Vehicle application:
2004-’06 Hyundai Elantra GLS 2.0L and 2004 Hyundai Elantra GT 2.0L

The check engine light is on with a post catalyst fuel system lean code P2096, an oxygen (O2) sensor stuck lean B1/S2 code P2270, and an O2 sensor no activity B1/S2 code P0140.

Potential Causes:
Air fuel ratio (AFR) sensor, exhaust flex pipe, fuel pump, heated oxygen sensor (HO2S), mass air flow (MAF) sensor

Tests/Procedures:     
1. Monitor the front air/fuel ratio sensor for about 2 volts at idle, voltage should go down a little (rich) under heavy acceleration and up a little (lean) on deceleration. Voltage should increase to about 3.2 volts in fuel cut. (Hard deceleration from 4,000 rpm).

2. Monitor the rear oxygen sensor to be about 0.4 to 0.6 volts and steady, voltage should go up (rich) under heavy acceleration and down (lean) on deceleration.

3. Check the fuel trims to be close to 0%, add fuel and create a vacuum leak to see if the air/fuel ratio sensor reacts and the fuel trim changes.

4. Check the mass air flow sensor voltage at the pink wire to be about 1.4 volts at idle and about 2.5 volts at 3,000 rpm.

5. Have a helper partially plug the tail pipe while you check for exhaust leaks.

6. Check fuel pressure to be about 49.8 psi.

Courtesy of Identifix, Inc.