Code 3: Map Sensor

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Turn ignition off. Remove BACK UP fuse at battery positive terminal for 10 seconds to reset ECU. Check ECU for fault codes. See RETRIEVING CODES . If Code 3 is not present, problem is intermittent. Check for poor or loose connections at MAP sensor and ECU connector. Test drive vehicle and retest.
If Code 3 is present, turn ignition off. Disconnect 3-wire MAP sensor connector. Turn ignition on. Measure voltage between MAP sensor Yellow/White (+) wire and body ground. See Fig 1 . If voltage is about 5 volts, go to step 4). If voltage is not about 5 volts, connect "D" connector of ECU Test Harness (07LAJ-PT3010A ) to ECU, leaving vehicle wiring harness disconnected.

Fig 1: MAP Sensor Location & Connector Terminal ID (Vigor)
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn ignition on. Measure voltage between test terminals D19 (+) and D21 (-). If about 5 volts are present, repair open circuit in D19 (Yellow/White wire) between ECU connector and MAP sensor. If about 5 volts are not present, substitute a known good ECU. If problem goes away, replace ECU.
If voltage is about 5 volts in step 2), measure voltage between Yellow/White (+) and Green/White (-) wires at MAP sensor. If about 5 volts are not present, repair open in Green/White wire between ECU terminal D21 and MAP sensor. If voltage is about 5 volts, measure voltage between White/Blue wire (+) and Green/White (-) wire terminal at MAP sensor.
If voltage is about 5 volts, go to step 7). If voltage reading is not about 5 volts, on A/T models, disconnect A/T control unit connector. If about 5 volts are present, replace A/T control unit. If about 5 volts are not present, reconnect A/T control unit connector.
On all models, measure voltage between test harness terminals D17 and D21. If about 5 volts are present, repair open or short in circuit D17 (White/Blue wire) between ECU connector and MAP sensor. If voltage about 5 volts are not present, substitute a known good ECU, and recheck. If about 5 volts are present, replace original ECU.
Turn ignition off. Reconnect 3-wire MAP sensor connector. Connect ECU Test Harness (07LAJ-PT3010A ) between ECU and ECU connector. See Figure . Turn ignition on. Measure voltage between test terminals D17 and D21. If about 3 volts are not present, replace MAP sensor. If about 3 volts are present, substitute a known good ECU. If system functions properly, replace ECU. If about 3 volts are not present, replace MAP sensor.