Code 1: O2 Sensor

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.

Turn ignition off. Remove HAZARD fuse at battery positive terminal for 10 seconds to reset ECU. Start and warm engine to normal operating temperature. Check fuel pressure. See BASIC TESTING article in the ENGINE PERFORMANCE Section. Repair fuel system if not within specification.
Road test vehicle. With transmission in second gear, accelerate at wide open throttle for at least 5 seconds, and 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.
If light is not on, problem is intermittent. Check for poor connections at O2 sensor, ECU and round connector No. C216 at right shock tower.
If light is on, disconnect O2 sensor connector. Attach voltmeter to vehicle ground and O2 sensor connector.
With engine at normal operating temperature, momentarily open throttle wide open, and then close throttle. Voltage at wide open throttle should be greater than .6 volt and less than .4 volt at fully closed throttle.
If voltage is not within specification, replace O2 sensor. If voltage is within specification, perform diagnostic procedure for Code 43.