Powertrain Code P0051-A complete analysis and possible fixes

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What does the P0051 code denote?

The vehicle error codes denote that there is something wrong going on in the vehicle’s system. There are thousands of vehicle error codes, and each of them signifies different problems. The owner of the vehicle may be in a stance after experiencing the code. Without any further ado, let us discuss the error code P0051. 

The DTC P0051 is  a powertrain code that determines the “HO2S Heater Control Circuit Low (Bank 2 Sensor 1).” This error code happened when the ECM felt that there was something faulty in the main heater oxygen sensor at bank number 2 and sensor number 1. 

The main responsibility of the oxygen sensor is to measure the exact amount of oxygen in the exhaust portion, and there might be some issues with the voltage of the Heater Control Circuit. The oxygen heater can control the air-fuel mix ratio, which is really a significant factor for the vehicle. If the air-fuel mix ratio is not at the optimum temperature or not in the standard proportion, then the shifting of the gear won’t be smooth and steady. Low or high oxygen sensor resistance may also cause the error code P0051. 

Popular brands showing the respective code:

In Some car brands, the error code P0051 is pretty common, like the Nissan P0051, Toyota P0051, Harley code P0051, P0051 BMW, Jeep P0051, Infiniti P0051 Lexus P0051, etc. 

Inspection procedure of HO2S Heater Control Circuit

You need to know the total inspection procedure of the Heater Control Circuit so that you can repair the defective part by yourself at home. Before inspecting, make sure that the air-fuel mixture is in the right proportion if the engine is heated up or not, etc.  

  • Check EFI relay

Check the EFI relay for any sort of defect. Remove the particular relay from the main engine and check for corrosion or rust. If the relay is bad, it may cut off the power supplied to the fuel pump, facilitating the stalling mode.How to test EFI relay

  • Checking the resistance

Apply a multimeter to check the resistance of the oxygen sensor. If it yields normal resistance, everything is good to go, but if it shows abnormal values, you need to repair the oxygen sensor if it shows abnormal values.check the resistance of the oxygen sensor

  • Examining the harness and connector

The first thing to do is to turn off the ignition key and disconnect the harness and connectors from their respective places. Then inspect the harness and connector of the oxygen sensor. After repairing, again reconnect the harness and connectors. Now everything is good, and you have successfully repaired the defective oxygen sensor.checking harness and connector

Complete Specification of HO2S Heater Control Circuit

The heated oxygen sensor (HO2S) heater decreases the time limit required for the oxygen sensor to get to the premium operating temperature. It monitors the operating temperature during extended unwanted idle periods. If the ignition is turned on, then the voltage of the ignition is carried out directly to the heater of the sensor. The engine control module (ECM) administers the operation of the heater by first regulating the control circuit to the ground station when the sensors are out of order. This impedes the probability of thermal shock to the sensor from condensation buildup on the sensor by controlling the sensor’s rate of heating.

After a predetermined time, the ECM commands the heaters to be on continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to the ground to maintain the desired temperature. The ECM administers the heater by supporting the control circuit with a solid-state device which is called the driver. The driver is facilitated with a feedback circuit that is pulled up to voltage. The ECM can sneak out if the control circuit is open, close, or shorted to the ground. Suppose the ECM finds that the control circuit voltage is lower than a predetermined value when the circuit is commanded to turn off. That is the complete background of the heated oxygen sensor (HO2S) heater. 

Working Mechanism of HO2S Heater Control Circuit

The oxygen heater control system works at an optimum temperature. If the temperature is not up to the mark, then it may fail to work. The working mechanism of the heater oxygen control system is straightforward and simple. The vehicle needs to shift the gear during driving to accelerate the speed and velocity. And forgoing the gear, it is crucial to maintain the actual air-fuel mix ratio, which is supplied by this portion of the vehicle supplies. The oxygen sensor creates that optimum heat so that the oxygen chamber can work properly. The circuit heater denotes a 12-volt voltage. If the voltage is not harmonious with the standard value, then repair the voltage of the oxygen chamber. A ground circuit that is operated in the direction of the oxygen sensor is usually administered by the ECM. All these combinations in the oxygen heater chamber make it possible to work effortlessly.

The exact location of the HO2S Heater Control Circuit

The location of the car parts is not always the same for the different car models. It varies from car model to model. But the most common location of the HO2S Heater Control Circuit is at the main exhaust manifold that administers the total amount of oxygen entering the exhaust unit. The main oxygen Heater Control Circuit comprises,

  • Rear Muffler and rear cat
  • Front tube assembly
  • HO2S1-B1 Front O2 sensor B1
  • HO2S1-B2 Front O2 sensor B2
  • HO2S2-B1 rear O2 sensor B1
  • HO2S2-B2 rear O2 sensor B2
  • Exhaust manifolds
  • Catalytic convertor

Car parts associated with DTC P0051:

The causes can be enormous behind the occurrence of the error code P0051. A lot of car parts are associated with the DTC P0051. Here we will show some of those parts for the convenience of the readers, 

  • Catalytic converter 

The most significant part behind the occurrence of the DTC P0051 is the damaged Catalytic converter which can be far more complex. The internal combustion system uses the exhaust gas exterior to spend the gasses. Here are the main parts of the catalytic converter,  catalytic converter problems

  • The gas inlet contains carbon monoxide, nitrogen oxide, hydrogen chloride, etc.
  • The catalytic substrate, End seal, packaging mat, steel shell
  • A system outlet emits water vapor, carbon dioxide, nitrogen, and oxygen.  

