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Federal Models

  1. Position the ECC control unit so that Red and Green inspection lamps can be easily looked at. Start engine and warm up to operating temperature. Verify that diagnosis start switch is in "OFF" position (farthest position away from inspection lamps).
  2. Run engine at 2000 RPM for about 5 minutes under no-load. Keep engine speed at 2000 RPM and check that Green lamp goes on and off more than 5 times in 10 seconds. If no good, go to next step. If okay, go to step 5).
  3. If no good, turn off engine and disconnect battery ground cable. Disconnect 20-pin connector from control unit. Disconnect exhaust gas sensor harness connector and connect terminal for exhaust gas sensor harness connector to ground with a jumper wire.
  4. Check for continuity between terminal 2 for 20-pin connector and ground metal on vehicle body. See Figure . If continuity exists, replace exhaust gas sensor. If it does not exist, repair or replace ECC harness. Return to step 1).
  5. Turn off engine and turn the diagnosis start switch on ECC control unit to the "ON" position (closest position to inspection lamps). Turn ignition on and check Red and Green lamps on ECC control unit for lighting interval without starting engine. See Figure .
  6. If case displayed is case 1, go to step 13). If case 2 is displayed or if Red lamp is off and Green lamp is on, check each sensor. Turn ignition off. Verify that each harness connector is connected securely.
  7. If not, correct and return to step 5). Disconnect ECC 20-pin connector from control unit. Connect terminals between ECC control unit and harness connector of terminals 19 and 20 with wire.
  8. Disconnect vacuum hose for vacuum sensor and connect vacuum pump to vacuum sensor. Turn ignition on and measure resistance or voltage of each sensor.
  9. For water temperature sensor, measure across 8 and 19. For air temperature sensor, check between 1 and 19. For both, resistance should be below 2900 ohms at 68°F (20°C) or above, and 2100 or above at temperatures below 68°F (20°C).
  10. Measure voltage at terminals 9 and 19 for vacuum sensor. Voltage should be 4.0 volts with no vacuum applied, and .5 volts with 26 in. Hg vacuum applied. If sensors test out okay, replace control unit and return to step 5). If no good, go to next step.
  11. Disconnect each sensor harness connector. Connect vacuum terminals to battery voltage with jumper wires and check output voltage. Voltage should be 4.0 volts with no vacuum applied, and .5 volts with 26 in. Hg vacuum applied. If no good, replace vacuum sensor and return to step 5). See Fig 1 -Fig 4 . If okay, go to next step.
    Fig 1: Connecting Terminals Between ECC Ctrl Unit Harness Connector of Terminals No. 19 and 20
    G50A01721
    Fig 2: Connecting Vacuum Pump to Vacuum Sensor
    G50C01722
    Fig 3: Output Voltage Check
    G50E01723
    Fig 4: Connecting Vacuum Sensor Terminals to Battery (+) and (-) Terminals
    G50D07593
  12. Measure the resistance of water temperature sensor and intake air temperature sensor at terminals. For both, resistance should be below 2900 ohms at 68°F (20°C) or above, and 2100 or above at temperatures below 68°F (20°C). If no good, replace malfunctioning sensor. If okay, repair or replace ECC harness. Reconnect sensor harness connectors and return to step 5).
  13. If case 1 was displayed in step 6), check each solenoid and relay. Make sure that each harness connector is securely connected. If not, correct and return to step 5). Disconnect each harness connector. Measure resistance of each solenoid and relay.
    SOLENOID RESISTANCES SPECIFICATIONS

    Application Ohms
    Mixture Heater 60-85
    Air-Fuel Ratio 30-50
    Richer Solenoid 20-40
    Anti-Dieseling Solenoid 25-45
    Air Injection 25-45
    Idle Speed Control Solenoid 25-45
  14. If idle speed control solenoid resistance is out of specifications, replace vacuum control modulator. If resistance of any other solenoid or relay is incorrect, replace and return to step 5). If okay, go to next step.
  15. Reconnect harness connectors. Disconnect ECC 10-pin connector and 20-pin connector from control unit. Turn ignition on. Measure the voltage between each listed terminal and ground. Voltage should be 12-14 volts. If not, replace or repair harness. If okay, replace ECC control unit.
SOLENOID & RELAY CHECK

Application Check Terminal
Mixture Heater Relay 3
Air-Fuel Ratio Solenoid F
Richer Solenoid B
Anti-Dieseling Solenoid G
Air Injection Solenoid H
Idle Speed Control Solenoid I
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