Error Code P0130 is defined as Oxygen (O2) sensor Circuit Malfunction, Bank 1 Sensor 1. Meaning, the vehicle may have anywhere up to five O2 sensors and the PCM (powertrain control module, also referred as ECM or engine control module in some vehicles) has detected a problem, as the response of voltage signal from the sensor is taking more time than expected/specified. This causes the activation of the Check Engine light.

This code is a generic trouble code, meaning it is applicable to all vehicles made since 1996 up to present. It is related to P0131, P0132, P0133, P0134, P0135, P0171, or P0175.


The job of the O2 sensor is to produce a voltage based on the O2 content of the exhaust. This varies between 0.1 to 0.9V, with 0.1 indicating lean and 0.9 indicating rich. The PCM monitors the voltage while in closed loop to find out how much fuel it needs to inject.

If the PCM determines voltage level in O2 sensor to remain below 0.4 V (400 millivolts) for around 20 seconds (differs from one make and model to another) or the Air Fuel Ratio sensor to remain in lean-biased mode for too long (again, depends on the make and model of the vehicle), then the error code Error Code P0130 is set.

Common Symptoms

Depending whether the problem is erratic or not, there may be no symptoms aside from the activation of the Check Engine light. If the problem is continuous, then the common symptoms would be:

  • Engine running rough, misfiring and/or stumbling
  • Engine dies
  • Possible stalling or idle
  • Black smoke coming out from the tailpipe
  • Poor fuel economy

Possible Causes

The most common cause for P0130 is a bad O2 sensor, especially if it’s old and has not been replaced. But as with most error codes, there’s not always one reason. Other possible causes include:

  • Corrosion in water connector
  • Connector has loose terminal or plug is disconnected
  • Burnt wiring on exhaust components
  • Damage in the sensor wiring to the PCM
  • Open or short in the wiring caused by rubbing of engine components
  • Fuel system has poor volume to the engine (fuel pump or others)
  • Vacuum leak in the intake
  • Unmetered vacuum leak in the engine
  • Exhaust holes causing unmetered oxygen to get into the exhaust system
  • Out of range reading of MAF (Mass Airflow) sensor
  • Out of range reading of MAP (Manifold Absolute Pressure) sensor
  • Leaks in EVAP (Evaporative emission)
  • Leaking fuel pressure regulator
  • Bad PCM (rare)

How to Check

Error Code P0130 is pretty easy to diagnose, and as with other error codes, it requires a scan tool with sensor readings. A qualified technician will use the scan tool to read and determine the problem. He will start by clearing the code and take the vehicle for a test drive while duplicating the conditions when the code was set, such as load, speed, RPM etc, and monitor the scan tool if the error code comes back.

Based on the conditions of the tests, further diagnosis may be needed to fully understand the situation, and may require multiple electrical tools, such as an advanced scan tool for the PCM, digital meter with attachments, and smoke machine to detect leaks in the intake system.

How to Fix

With the help of the scan tool, determine whether the Bank 1 Sensor 1 is switching properly. It should switch quickly and evenly between rich and clean.

  1. If it switches properly, that means the problem is intermittent. Check the wiring for any visible damage. Then, conduct a wiggle test and check the connector and wiring while checking the O2 sensor voltage. If the voltage drops, then fix the part of the wiring harness where the problem is.
  2. If it doesn’t switch properly, make sure the sensor is getting an accurate reading of the exhaust. You can do this by briefly removing the fuel pressure regulator vacuum supply. The reading from the O2 sensor should be rich, as it reacts to the added fuel. Reinstall the regulator supply and then remove a vacuum supply line to induce a lean condition. The O2 sensor should read lean, as it reacts to the enleaned exhaust. If the sensor runs properly, that means the sensor is in good condition, and the problem may be caused by holes in the exhaust or unmetered vacuum leak from the engine. If you have checked the exhaust and there are no holes, there’s a chance the O2 sensor is misreading the exhaust due to the extra oxygen that enters the pipe through the holes.
  3. If the O2 sensor is simply not switching or sluggish, unplug it and make sure there’s the 5V reference voltage. Then, check the O2 heater sensor circuit for 12V supply. Also, check the ground’s continuity from the ground circuit. If there’s no proper voltage, there’s something missing or not in proper voltage, then check for open or short wire and repair appropriately. Without the right voltage, the Oxygen sensor will not run properly. If there is proper voltage, then you may need to replace your O2 sensor.

This code is pretty serious, as it doesn’t only cause poor fuel economy and prevent your vehicle from passing emission tests, but may also expose your engine to further risk of damage. It can also damage catalytic converters, which can be pretty expensive.