voltage is out of specification, check the following items related to the air fuel ratio control system.

    • Faulty injector.
    • Air leaks in the intake manifold.
    • Faulty mass air flow sensor, EVAP valve and engine coolant temperature sensor.
    • Wiring connection problem.
  1. When 02 sensor output voltage is maintained as following for above 50 sec.

    • Upstream: 0.4V - 0.6V
    • Downstream: 0.4V - 0.5V
USING VOLTMETER
Check item
Check condition
Engine condition
Test specification
Heated oxygen sensor output voltage.(Heated oxygen sensor side connector No. 2 or ECM harness side connector
Warm-up.
When decelerate suddenly from 4,000 rpm.
'A' 200 mV or lower.
When engine is suddenly raced.
'B' 600-1,000 mV.
Heater resistance
Cooling (22°C)
Key, OFF
2.1 ± 0.4OHM
NOTE
If you release the accelerator pedal suddenly with the engine running about 4000 rpm, the fuel supply will be stopped for a while. When you suddenly press the accelerator pedal, the voltage will reach `B' range. Then, when you let the engine idle again, the voltage fluctuates between `A' and `B' range. In this case, the O2 sensor can be determined as good
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DTC - P1123, P1124, P1127, P1128 (AIR-FUEL CONTROL) 
TROUBLESHOOTING HINTS

Air/Fuel ratio stays rich or lean longer than specified period because of system malfunction

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CIRCUIT DIAGRAM 
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HARNESS INSPECTION PROCEDURE 
SENSOR INSPECTION
NOTE
  1. Before checking, warm up the engine until the engine coolant temperature reaches 80 to 95°C (176 to 205°F).
  2. Use an accurate digital voltmeter.
    • Replace the oxygen sensor if there is a malfunction.
  1. Disconnect the heated oxygen sensor connector, and measure the resistance between terminal 3 and terminal 4.

    Standard value
    Temperature °C(°F)
    Resistance O
    400 (752)
    30 or more
  1. Replace the oxygen sensor if there is a malfunction

    TORQUE SPECIFICATION
    Heated oxygen sensor 50-60 Nm ( 500-600 kg·cm, 37-44 lb·ft )