There are some essential conditions for the proper working mechanism of the catalytic converter. Those factors are the optimum temperature, cold-start emissions, catalyst conversion efficiency, pressure amount, actual surface areas, air-fuel equivalence ratio, rate of the reaction, and so on. The catalytic converter plays a pivotal role in reducing the emission of bad fumes. The honeycomb, washcoat, and catalyst support combinedly operate the entire process.  

  • The heater circuit fuse 

The damaged heater circuit fuse can reduce the overall workability and usability of the entire engine. If the fuse deteriorates, then replace it without any further delay. 

  • Heated oxygen sensor 

The heated oxygen sensor is very much responsible for the smooth operation of the oxygen chamber. It controls the perfect air-fuel proportion, engine combustion levels, The shifting of the gears, and rotation of the camshaft and crankshaft. If the sensor misbehaves, then replace the sensor without any delay. Oxygen Sensor Heaters

  • The heated oxygen sensor connector 

There are varieties of oxygen sensor connectors, and most of them are compatible with the ground sensors but not for the isolated sensors. The connectors are the bridge between the oxygen sensor and the main engine compartment. So replace the connector if it gets damaged.  

  • Heated oxygen sensor harness 

A deteriorated oxygen sensor harness is a real threat to the vehicle, So give a close look at the harness to see if it is operating smoothly or not. 

  • The blood life: ECM

The engine control module is the primary coordinator between the different parts of the vehicle. All the information and signals come to the ECM for proper evaluation so that the vehicle can be operated smoothly, and the rotational movement information of the camshaft, smooth OCV, wiring and connectors, and sensor data all are evaluated by the ECM. Replace the entire ECM if it is out of order.

  • The electric wirings and sensors 

The electric wirings and the circuits are the main factors behind the flawless operation of the engine. If you notice something fishy in the wirings or if the sensors fail to convey the real information about the strategic surge, then it is time to change the sensors And the wirings. Electrical wiring of sensors

The Possible symptoms

You might be confused about the possible symptoms of the error code P0051. Here I will discuss some of the common symptoms so that you can detect the DTC P0051, 

  • The check engine light has been illuminated, or the malfunction indicator light has been activated. 
  • The overall fuel consumption is increasing at an unstoppable rate
  • The fuel economy is decreased drastically
  • Your car may not pass the emission test, and dangerous black and white smoke are emitted from the tail exhaust pipe.
  • The engine may show stalling, and limp mode may have been activated, which means that the system has stopped the operation of the main engine.
  • There may be a leakage in the exhaust valve. The vehicle may run rough or may produce unwanted rattling noise. These are some of the major symptoms of the error code P0051 

Causes of DTC P0051

The DTC P0051 is a destructive code for the vehicle as it is solely related to the oxygen Heater Control Circuit. Let us see some of the influential causes behind the occurrence of this code,

  • The excessive dust and debris may damage the wirings and the connectors 
  • The oxygen sensors may be out of order and cannot carry the necessary information to the ECM or to the main computer.
  • Failure in the ground wire sensors may exert the fault code P0051
  • The fuses of the circuit may be blown out due to excessive heat or abrasion, friction, and many other factors.
  • The car may be using the wrong viscosity oil, the fuel pressure may be insufficient, or the engine fuel level is not up to the mark.
  • The air-fuel ratio in the main combustion engine may be inappropriate. The main computer or the ECM may be out of order and can not read the signals and data.

How devastating is this code?

It is needless to say that almost all the powertrain codes are dangerous for the vehicle’s health. The trouble code P0051 is no exception. If you ignore this code for a long time, it will be proven a devastating issue for your vehicle. A long-term disguised fault code may slow down the car’s speed. The fuel consumption may exceed the normal limit, and the engine may show poor accuracy. This can also damage the whole engine portion, which will be a massive cost for the car owner. Internal damage to the wirings and the circuits may also cost a large number of dollars. All in all, the gear shifting operation may be thwarted, which creates an unnecessary stumble during driving.

