Code 1 &/Or Code 2 - O2 Sensor (2.0)

NOTE: 2.0L is equipped with 2 O2 sensors. Code 1 indicates problem with O2 sensor "A" and Code 2 indicates problem with O2 sensor "B".

Turn ignition off. Remove CLOCK fuse in underhood fuse/relay block for 10 seconds to reset ECU. Inspect fuel pressure regulator. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE Section. Repair or replace as necessary. Warm engine to normal operating temperature (cooling fan comes on).
Hold engine speed at 1500 RPM for 15 minutes. DO NOT close throttle completely. If CHECK ENGINE light comes on and LED indicates Code 1 or 2, go to step 3). If LED does not indicate Code 1 or 2, failure is intermittent. Check for loose wires and connections at ground (right shock tower), O2 sensor and ECU.
Disconnect O2 sensor connector. Connect voltmeter between O2 sensor connector and ground. Warm engine to normal engine temperature again. While watching voltmeter, open throttle wide open and then close throttle. If voltage is greater than .6 volt at wide open throttle and below .4 volt when throttle is quickly released, go to next step. If voltage is not as specified, replace O2 sensor.
Turn ignition and engine off. Connect PGM-FI Test Harness between ECU and connector. Connect voltmeter between ECU harness terminals A18 (+) and C16 (-) for O2 sensor "A". Connect voltmeter between ECU harness terminals A18 (+) and B11 (-) for O2 sensor "B". Restart and warm engine to normal operating temperature. While reading voltmeter, open throttle wide open then quickly close throttle.
If voltage is greater than .6 volt at wide open throttle and below .4 volt when throttle is quickly released, substitute a known good ECU, and recheck. If symptoms go away, replace original ECU. If voltage is not as specified, repair open or short in O2 sensor wire (White wire for O2 sensor "A" and Red/Blue wire for O2 sensor "B").