Code P2251 Hyundai Elantra

I have Engine code p2251 on my 2004 Hyundai Elantra, what could be the cause? I also have codes po507 po301

RESPONSE

Engine Code P2251 HYUNDAI – O2 Sensor Reference Ground Circuit/Open Bank 1 Sensor 1

The linear O2 sensor is mounted on the front side of the Catalytic Converter (warm-up catalytic converter) or in the front exhaust pipe. It detects a wide range of air/fuel ratios in the exhaust gas from the rich to lean regions. This linear O2 sensor produces a current that corresponds to a specific air/fuel ratio. The Powertrain Control Module (PCM) monitors this signal and determines whether the air/fuel mixture is rich or lean. The PCM constantly monitors the linear O2 sensor and increases or decreases the fuel injection duration using this signal. This is called closed-loop fuel control operation.

Code P0507 – Idle Control System RPM Higher Than Expected
If there are no intake leaks, clean throttle body, adjust engine idle and erase engine code. If the code comes back you may have to replaced the Electric Throttle Control Actuator (Motor) to repair the problem.

Code P0301 – Cylinder 1 Misfire Detected

The P0301 code means that the cylinder 1 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 1. If the problem persist more tests needs to be done to diagnose problem.