What Does Engine Code P2A00 Mean?

Engine code P2A00 indicates that there is a problem with your car’s O2 sensor.
Written by Brittni Brinn
Reviewed by Melanie Reiff
If your car is showing engine code P2A00, it means that your car’s powertrain control module (PCM) has detected a problem with the oxygen (O2) sensor.
Diagnostic trouble codes (DTC) indicate the type of problem or malfunction in your vehicle. A P2A00 engine code will show up if there is a problem with your O2 sensor. Your car needs the O2 sensor to function to keep your engine running at maximum efficiency.
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What does engine code P2A00 mean?

Definition: O2 [Oxygen sensor] sensor circuit range/ Performance bank 1 Sensor 1
The P2A00 engine code will appear if the PCM registers erratic or abnormal voltage from circuits connected to the O2 sensor. Performance bank 1 refers to the bank of cylinders where sensor 1 is located—in most cases, upstream from the catalytic converter.
The O2 sensor monitors the amount of oxygen in the exhaust system and lets the PCM know if the air-fuel (A/F) ratios need to be adjusted. The sensor requires a certain temperature to work, and the O2 sensor will not be able to send data to the PCM if the heating circuit is compromised. 

How much will it cost to fix?

The cost to fix a P2A00 engine code will vary depending on the exact nature of the repair, the make of your vehicle, and your location. It will take a mechanic about an hour to diagnose what is causing the P2A00 engine code. 
Labor costs may range from $75 to $150 per hour, depending on where you take your car for repairs. If the
oxygen sensor
cannot be fixed, a replacement will cost anywhere from $60 to $300.
MORE: Should you take your car to a repair shop or a mobile mechanic?

What can cause the P2A00 engine code?

Most problems associated with P2A00 have to do with your car’s O2 sensor. 
The primary function of the O2 sensor is to monitor the levels of oxygen in your car’s exhaust. It sends data to the PCM, which then makes adjustments to the air-fuel ratio in the engine. The O2 sensor makes sure your engine is operating at top efficiency.
O2 sensors also prevent fuel and vacuum leaks. If the sensor fails, your fuel efficiency may drop and your vehicle may fail future emissions tests.
There are a few potential causes for a P2A00 engine code:
  • Failed O2 sensor or A/F ratio sensor
  • A failed electrical connector to the O2 sensor
  • Blown fuse in the sensor circuit
  • Faulty or shorted-out wires in the sensor circuit
  • Low or excessive
    fuel pressure
  • Vacuum or exhaust leak
Key Takeaway The O2 sensor has a major impact on how the PCM determines how much fuel to inject into your engine.

Common symptoms of the P2A00 engine code

If your
check engine light is on
and you have a P2A00 engine code, you can expect to see these other symptoms as well:
  • Reduced fuel efficiency
  • Failed emissions test
  • Erratic idling
  • Rough engine or trouble accelerating
In rare cases, your engine may stall or fail. To avoid these symptoms, make sure you take your car in for repairs if your car shows a P2A00 code.
MORE: How to pass emissions testing

How serious is the P2A00 engine code?

A P2A00 is a serious problem that can greatly reduce your engine’s performance and lead to failed emissions tests. It can also affect your driving experience by inhibiting acceleration and making your engine run “rough” and erratic.
Key Takeaway The O2 sensor keeps your engine running at top efficiency and keeps your car’s emissions low.

Can I fix the P2A00 engine code myself?

Because a P2A00 engine code includes possible exhaust leaks along with O2 sensor problems, it’s best to have a trained mechanic diagnose the cause of a P2A00. Replacing the O2 sensor yourself may not solve the problem and could end up ignoring leaks that will cause further problems down the line.

Replacing the O2 sensor

If you have the necessary mechanical experience, here’s how to replace a faulty O2 sensor yourself:
  • Connect your OBD II scan tool to your vehicle to determine which oxygen sensor needs to be replaced. 
  • Use a jack and jack stands to raise your vehicle. Make sure the correct oxygen sensor is accessible.
  • Disconnect the oxygen sensor connector.
  • Use a wrench or oxygen sensor socket to loosen and remove the faulty oxygen sensor.
  • Install the replacement oxygen sensor and attach the sensor connector. Make sure that the replacement oxygen sensor is comparable to the old one and is the correct fit.
  • Clear the code using the OBD II scan tool
  • Start your vehicle. The code and Check Engine light should no longer appear and your car should run more smoothly.

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If your car fails an emissions test, you have to take your car in for repairs. The DMV will not renew the registration of a vehicle that doesn’t pass a smog or emissions test until the problem has been resolved.
The powertrain control module (PCM) acts as the brain of your car. It gathers information from sensors throughout your vehicle, like the O2 sensor, and makes adjustments to the A/F ratio in your engine. The PCM keeps your engine running smoothly and minimizes emissions.
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