Hyundai Coupes/Sedans 1986-1993 Repair Guide

Component Testing

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ELECTRONIC CONTROL UNIT (ECU)



See Figure 1

Testing

The only way to test the ECU is to replace if with a known-good unit and check to see if symptom persists.

Removal & Installation

  1. Disconnect the negative battery cable.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: The ECU is mounted under the drivers side of the instrument panel-Scoupe shown, others similar

  1. Disconnect the electrical connectors to the ECU.
  2.  
  3. Remove the 2 screws that secure the ECU and remove the ECU.
  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

COOLANT TEMPERATURE SENSOR



See Figure 2

Testing
  1. Disconnect the electrical connectors from the coolant temperature sensor.
  2.  



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Fig. Fig. 2: Coolant temperature sensor diagram

  1. Remove the coolant temperature sensor from the intake manifold.
  2.  
  3. Stick the sensing portion of the sensor in water and connect an ohmmeter to the terminals and check resistance.
  4.  
  5. With the water temperature at 32°deg;F (0°deg;C), the resistance should be 5.9 kilo-ohms. With the water temperature at 68°deg;F (20°deg;C), the resistance should be 2.5 kilo-ohms. With the water temperature at 104°deg;F (40°deg;C), the resistance should be 1.1 kilo-ohms. With the water temperature at 176°deg;F (80°deg;C), the resistance should be 0.3 kilo-ohms.
  6.  
  7. If the resistance is not within specifications, replace the sensor.
  8.  
  9. Install the coolant sensor and connect the electrical connectors. Connect the negative battery cable.
  10.  

THROTTLE POSITION SENSOR



See Figure 3

Testing
  1. Loosen the accelerator cable.
  2.  
  3. Loosen speed adjusting screw No. 1 and No. 2 enough to close the throttle valve completely. Record the number of turns to loosen.
  4.  
  5. Connect voltmeter (digital type) between terminals No. 2 and No. 3 of the TPS connector pins.
  6.  

Do not disconnect the TPS connector from the chassis harness.

  1. Turn the ignition switch ON (engine will not start) and measure the TPS voltage. The voltage should read 250 millivolts.
  2.  
  3. If the output voltage is not correct, turn the TPS body to adjust to specification. Turning the TPS body clockwise increases the output voltage
  4.  
  5. Turn the ignition switch OFF .
  6.  
  7. Tighten speed adjusting screws the same number of turns as loosened.
  8.  
  9. Adjust the accelerator cable free-play.
  10.  
  11. Start the engine and check that the idle speed is correct.
  12.  



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Fig. Fig. 3: TPS connector terminal identification

OXYGEN SENSOR (FEDERAL)



Testing

See Figure 4

  1. Warm the engine to normal operating temperature.
  2.  



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Fig. Fig. 4: Testing the oxygen sensor

  1. Disconnect the oxygen sensor connector and connect a voltmeter to the sensor connector terminal of the oxygen sensor.
  2.  
  3. While increasing the engine rpm, measure the sensor output voltage.
  4.  
  5. As the rpm increase, the voltage should read approximately 0.6 volts. If not within specifications, replace the oxygen sensor.
  6.  

Removal and Installation
  1. Disconnect the electrical connector to the oxygen sensor.
  2.  
  3. Remove the oxygen sensor from the exhaust manifold.
  4.  
  5. To install, replace sensor and tighten to 29-36 ft. lbs. (40-50 Nm). Connect connector to sensor.
  6.  

OXYGEN SENSOR (CALIFORNIA)



Testing
  1. Warm the engine to normal operating temperature.
  2.  
  3. Disconnect the oxygen sensor connector and measure the resistance between terminals No. 3 and No. 4 . The resistance should measure 30 ohms or more at 752°deg;F (400°deg;C).
  4.  
  5. While increasing the engine rpm, measure the sensor output voltage between terminals No. 1 and No. 2 .
  6.  
  7. As the rpm increase, the voltage should read approximately 0.6 volts. If not within specifications, replace the oxygen sensor.
  8.  

Removal and Installation
  1. Disconnect the electrical connector to the oxygen sensor.
  2.  
  3. Remove the oxygen sensor from the exhaust manifold.
  4.  
  5. To install, replace sensor and tighten to 29-36 ft. lbs. (40-50 Nm). Connect connector to sensor.
  6.  

VACUUM SWITCH



Testing

See Figure 5

The vacuum switch can only be checked using the Hyundai FBC tester.



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Fig. Fig. 5: Testing the vacuum switch

  1. Connect FBC tester to the ECU harness connector at terminal No. 13 .
  2.  
  3. Set the select switch to the A mode and check switch to 6 .
  4.  
  5. With the ignition turned to the ON position and the engine not running, the meter should read 9-13 volts.
  6.  
  7. With the engine warm and at idle, the reading should be 0-0.6 volts.
  8.  

FEEDBACK SOLENOID VALVE



Testing

The Feedback solenoid valve can only be checked using the Hyundai FBC tester.

  1. Connect FBC tester to the ECU harness connector at terminal No. 1 .
  2.  
  3. Set the select switch to the B mode and check switch to 2 .
  4.  
  5. With the ignition turned to the ON position and the engine not running, the meter should read 11-13 volts.
  6.  
  7. With the engine warm and at idle, the reading should be 2-12 volts.
  8.  

SLOW CUT SOLENOID VALVE



Testing

The Slow cut solenoid valve can only be checked using the Hyundai FBC tester.

  1. Connect FBC tester to the ECU harness connector at terminal No. 9 .
  2.  
  3. Set the select switch to the B mode and check switch to 7 .
  4.  
  5. With the engine idling, the meter should read 0-0.6 volts.
  6.  
  7. Upon quick deceleration from above 4000 rpm to idle, the reading should momentarily be 13-15 volts.
  8.  

IDLE UP SOLENOID



Testing

The idle up solenoid valve can only be checked using the Hyundai FBC tester.

  1. Connect FBC tester to the ECU harness connector at terminal No. 2 .
  2.  
  3. Set the select switch to the A mode and check switch to 7 .
  4.  
  5. With the engine at idle and electrical accessories turned ON , the meter should read 0-0.6 volts.
  6.  
  7. With the engine running at 2000 rpm and the electrical accessories ON , the reading should be 9-15 volts.
  8.  

CHOKE HEATER



Testing

See Figure 6

  1. Disconnect the electric choke heater connector and check the resistance of the heater.
  2.  



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Fig. Fig. 6: Choke heater testing

  1. The resistance should be approx. 6 ohms at 68°deg;F.
  2.  
  3. If the resistance is a great deal out of range or the circuit is open, replace the choke mechanism.
  4.  

 
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