LEMON Manuals: Even more car manuals for everyone
Home >> Nissan-Datsun >> 1984 >> Maxima 4D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> EFI CEC System/Tests >> System Testing & Diagnosis

System Testing & Diagnosis

  1. Test throttle valve switch. Connect ohmmeter positive lead to terminal 29 of EFI control unit 35-pin connector and negative lead to terminal 30. See Fig 1 . With throttle released, there should be continuity. With throttle depressed, there should be no continuity. If okay, go to next step. If no good, adjust throttle valve switch as described in ADJUSTMENTS.
    Fig 1: Maxima EFI Control Unit 35-Pin Connector
    G42358
  2. Connect ohmmeter negative lead to body ground and check continuity at terminals 29 and 30 of 35-pin connector. Resistance should be infinity in both cases. If okay, go to next step. If no good, check resistance at throttle valve switch harness connector terminals 29, 30 and engine. See Fig 2 . Resistance should be infinite. If okay, check harness. If no good, replace throttle valve switch.
  3. Connect ohmmeter positive lead to terminal 33 of 35-pin connector and negative lead to terminal 34. Resistance should be 100-400 ohms. If okay, go to next step. If no good, check resistance between terminals 33 and 34 of harness connector for air flow meter. Resistance should be 100-400 ohms. If okay, check harness. If no good, replace air flow meter.
    Fig 2: Checking Throttle Valve Harness Connector
    G42359
    Fig 3: Air Flow Meter Terminal Locations
    G42360
  4. Connect ohmmeter positive lead to terminal 34 of 5-pin connector and negative lead to terminal 35. Resistance should be 200-500 ohms. If okay, check harness. If no good, replace air flow meter.
  5. Connect ohmmeter positive lead to terminal 32 of 35-pin connector and negative lead to terminal 34. Readings other than zero or infinity are acceptable. If okay, go to next step. If no good, measure resistance at terminals 32 and 34 of air flow meter harness connector while sliding flap. Readings other than zero or infinity are acceptable. If okay, check harness. If no good, replace air flow meter.
  6. Connect ohmmeter negative lead to body ground and check continuity at terminals 32, 33, 34 and 35 of 35-pin connector. Resistance should be infinity. If okay, go to next step. If no good, check resistance at air flow meter body and any one of terminals 32, 33, 34 and 35. If there is no continuity, check harness. If continuity exists, replace air flow meter.
  7. Test air flow meter flap. Fully open flap by hand to check that it opens smoothly without binding. If it does, replace air flow meter. If not, go to next step.
  8. Check air temperature sensor. Connect ohmmeter positive lead to terminal 25 of 35-pin connector and negative lead to terminal 34. Resistance should be below 2900 ohms at temperatures of 68°F (20°C) or above, and 2100 ohms or above at temperatures below 68°F (20°C).
  9. If okay, go to next step. If no good, resistance at terminals 25 and 34 of air flow meter harness connector. Resistances should be as listed in step 8). If okay, check harness. If no good, replace air flow meter.
  10. Connect ohmmeter positive lead to terminal 25 of 35-pin connector and negative lead to body ground. Resistance should be infinity. If okay, go to next step. If no good, measure resistance at terminal 25 and air flow meter body. Resistance should be infinity. If okay, check harness. If no good, replace air flow meter.
  11. Connect ohmmeter positive lead to terminal 14 of EFI control unit 35-pin connector and negative lead to body ground. Resistance should be below 2900 ohms at temperatures of 68°F (20°C) or above, and 2100 ohms or above at temperatures below 68°F (20°). If okay, test is complete. If no good, go to next step.
  12. Dip the water temperature sensor into water maintained at a temperature of 68°F (20°C) and measure resistance. Resistance should be 2100-2900 ohms. At 122°F (50°C), resistance should be 680-1000 ohms. If okay, repair or replace harness. If not okay, replace water temperature sensor.
  13. Check exhaust gas sensor. Connect ohmmeter positive lead to terminal 31 of 35-pin connector and negative lead to body ground. Resistance should be zero ohms. If okay, go to next step. If no good, check mixture ratio feedback system.
  14. Check thermotime switch. Connect ohmmeter positive lead to terminal 4 of 35-pin connector and negative lead to body ground. Resistances should be as listed in table.
    THERMOTIME SWITCH RESISTANCES

