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Home >> Acura >> 1991 >> Integra LS, 2D Hatchback, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 43: Fuel Supply System
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Code 43: Fuel Supply System

NOTE: For wiring diagrams, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. For vacuum diagrams, see VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section.
  1. Turn ignition off. Remove HAZARD fuse in main fuse box for 10 seconds to reset ECU. Start engine, and allow cooling fan to come on. Hold engine at 3000 RPM for 2 minutes. Observe CHECK ENGINE and LED lights. If lights are not on, problem is intermittent.
  2. Check for poor and loose connections at O2 sensor and round connector C216 at right shock tower. If CHECK ENGINE light is on and LED indicates Code 43, inspect fuel pressure regulator. See BASIC TESTING article in the ENGINE PERFORMANCE Section. If driveability problems are also present, test fuel related components. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE Section. Repair as necessary.
  3. If fuel regulator is okay, disconnect O2 sensor. With engine running, measure voltage between O2 sensor and ground. Voltage should be above .6 volt at wide open throttle up to 4500 RPM. When throttle is quickly released, voltage should be .4 volt.
  4. If voltage is not correct, replace O2 sensor. If voltage is correct, stop engine. Reconnect O2 sensor connector. Connect ECU test harness to ECU. Restart engine, and warm to normal operating temperature. Measure voltage between C16 and A18.
  5. Voltage should be as in step 3). If voltage is not correct, repair open or short in White wire between C16 and O2 sensor. If voltage is correct, substitute a known good ECU, and recheck. If problem goes away, replace ECU.
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