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P0038 Code – What Does This Mean & How to Fix

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

Error code P0038 is described as the HO2S (Heated Oxygen Sensor) High Bank 1, Sensor 2 heater system. It is a general term that usually implies that the heating element circuit of the HO2S has a problem.

Meaning

In modern vehicle engines, oxygen sensors with a heating element are widespread. The heated oxygen sensors (HO2S) data are used as inputs by PCM (Powertrain Control Module) to detect the contents of oxygen in the exhaust system.

The PCM primarily uses the information gathered from Bank 1,2 HO2S to monitor catalytic converter efficiency. A heating element is crucial to this sensor. Whilst an oxygen sensor was a single wire sensor in pre-OBDII cars; now a four wires sensor is more common. Two wires dedicated to the oxygen sensor and two dedicated to the heating element. The oxygen sensor warmer simply reduces the time required for a complete loop. The PCM checks the heater on time. The PCM checks the heater circuits continually for aberrant voltages or even for abnormal amperages in some instances.

Oxygen sensors analyse the quantity of oxygen in the exhaust stream and forward their data to the control module (PCM). This data directs adaptations to the operational parameters of the engine, such as air and fuel consumption, to optimize its performance.

When the PCM identifies the heater circuit with an unusually high voltage state, P0038 can be set. This code only refers to half of the oxygen sensor heating circuit.

Causes

  • Potential causes of a P0038 code include: 
  • Defective Bank 1,2 HO2S (Heated Oxygen sensor)
  • The heater control circuit is open (12-volt PCM controlled systems)
  • In the heater control circuit, short to B+ (battery voltage) (12-volt PCM controlled systems)
  • There is an open ground circuit (12-volt PCM controlled systems)
  • Heater control circuit shorted to ground (On PCM ground-controlled systems)
  • Burned wire as a result of wiring running too close to hot exhaust components.
  • Blown fuses on the heating control circuit (if applicable) 
  • Short circuits produced by burned wire 
  • Bad connections caused by corrosion or impact damage caused by road debris.

Note that vacuum leaks that cause unmetered air to enter the engine are more likely to cause oxygen sensor range/performance issues than high input voltages in the control circuit.

Symptoms

The PCM monitors the catalytic converter's performance by analysing the post-catalyst oxygen sensor values. While code P0038 will not cause significant damage to your vehicle, it may create noticeable symptoms such as the following:

  • Also Check Engine Light (CEL) that is lit.

Symptoms will vary significantly. Certain cars will operate in a wealthy state, while others will operate in a lean state at all times. Additionally, the P0038 code indicates decreased engine power and choppy idling. It is fairly unusual to observe black smoke coming from the exhaust in conjunction with a check engine light.

Diagnosis

To troubleshoot this error code P0038, one must follow the instructions below.

First of all, one needs to examine all wires and connectors linked to the components of the issue (heated oxygen sensor heater circuit control).

Then check for any evidence of burnt/shorted/damaged connections.

Once you know the problem of the broken components, go for the next step.

Also, check the related fuses during your first wiring examination. Keep in mind that the fused circuit B requires the input voltage for some applications.

Now, if the error code continues, the continuity and resistance checks of all wirings related to the components of the problem will be performed.

You will then have to check for evidence of discolouration or deposits on the oxygen sensors. You must remember that the oxygen sensor of any deposits can't be cleaned. The only solution feasible is to replace the sensor and use premium oil and gasoline that does not include additives.

Finally, check again to see if error codes remain.

Common mistakes

Though troubleshooting this error code, the most common error that people are likely to make is to replace the oxygen sensor even when this is not a defect. It was not oxygen sensors that were at the basis of the problem but lean or rich engine conditions, which caused wrong results.

Another typical error might be that the incorrect oxygen sensor is replaced.

How serious is this?

The DTC P0038 is linked with an oxygen sensor, one must take this error very seriously. It could decrease the engine capacity. Fuel consumption may be increased, and due to faulty air to fuel ratio, the vehicle may show smoky exhaust. 

What repairs can fix the code?

These fixtures are used to fix the DTC P0038 code error.

  • Check the exhaust system and its components. If one wants to fix this problem one cannot do much other than replacing the oxygen sensor and related elements (wire, connections etc) if they are broken. 
  • If the wire and connections are in a good condition, the HO2S bank 1 sensor 2 must be switched off to check for 12V B+.
  • Also, verify whether or not the heating control system is intact. If it is intact, the oxygen sensor must be replaced. Replace the oxygen sensor in case of infinite resistance.

One must use the ohmmeter and perform a heating element resistance test.

Check the PCM whether it is working properly or not. Repair it in case of non-functionality. 

Related codes

Other related error codes to the DTC P0038 are

  • P0043 - HO2S Heater Control Circuit Low (Bank 1 Sensor 3
  • P0447 - Evaporative Emission Control System Vent Valve Solenoid Circuit Open
  • P0491 - Secondary Air Injection System Insufficient Flow Bank 1
  • P0122 - Throttle Position Sensor/Switch A Circuit Low Input
  • P0352 - Ignition Coil B Primary/Secondary Circuit Malfunction
  • U0073 - Control Module Communication Bus A Off
  • P0158 - 02 High Voltage Circuit Sensor (Bank 2, Sensor 2)
  • P0200 - Fuel Injector Circuit Malfunction
  • P0522 - Engine Oil Pressure Sensor/Switch Low Input
  • P0409 - Exhaust Gas Recirculation Sensor "A" Circuit
  • P0051 - Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1)
  • P0720 - Output Speed Sensor Circuit Malfunction
  • P0032 - DTC (Diagnostic Trouble Code) Refers to the O2 Sensor (Oxygen Sensor) Located On Bank 1 in Front of The Catalytic Converter
  • P0031- Code is: Oxygen Sensor Heater Control Circuit Low Bank 1 Sensor 1
  • P0033 - Is a Diagnostic Trouble Code (Dtc) For "Turbocharger or Supercharger Bypass Valve Control Circuit"
  • P0037 - HO2S Heater Control Circuit Low Bank 1, Sensor 2

Conclusion

DTC P0038 is not an error that can be overlooked or ignored. One must take this code error seriously. The code error P0038 can damage the engine working and performance. An expert with dedicated tools can solve this issue. It is recommended to check your vehicle with an expert if you are facing any above-mentioned symptoms related to this DTC error.

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