Code P2251 Hyundai Elantra

Code P2251 Hyundai ElantraI have Engine code p2251 on my 2004 Hyundai Elantra, what could be the cause? I also have codes po507 po301


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.

Possible causes
– Faulty Heated Oxygen Sensor Bank 1 Sensor 1
– Heated Oxygen Sensor Bank 1 Sensor 1 harness is open or shorted
– Heated Oxygen Sensor Bank 1 Sensor 1 circuit poor electrical connection
P2251 Hyundai Description


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.

Possible causes
– Dirty throttle body
– Electric throttle control actuator mis-adjusted or damaged
– Faulty Electric throttle control actuator
– Intake air leak
– Poor electrical connection to the Intake Air Control (IAC) valve

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.

Possible causes
– Faulty spark plug 1
– Clogged or faulty fuel injector 1
– Faulty ignition coil 1
– Fuel injector 1 harness is open or shorted
– Fuel injector 1 circuit poor electrical connection
– Ignition coil 1 harness is open or shorted
– Ignition coil 1 circuit poor electrical connection
– Insufficient cylinder 1 compression
– Incorrect fuel pressure
– Intake air leak