Error Code P2238 is defined as O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 1. A problem usually caused by a wiring short to ground, error in HO2S wiring, short to positive, or PCM issue.

This error code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.


Error Code P2238 happens where then is an open or short in the Air-Fuel sensor circuit, or if the Air-Fuel sensor output drops from its recommended figures. To detect this problem, the voltage of the A/F sensor is constantly monitored as soon as the ignition is switched On, and the admittance ( an electrical term that means the ease of flow of current) is checked while driving. If the voltage of the A/F sensor is between 0.6V and 4.5V, that means it is within the normal range. If the voltage is outside the specified range, or the admittance is less than the standard value, then the PCM will see it as a malfunction in the A/F sensor.

If the same malfunction is detected in the next drive cycle, the PCM will light up the Check Engine light and register the code in the vehicle’s memory system.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the memory system. The light is usually turned off if there are no other failures after three drive cycles.

For most manufacturers, this code will also cause the PCM to put the vehicle in failure mode fuel control. Other vehicle manufacturers cause the PCM to go into an open loop fuel control.

Possible Causes

There are a couple of factors that lead to this error code, such as:

  • Short in the internal heater circuit of O2 (Oxygen) sensor
  • Short circuit or corrosion in the connections of O2 sensor wiring connector
  • Shorted O2 sensor circuit grounds heater power relay

How to Check

Mechanics start their diagnosis of this code by using a scan tool to scan for codes and document the information from the PCM through its freeze frame data for failure.

Then, they will proceed in checking the O2 sensor heater circuit and compare it with other O2 sensors in the same control voltages and voltage input.

Next, they check the O2 heater circuit for open or short circuits in the sensor and relay.

Next, they test the O2 sensor wiring if it’s shorted to power relay or ground.

Lastly, they check the wiring harness for shorts or open circuits from the O2 sensor to the PCM.

How to Fix

Repairs for this error code are easy, but of course, require thorough diagnosis. Common repairs for this code include:

  • Replacement of the O2 sensor heater circuit that short-circuited
  • Repair of the wiring connector or O2 shorts in the O2 sensor wiring
  • Replacement of the power relay for the heater circuit that burned out or shorted that is indicated by the pinpoint test.
  • Replacement of the PCM if it is damaged by short in harness or damage in the sensor

The most common mistake in addressing this code is not verifying the failure before replacing the O2 sensor. Also, many people jump in to replacing the O2 sensors when the fault is caused by a short in the wiring.

Since this code indicates that the O2 sensor heater circuit is shorted causing circuit voltage control to be low, it will cause the PCM to put failure mode or open loop fuel control, as the fuel feedback control is not working properly. This, of course, causes the vehicle to fail emission tests.