    Water Temperature Ohms
    77°F (25°C) or Above Infinity
    57-77°F (14-25°C) Zero or Infinity
    Below 57° (14°C) Zero
  15. If okay, go to next step. If no good, measure the resistance between terminal 46 and switch body. See Fig 4 . Resistances should be as listed in table. Measure the resistance between terminal 45 and switch body. Ohmmeter reading should be 40-70 ohms. If okay, check harness. If no good, replace switch.
    Fig 4: Thermotime Switch Terminal Numbers
    G42361
  16. Connect ohmmeter negative lead to body ground and check continuity at terminals 15, 19, 20 and 22. There should be continuity. If okay, ground circuits are okay. If no good, check wiring harness.
  17. Check air regulator. Connect ohmmeter positive lead to terminal 21 of control unit and negative lead to body ground. Resistance should be 25-90 ohms. If no good, check air regulator fuel pump. If okay, connect EFI harness connector to control unit. Turn ignition ON. Listen for fuel pump operating sound for a few seconds. If no sound is heard, check fuel pump relay. If fuel pump operates, check air regulator.
  18. Start engine, and pinch rubber hose between throttle chamber and air regulator. If engine speed decreases during warm-up or remains unchanged, air regulator is okay. Disconnect hoses from both ends of air regulator, and visually check to see if air regulator shutter opens.
  19. Disconnect electric connector of air regulator and check continuity. If there is no continuity, air regulator is faulty. Pry air regulator shutter open with a flat-blade screwdriver and then close. If it opens and closes smoothly, it is operating properly. IF air regulator does not test out okay, replace.
  20. Check cold-start valve. Connect voltmeter positive lead to terminal 4 of 35-pin connector and negative lead to body ground. Battery voltage should be present. If okay, cold-start valve is okay. If not, disconnect battery ground. Remove 2 screws attaching cold-start valve to intake manifold and remove valve.
  21. Put valve in a transparent glass container and plug opening with a clean rag. Using 2 wires, connect each terminal to cold start connector. Connect other terminals of jumper wires to battery voltage. If fuel is injected, valve is okay. Check harness. If not, replace valve.
  22. Check ignition coil trigger input. Connect voltmeter positive lead to terminal 18 of 35-pin connector and negative lead to body ground. Connect starter motor "S" terminal and battery ground cable. Turn ignition to "START" position. Pointer should deflect. If okay, trigger input is okay. If no good, check ignition coil and harness.
  23. Check injector circuit. Connect voltmeter positive lead to each of the listed terminals of 35-pin connector and negative lead to body ground. Connect battery ground cable. Voltmeter should read battery voltage. If okay, go to next step. If no good, disconnect battery ground. Disconnect electrical connectors from injectors. Check continuity between terminals. If there is no continuity, injectors are faulty.
    INJECTOR TESTING

    Terminal Number Injector Number
    8 1
    5 2
    7 3
    6 4
    3 5
    2 6
  24. Check EFI relay. Connect ohmmeter positive lead to terminal 27 of EFI control unit 35-pin connector and negative lead to body ground. Connect battery ground cable. With ignition on, there should be battery voltage. If okay, go to next step. If not, check relay as listed in table. See Fig 5 .
  25. Connect EFI harness connector to ECU. Turn ignition switch to "IGN". Listen for fuel pump operating sound for a few seconds. If there is no sound, connect ohmmeter positive lead to terminal 13 of EFI control unit 35-pin connector and negative lead to body ground. Ohmmeter should read anything but zero infinity.
    Fig 5: Relay Locations on Relay Bracket
    G42362
  26. If no good, check relay as listed in table. If okay, check fuel pump and circuit. If fuel pump is okay, check relay as listed in table.
    EFI RELAY CONTINUITY

    Terminal Nos. With 12 Volts DC Between 1 & 2 With NoVoltage Applied
    1-2 N/A Continuity
    3-5 Continuity No Continuity
    3-6 No Continuity Continuity
  27. Check ignition start signal. Connect voltmeter positive lead to terminal 26 of EFI control unit 35-pin connector and negative lead to body ground. Disconnect starter "S" terminal. Connect battery ground cable. With ignition in "START" position, there should be battery voltage. If okay, ignition start signal is okay. If not, check ignition coil and harness.
Fig 6: Maxima EFI Control System Wiring Diagram
G42369
scientia non olet · About LEMON Manuals