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Ecu & Wiring

  1. Remove electrical plug from ECU (behind dash on right side). Test involves checking for voltage or continuity at different pins on ECU wiring plug. Pins are numbered for test procedure. See Figure .
  2. ECU receives battery voltage through oxygen sensor system relay. With ignition ON, check pin No. 8 for 12 volts with voltmeter. ECU should receive 12 volts at pin No. 21 from canister purge solenoid with ignition ON or OFF. Using ohmmeter, measure between pin No. 5 and ground for continuity. Correct meter reading is 0 ohms.
  3. To check kickback idle switch, turn ignition ON and connect ohmmeter between pin No. 3 and ground. Meter reading should be 0 ohms (continuity) with accelerator pedal depressed. Meter should read infinity (open circuit) with accelerator pedal released.
  4. To check that battery voltage is supplied through manifold heater relay to ECU, connect voltmeter to pin No. 13. Reading should be 12 volts. To check shielding of oxygen sensor wiring, disconnect lead to oxygen sensor. Connect ohmmeter between pin No. 1 and pin No. 14. Meter should read infinity (open circuit).
  5. To check wire from ECU to oxygen sensor, ground wire that was disconnected from oxygen sensor. Ohmmeter connected between pin No. 14 and ground should read 0 ohms (continuity). To check ground circuit, connect ohmmeter between pin No. 11 and ground. Reading should be 0 ohms (continuity).
  6. To check frequency valve circuit, connect voltmeter to pin No. 18 and ground. With ignition ON, meter reading should be 12 volts. To check frequency valve, connect ohmmeter between pin No. 18 and ground with ignition OFF. Meter reading should be 18-26 ohms.
  7. To check temperature sensor, connect ohmmeter between pin No. 24 and ground. Readings should be: 8000-1500 ohms at 32-59°F (0-15°C); 4000-700 ohms at 59-104°F (15-40°C); 2000-100 ohms above 104°F (40°C).
  8. Check coil feed for engine RPM signal (tach signal). With ignition ON, connect voltmeter to pin No. 19 and ground. Meter reading should be 12 volts after 2 seconds. To check duty cycle lead, connect ohmmeter between pin No. 17 and ground. Meter reading should be infinity (open circuit).
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