P2251 OBD-II Trouble Code: O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P2251 code

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 for $114.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.0 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford $114.99 $20.0
Toyota $114.99 $20.0
BMW $124.99 $20.0
SCHEDULE P2251 DIAGNOSTIC Get a fair and transparent estimate upfront

P2251 code definition

O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1

What the P2251 code means

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.

What causes the P2251 code?

  • The O2 sensor for bank 1 sensor 1 has an open circuit in the heater circuit.
  • A broken wire or connector for the O2 sensor
  • An open wire on the power supply circuit from the ECM to the O2 sensor heater circuit
  • An open or short on the return signal wire back to the ECM

What are the symptoms of the P2251 code?

  • The Check Engine Light will be illuminated and the code is set in ECM memory as a fault.
  • The ECM may lose control of the fuel control circuit for the O2 sensor for bank 1 sensor 1.
  • The ECM may go into failure management mode to control the fuel to the engine.
  • The engine fuel mileage will go down and the engine may have various fuel-related symptoms.

How does a mechanic diagnose the P2251 code?

  • 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.

Common mistakes when diagnosing the P2251 code?

  • 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

How serious is the P2251 code?

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.

What repairs can fix the P2251 code?

Additional comments for consideration regarding the P2251 code

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.

Need help with a P2251 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

Check Engine Light
trouble codes
P2251

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P2251 code.

SCHEDULE P2251 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(7400)

Rating Summary
6879
249
58
41
173
6879
249
58
41
173
 at YourMechanic

David

13 years of experience
393 reviews
David
13 years of experience
Chevrolet Malibu L4-2.4L - Check Engine Light is on Inspection - Marietta, Georgia
He explained everything to me in detail on what I needed to know about my car. Definitely recommend him for getting the job done.
 at YourMechanic

Raymond

37 years of experience
402 reviews
Raymond
37 years of experience
Toyota Camry L4-2.2L - Check Engine Light is on - Las Vegas, Nevada
Raymond did a great job however I was charged for two hours labor and he was only here less than 45 minutes. should I expect this on future appointments with your mechanic ?
 at YourMechanic

Shane

17 years of experience
217 reviews
Shane
17 years of experience
Volkswagen EuroVan V6-2.8L - Check Engine Light is on Inspection - Austin, Texas
Arrived on time. Explained the issues he found and how he will fix it. I have parts on order and will schedule an appointment to have Shane install the parts when they arrive.
 at YourMechanic

Kanstantsin

19 years of experience
51 reviews
Kanstantsin
19 years of experience
Ford F-150 V8-4.6L - Check Engine Light is on Inspection - Littleton, Colorado
Kanstantsin arrived early. Was very courteous and professional. Will highly recommend to anyone. Thank you Kanstantsin.


More related articles

P2141 OBD-II Trouble Code: Exhaust Gas Recirculation Throttle Control Circuit Low
P2141 P2141 code definition Exhaust Gas Recirculation Throttle Control Circuit Low What the P2141 code means P2141 is an OBD-II generic code for the engine control module (ECM) detecting the exhaust gas recirculation (EGR) control valve circuit is low. This...
P0571 OBD-II Trouble Code: Cruise Control/Brake Switch A Circuit Malfunction
P0571 means there is a problem with the switch that that deactivates the cruise control system which causes the cruise control to not function.
P0582 OBD-II Trouble Code: Cruise Control Vacuum Control Circuit/Open
P0582 P0582 OBD-II Trouble Code: Cruise Control Vacuum Control Circuit/Open P0582 code definition The P0582 code indicates that there has been a malfunction detected in the cruise control vacuum control circuit by the car’s computer. What the P0582 code means...

Related questions

Engine problems.
Hello. From what you describe it would appear likely that the backfiring and performance issues are a result of the fuel problem. A rich fuel mixture can be caused by a wide variety of issues. A few things I would...
Fuel pump
This may happen when the fuel pump is working intermittently or not maintaining the proper fuel pressure. This may also be related partially to the fuel pressure regulator (https://www.yourmechanic.com/services/fuel-pressure-regulator-replacement) which helps to maintain the proper fuel pressure throughout the system....
2008 Buick Enclave engine light on with code p1682 and car stays running with key off for while then dies, ECM is humming,
Code P1682 sets if the ECM detects a difference in the voltage levels of the two main power inputs to the ECM. Basically, the code will be stored when one voltage input has a significantly different value than the other...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com