P0051 Subaru Code - HO2S21 Heater Control Circuit Low
Quick Answer
Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
- What it means
- P0051 Subaru indicates HO2S21 Heater Control Circuit Low.
- Common causes
- Common causes include Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted, Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection.
- Severity
- Moderate - service should be scheduled soon.
- Can I drive?
- The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
Code P0051 Subaru Description
In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.
The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.
What are the Possible Causes of the DTC P0051 Subaru?
- Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1
- Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted
- Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection
- Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 fuse
- Faulty Engine Control Module (ECM)
How to Fix the DTC P0051 Subaru?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0051 Subaru code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about P0051 Subaru Code
1. What are the common symptoms of OBDII code P0051 in a Subaru related to HO2S21 Heater Control Circuit Low?
- Common symptoms include poor fuel economy, rough idling, and a noticeable decrease in engine performance.
2. What are the possible causes of OBDII code P0051 in a Subaru indicating HO2S21 Heater Control Circuit Low?
- The code P0051 can be triggered by a faulty oxygen sensor, damaged wiring or connectors, or issues with the vehicle's ECM.
3. How can I diagnose OBDII code P0051 in a Subaru for the HO2S21 Heater Control Circuit Low?
- Diagnosing this code usually involves checking the oxygen sensor for resistance, inspecting the wiring for damage, and testing the sensor's heater control circuit.
4. Can a dirty oxygen sensor cause OBDII code P0051 in a Subaru for HO2S21 Heater Control Circuit Low?
- Yes, a dirty or contaminated oxygen sensor can lead to improper heater control circuit operation, triggering the P0051 code.
5. What are some repair tips for addressing OBDII code P0051 in a Subaru related to HO2S21 Heater Control Circuit Low?
- Repair tips may include replacing the faulty oxygen sensor, repairing damaged wiring, and ensuring proper connectivity of all related components.
6. Is it safe to continue driving a Subaru with OBDII code P0051 for HO2S21 Heater Control Circuit Low?
- While the vehicle may still operate, it is recommended to address the issue promptly to prevent potential damage to the engine and ensure optimal performance.
7. Can resetting the OBDII code P0051 in a Subaru for HO2S21 Heater Control Circuit Low solve the issue?
- Resetting the code may temporarily clear the warning light, but it is essential to diagnose and repair the underlying problem to prevent the code from reoccurring.
8. How much does it typically cost to repair OBDII code P0051 in a Subaru related to HO2S21 Heater Control Circuit Low?
- The cost of repair can vary depending on the root cause of the issue, but it may involve expenses related to parts and labor, typically ranging from $100 to $300.
9. Are there any preventive measures to avoid triggering OBDII code P0051 for HO2S21 Heater Control Circuit Low in a Subaru?
- Regular maintenance checks, such as inspecting the oxygen sensors during tune-ups, can help prevent issues that lead to the P0051 code.
10. Can a DIY enthusiast fix OBDII code P0051 in a Subaru for HO2S21 Heater Control Circuit Low?
- Depending on the individual's mechanical skills and access to tools, some DIY enthusiasts may be able to address the code by following repair guides or tutorials specific to the issue.
Discuss the causes and fixes for P0051 Subaru OBDII Code
-
The P0051 code is thrown when the O2 sensor on the DRIVER's side (LH) of a USA Subaru has a broken heater circuit. To test it, unplug the wire to the sensor and put an ohmmeter on the two upper pins of the sensor. If it is over 10 ohms, the heater on the sensor is bad.
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