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Home >> Honda >> 1989 >> Prelude S, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Tests W/Codes - CARBURETED >> Trouble Code Tests >> Code 3 - Map Sensor

Code 3 - Map Sensor

  1. Turn ignition off. Remove "EFI/ECU" fuse in under-hood relay panel for 10 seconds to reset ECU. Start and warm engine to normal operating temperature. Verify if "CHECK ENGINE" light is on and if LED is flashing Code 3. If not, problem is intermittent. Test drive and check "CHECK ENGINE" light again.
  2. If light is on, turn ignition off. Connect 3-wire test harness connector between MAP sensor and sensor harness. Turn ignition on. Measure voltage between Red (pos.) and Green (neg.) terminals. If reading is about 5 volts, go to step 3). If not, measure voltage between Red (pos.) terminal and ground.
  3. If measured voltage is approximately 5 volts, repair open in Yellow/White wire between ECU terminal A7 and MAP sensor. If voltage is not 5 volts, substitute a known good ECU. If condition is rectified, replace original ECU.
  4. Measure voltage between White (pos.) and Green (neg.) terminals. If reading is not about 3 volts, replace MAP sensor or repair open or short in White/Blue wire between ECU terminal A6 and MAP sensor.
  5. If measured voltage is about 3 volts, turn ignition off. Connect ECU test harness connector "A" between ECU connectors. See Figure . Turn ignition on. Measure voltage between terminals A6 (pos.) and A16 (neg.). If 3 volts is not present, repair open in White/Blue wire between ECU terminal A6 and MAP sensor. If not go to step 6).
  6. If 3 volts was present, substitute a good known ECU and retest. If condition is rectified, replace original ECU.
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