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P2251 is a diagnostic trouble code (DTC) for "O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1
P2251 is an OBD-II generic code. The engine control module (ECM) monitors the negative current control of the O2 sensor heater circuit. If the current cannot be controlled and the voltage does not change on the return wire, then the ECM detects this as an open circuit in the heater circuit for the O2 sensor heater circuit.
Scans codes and documents the code in the ECM and looks at the freeze frame data for failure.
Measures the voltage to the O2 sensor on the heater circuit.
Measures the resistance of the O2 sensor heater circuit at the ECM and at the sensor and checks to see if it is at the correct specifications.
Checks the harness for short or broken wires.
Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so the failure may be duplicated and repaired
Failing to clear the ECM codes after the codes are fixed
Replacing an O2 sensor without verifying the failure of the heater circuit. This could be an intermittently shorted wire in the harness
Code P2251 is major failure in the O2 sensor heater circuit and the O2 sensor may be rendered unable to respond to the exhaust O2 and cause the ECM to go into failure mode. This may cause the vehicle to fail emission testing and cause drive complaints depending on the manufacturer.
Replacing the O2 sensor for bank 1 sensor 1
Repairing an open or short in the sensor wiring or connector
Replacing the ECM for an open in the O2 heater circuit
Code P2251 is for the O2 sensor heater circuit. This heater allows the O2 sensor to respond quicker than an O2 sensor that does not have one. This circuit is on most (if not all) model cars and light trucks since about 1990 and later.
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