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System Testing

  1. Disconnect the battery ground cable. Disconnect ECC 10-pin and 20-pin harness connectors from control unit.
  2. Connect ohmmeter positive lead to terminal No. 4 and negative lead to body ground. With transmission in Neutral or Park, there should be zero ohms. In any other position, resistance should be infinity. If okay, neutral/park switch circuit is okay.
  3. Shift lever to any position except Neutral. Connect ohmmeter positive lead to terminal No. 4 and negative lead to body ground. With clutch depressed, there should be zero ohms. With clutch released, resistance should be infinity. If okay, clutch switch circuit is okay.
  4. Connect ohmmeter positive lead to terminal No. 6 and negative lead to body ground. With throttle depressed, there should be zero ohms. With throttle released, resistance should be infinity. If okay, throttle valve switch circuit is okay. If not, adjust the throttle valve switch.
  5. For California models with automatic transmission, and for Federal models with automatic, manual and 4WD transmission (Except Cab and Chassis), perform the following procedure:
  6. Disconnect vacuum hose from vacuum switch for full throttle and connect vacuum pump. Connect ohmmeter positive lead to terminal No. 7 and negative lead to body ground. With a vacuum of below 4.72 in. Hg applied, resistance should be zero. With vacuum of above 4.72 in. Hg applied, resistance should be infinity.
  7. Connect the ohmmeter positive lead to terminal No. 10 and negative lead to body ground. With a vacuum of below 5.91 in. Hg applied, resistance should be zero. With a vacuum reading of above 5.91 in. Hg applied, resistance should be infinity. If okay, vacuum switch circuit is okay.
  8. For California models with manual transmission and 4WD, and for Federal models with manual transmission (Cab and Chassis), disconnect vacuum hose from vacuum switch for full throttle and connect vacuum pump. Connect ohmmeter positive lead to terminal No. 7 and negative lead to body ground.
  9. With a vacuum of below 3.14 in. Hg applied, resistance should be zero. With vacuum of above 3.15 in. Hg applied, resistance should be infinity. Connect ohmmeter positive lead to terminal No. 10 and negative lead to body ground. With vacuum of below 5.91 in. Hg applied, resistance should be zero. With a vacuum of above 5.91 in. Hg applied, resistance should be infinity. If resistance is okay, vacuum switch circuit is okay.
  10. Connect ohmmeter positive lead to terminal 8 and negative lead to terminal 16. With water temperature above 68°F (20°C), resistance should be below 2900 ohms. With water temperature below 68°F (20°C), resistance should be 2100 ohms or above. If okay, water temperature sensor and circuit is okay. If not, go to next step.
  11. Dip the water temperature sensor into water maintained at a temperature of 68°F (20°C). Resistance should be 2100-2900 ohms. At 122°F (50°C), resistance should be 680-1000 ohms. If okay, repair or replace ECC harness. If not okay, replace water temperature sensor.
  12. Disconnect exhaust gas sensor harness connector. Connect terminal for exhaust gas sensor to ground with a jumper wire. Connect ohmmeter positive lead to terminal No. 2 and negative lead to body ground. Resistance should be zero ohms. If okay, exhaust gas sensor circuit is okay.
  13. Disconnect altitude switch harness connector. Connect jumper wire between 2 terminals of harness connector. Connect battery ground cable and turn ignition switch to the "ON" position. Connect positive lead of ohmmeter to terminal No. 17, and negative lead to ground. With jumper wire in place, resistance should be zero. With jumper disconnected, resistance should be infinite. If test is okay, altitude switch circuit is okay.
  14. Connect ohmmeter negative lead to body ground and positive lead first to terminal A and then terminal E. Resistance should be zero. If okay, ground circuits are okay. If not, check harness.
  15. On vehicles with Z24 engine, disconnect vacuum hose from vacuum switch for spark plug switching control, and connect a vacuum pump. For Z24 manual transmission Federal models (except for Cab and Chassis models), connect positive lead of ohmmeter to terminal B and negative lead to ground. With 3.15 in. Hg of vacuum applied, or less, resistance should be zero. Applying more than 3.15 in. Hg of vacuum should yield a resistance of infinity. If test is not okay, check harness, ignition control unit and vacuum switch.
  16. On vehicles other than the ones mentioned in step 13), turn ignition switch to the "ON" position. Connect positive lead of ohmmeter to terminal B, and negative lead to ground. Pointer should deflect. If so, spark plug switching control system is okay. If not, check harness, ignition control unit and vacuum switch.
  17. Connect voltmeter positive lead to terminal C and negative lead to body ground. Disconnect alternator L terminal. With ignition switch in the "ON" position, battery voltage should be present. If okay, mixture heater circuit is okay. If not, check wire harness, auto choke relay and mixture heater relay.
  18. Connect voltmeter positive lead to terminal D and negative lead to body ground. With ignition switch in the "START" position, meter pointer should deflect. If okay, trigger input to the control unit is okay. If not, check ignition coil and wire harness.
  19. Connect voltmeter positive lead to terminal F and negative lead to body ground. With ignition switch in the "ON" position, battery voltage should be present. If okay, air fuel-ratio control solenoid circuit is okay.
  20. Connect voltmeter positive lead to terminal G and negative lead to body ground. With ignition switch in the "ON" position, battery voltage should be present. If okay, anti-dieseling solenoid circuit is okay.
  21. Connect voltmeter positive lead to terminal H and negative lead to body ground. With ignition switch in the "ON" position, battery voltage should be present. If okay, battery source circuit is okay.
  22. Connect voltmeter positive lead to terminal I and negative lead to body ground. With ignition and A/C switches in the "ON" position, battery voltage should be present. If okay, FICD circuit is okay.
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