Code 1, Code 2: Oxygen Sensor

NOTE: For wiring diagrams, see WIRING DIAGRAMS article. For vacuum diagrams, see VACUUM DIAGRAMS article.

Turn ignition off. Remove alternator sense fuse in under-hood relay box (for 10 seconds to reset ECU. Start and warm engine to normal operating temperature. Check fuel pressure. See BASIC TESTING article. Repair fuel system if not within specification. If fuel pressure is within specification, proceed to next step.
Road test vehicle. With transmission in second gear, accelerate at wide open throttle for at least 5 seconds. Then decelerate with throttle fully closed for at least 5 seconds. Check if CHECK ENGINE light is on and if LED is indicating Code 1 or Code 2. If light is not on, problem is intermittent.
Check for poor connections at oxygen sensor, ECU and round connector No. C216 at right shock tower.
NOTE: per acura service news number ASN 0390-03 oxygen sensor connector should not be disconnected at this point. backprobe the connector to obtain voltages during this test.

Attach voltmeter to vehicle ground and oxygen sensor connector.
With engine at normal operating temperature, momentarily open throttle wide open, then close throttle. Voltage at wide open throttle should be greater than .6 volt and less than .4 volt at full closed throttle. On Integra, if voltage is not within specification, replace oxygen sensor.
If voltage is within specification, perform diagnostic procedure for Code 43. On rear oxygen sensor, repair open between ECU terminal C10 (Red/Blue wire) and oxygen sensor.
If voltage is within specification, substitute a known good ECU and recheck. If system operates properly, replace original ECU.