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

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P2251 DIAGNOSTIC 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. 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.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
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.

trouble codes
P2251
Check Engine Light

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P2251 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

4,869

Rating Summary
4,482
187
48
28
124
4,482
187
48
28
124

Peter

41 years of experience
1251 reviews
Peter
41 years of experience
Chevrolet Cruze - Check Engine Light is on Inspection - Phoenix, Arizona
I requested Your Mechanic’s services due to my check engine light coming on. Peter showed up early and was able to diagnose and fix the issue in a timely manner. Peter was also very pleasant and I was charged a fair price for the repair. I’ve also had Peter fix my car on two previous occasions and I was very pleased with his services those times as well. I would definitely recommend him to fix your car as well!

Arturo

25 years of experience
64 reviews
Arturo
25 years of experience
Toyota Matrix - Check Engine Light is on - San Diego, California
Absolutely Excellent. He can answer any inquiries I had and very knowledgeable. Also very helpful and genuine. In addition he gave good recommendations on my car care. I am very glad I found "your mechanic".

Albert

13 years of experience
23 reviews
Albert
13 years of experience
Ford Fusion - Check Engine Light is on - Riverside, California
Albert showed up early, was very professional and informative, would definitely recommend to family and friends

William

15 years of experience
9 reviews
William
15 years of experience
Ford Crown Victoria - Check Engine Light is on - Denver, Colorado
William was such a great help on helping me not only diagnose my vehicle but also helped me better understand my own Car! Such a great experience for my first time using Your Mechanic

More related articles

P0192 OBD-II Trouble Code: Fuel Rail Pressure Sensor Circuit Low Input
P0192 trouble code definition Fuel rail pressure sensor circuit low input What the P0192 code means The power control module (PCM) has...
P0697 OBD-II Trouble Code: Sensor Reference Voltage “C” Circuit/Open
P0697 means there is a fault with the sensor reference voltage "C" circuit, likely due to damaged or shorted wiring or connectors.
P2234 OBD-II Trouble Code: O2 Sensor Signal Circuit Shorted to Heater Circuit Bank 2 Sensor 1
P2234 P2234 code definition O2 Sensor Signal Circuit Shorted to Heater Circuit Bank 2 Sensor 1 What the P2234 code means Code P2234 is an OBD-II generic code for the Engine Control Module (ECM) detecting the O2 sensor signal wire...

Related questions

Heater will not stay hot

Hello. You are likely facing multiple issues at once. The low coolant would absolutely cause the heater to function intermittently. If you are continuously losing coolant there is likely a leak on the system and it will need to be...

P0014 on scanner

Hi and thanks for contacting YourMechanic. The code p0014 refers to the camshaft position sensor 'B' circuit with the timing over-advanced. The TPS will not make the computer think of a cam not adjusting correctly. With the code p0014, check...

Engine stumbles around 3000 RPM.

Hi there. The engine could be stumbling for the coil pack or distributor may not be functioning correctly. As the coil pack or distributor gets old, the parts tend to become weak and is not able to send an electrical...

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.

1-800-701-6230 · hi@yourmechanic.com