Complete diagnosis procedure:

The diagnosis process of the error code P0051 is extensive. Here, synchronization and maintaining the hierarchy are crucial. If you do not maintain the order in diagnosis, it will waste all your efforts. Here is the complete process of the diagnosis that is described in maintaining the order, 

  • The very initial step is to implant a smart OBD2 scanner tool with the main socket of the vehicle that is situated underneath the dashboard. Then check for the error codes. There may be more than one error code illuminating the scanner’s screen. Solve the error codes by following the necessary guidelines.
  • After you have found the code, then take a test drive of the vehicle and try to eliminate the code by pressing the delete code option. If this does not diminish the error code, then dig deep into the alternatives.
  • Inspect the freeze frame data and check what the possible codes are and what are the affected locations in the vehicle. 
  • Diagnose the wirings and the connectors if they are facing any kind of discontinuation or tear. Check the performance of the sensors. The sensors must be able to convey the respective information to the ECM. 
  • Diagnose the oil control valve and the level of the engine oil. Then examine the oxygen Heater Control Circuit; if you find any type of leakage, then repair the unit. 
  • Finally, diagnose the ECM and see if it can read the data provided by the different parts of the vehicle. 

Common mistakes in diagnosing the P0051 code

Many inexperienced car owners make silly mistakes while diagnosing the fault code by themselves, and even some professional mechanics make obvious mistakes during the trouble code diagnosis. In case you can avoid those mistakes, here I will depict the common mistakes during diagnosis, 

  • The mechanic may skip the most crucial and basic steps during diagnosis, which is the visual inspection of the vehicle. He needs to examine all the suspected parts visually. Sometimes they just replace the damaged parts without visually checking the defective parts.
  • The auto mechanic may skip checking the engine fuel level and viscosity. Insufficient fuel may hamper the other parts of the vehicle.
  • They may overlook measuring the voltage and the resistance of the heated oxygen sensor. This might create ample opportunities for the error code to wreak havoc within a short period of time. 
  • Checking the ignition and the ECM is mandatory. You can not skip this while diagnosed.

These are some of the unintentional mistakes that can happen quite frequently. To have an error-free car, you must avoid these trivial mistakes. 

How to Solve Error code P0051?

The fixing process of the trouble code P0051 is very time-consuming. You need to consult an expert to resolve the error code. Here I will depict the complete process of repairing the error code in some consecutive steps,

Step-1: Read the freeze frame data 

The very initial step is to check for the codes by connecting the OBD2 scanner with the OBD2 port that is situated near the driver’s seat. After you connect the OBD2 scanner with the port, it scans the whole system of the vehicle. If it finds any fault, it will show it to the scanner’s screen. Another fantastic facility is the freeze frame data, and you can see this data as many times as you want as the scanner freezes that data for you. Check the live stream data and find out the faulty positioning of the car.

Step-2: Repair the wirings and the connectors

The most significant step is checking and repairing the oxygen sensors and circuits. Sometimes the electrical circuits face discontinuation due to some unavoidable issues. Due to dire corrosion, friction, and rust, the wirings may be damaged. A short circuit may disrupt the natural flow of the data through the wirings. Repairing Electrical Wiring

Step-3: Repair the voltage and resistance

One of the most crucial steps is to repair the voltage and resistance of the oxygen sensor. The standard voltage of the oxygen sensor is 12.6; measure the voltage by using a voltmeter. Connect the black And red wires to the opposite sides of the oxygen chamber. If the voltmeter gives a standard value, your oxygen sensor is alright, but if the reading exceeds the standard value, it needs repairing by following the same process, measuring the resistance, and repairing the defected part if needed.

Step-4: Check and replace the catalytic converters

This is the most crucial part of the oxygen sensor. The catalytic converters reduce the harmful effects of the toxic gasses and convert them into water vapor and other non-harmful products that reduce pollution in many aspects. Check and replace the defective catalytic converters to have a secured and eco-friendly vehicle.Catalytic Converter Replacement Time

Step-5: Replacement of the PCM

The PCM is the main component that controls the entire operation of the main engine. Sometimes the software is outdated, and it needs a proper update to bring back the initial glory of the PCM. So give the PCM a fresh factory reset. 

Other codes harmonious with DTC P0051

You may encounter several other fault codes similar to the fault code P0051. The repairing process is almost the same for all these fault codes; some of the similar codes are, 

P0030 stands for the “HO2S Heater Control Circuit (Bank 1 Sensor 1).”

P0031 denotes the “HO2S Heater Control Circuit Low (Bank 1 Sensor 1).”

P0032 means “HO2S Heater Control Circuit High (Bank 1 Sensor 1).”

These fault codes are very close to the trouble code P0051 as each of them is related to the HO2S Heater Control Circuit; the difference is that they are just the different portions of the oxygen sensor. Follow this article to generate a basic idea about these related codes and their repairing.

Final Overview

Terminating the error code P0051 is not a piece of cake. It needs dedication, hard work, and experience to eliminate the trouble code. If you are a new car owner and in a stance on solving the code, you can undoubtedly rely on this descriptive article. It will give you proper guidelines on fixing the error code at home without spending an extra penny. Follow the guidelines and let us know if you have successfully encountered the error code.

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