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Code 3, Map Sensor

  1. Turn ignition off. Disconnect alternator sense fuse in under-hood relay box for 10 seconds to reset ECU. Start engine and observe PGM-FI warning light. If light is off, problem is intermittent. Test drive and check again.
  2. If light is on, turn ignition off. Connect inspection adaptor 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 4). If not, measure voltage between Red (pos.) terminal and ground. If voltage is still not 5 volts, go to step 3). If voltage is about 5 volts, repair open in Green/White wire between ECU and MAP sensor.
  3. Turn ignition off. Connect system checker harness between ECU and ECU harness. Measure voltage between terminal C15 (pos.) and C16 (neg.) with ignition on. If voltage reading is about 5 volts, repair open Yellow/White wire between ECU and MAP sensor. If voltage is not about 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 short in White wire between ECU and MAP sensor.
  5. If measured voltage is about 3 volts, turn ignition off. Connect system checker harness between ECU and ECU connectors. Turn ignition on. Measure voltage between terminal C11 (pos.) and C16 (neg.). If there is not about 3 volts present, repair open White wire between ECU and MAP sensor.
  6. If there is about 3 volts present, substitute a known good ECU. If condition is rectified, replace original ECU.
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