P2001 OBD-II Trouble Code: NOx Trap Efficiency Below Threshold Bank 2

P2001 trouble code definition

The P2001 diagnostic trouble code indicates that the NOx trap efficiency threshold for bank 2 is below the normal operating threshold.

Related Trouble Code:

P2000 OBD-II Trouble Code: [NOx Trap Efficiency Below Threshold Bank 1]

What the P2001 code means

The purpose of the NOx trap is to absorb nitric oxide and nitrogen dioxide so that emissions of these harmful gases can be significantly reduced before being released through the catalytic converter. Oxygen (O2) sensors provide data to the powertrain control module (PCM) about the exhaust composition and temperature. This data is then used by the PCM to determine the efficiency of the NOx trap.

The upstream oxygen sensor readings will change as the fuel mixture conditions change. The downstream oxygen sensor readings will remain steady. If PCM is unable to determine the efficiency of the NOx trap based on the readings provided by the upstream and downstream oxygen sensors, it will store the P2001 diagnostic trouble code and the Check Engine Light will come on.

What causes the P2001 code?

• Faulty catalytic converter
• Faulty oxygen sensors
• Faulty mass airflow (MAF) sensor
• Faulty manifold air pressure (MAP) sensor
• Faulty coolant temperature sensor
• Faulty fuel pressure regulator
• Faulty fuel injector
• Broken upstream exhaust
• Intake manifold gaskets that are leaking
• Using the wrong fuel for the car
• Engine misfire

What are the symptoms of the P2001 code?

• Check Engine Light is on
• Engine may hesitate
• Engine may make hissing noises when accelerating
• Engine may experience a lack of power
• Engine may stall
• Engine may fail to start

How does a mechanic diagnose the P2001 code?

• Start by checking to see if your catalytic converter is still under warranty. Federal law mandates that catalytic converters carry a 100,000 mile warranty, regardless of the age of the vehicle.

• Check the exhaust in front of the catalytic converter for damage. Fix the exhaust and retest for diagnostic trouble code P2001.

• Inspect all of the wiring and connectors for damage. Repair or replace damaged wiring and/or connectors as necessary and retest for diagnostic trouble code P2001.

• Use an OBD-II scanner and collect freeze frame data as well as all diagnostic trouble codes that have been stored by the powertrain control module.

• Clear the stored diagnostic trouble codes and complete a test drive to see if the code comes back.

• If the code does not come back immediately, an intermittent problem may exist.

• Begin by testing the temperature of the catalytic converter. Bring the engine to normal operating temperature and use an infrared temperature gun to read the temperature of the catalytic converter.

• It can be determined that the catalytic converter is bad, if the temperature of the catalytic converter is higher than the manufacturer specifications.

• If the temperature of the catalytic converter is considered normal based on the manufacturer specifications, it will be necessary to check the operation of the oxygen sensors that are positioned in front of the catalytic converter and behind it (upstream/downstream).

• View live data to observe the operation of the upstream and downstream oxygen sensors. If operating normally, the upstream oxygen sensor will give a voltage reading then quickly switches back and forth from .350 volts and .900 volts. A downstream oxygen sensor that is operating normally will give a steady voltage reading of around .500 volts.

• If the voltage readings of the upstream and downstream oxygen sensors are not normal, this could be an indication that the oxygen sensors are faulty. Usually when the oxygen sensors are faulty, an oxygen sensor diagnostic trouble code will be stored along with the P2001 diagnostic trouble code.

Common mistakes when diagnosing the P2001 code

• Other codes are usually stored by the PCM, along with the P2001 diagnostic trouble code, and neglecting to diagnose these codes is a common mistake.

• Catalytic converter failure is usually caused by another component, so it is important to diagnose these trouble codes before replacing the catalytic converter.

• It is also important not to replace the oxygen sensors without being certain that they are faulty.

How serious is the P2001 code?

• Most of the time, the P2001 diagnostic trouble code does not affect driveability and is therefore not considered serious.

• This code should be diagnosed and repaired in a timely manner, especially if driveability problems are present, as to not damage other engine components.

What repairs can fix the P2001 code?

• Replace faulty catalytic converter
• Replace broken exhaust (this should be done before determining the catalytic converter needs replacement)
• Replace faulty coolant temperature sensor
• Replace faulty oxygen sensor
• Replace faulty mass airflow (MAF) sensor
• Replace faulty manifold pressure (MAP) sensor
• Replace faulty fuel pressure regulator
• Repair or replace intake manifold gasket
• Replace faulty fuel injector

Additional comments for consideration regarding the P2001 code

It is common for the catalytic converter to be replaced in error when there are other things causing the P2001 diagnostic trouble code. A faulty oxygen sensor, misfire in the engine, or a faulty coolant temperature sensor should be diagnosed and replaced before diagnosing and replacing the catalytic converter.

Need help with a P2001 code?

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