Faulty NOx sensor supply voltage circuit, such as an open or short in the wiring or connector; Defective NOx sensor itself, causing excessive current draw or internal failure; Blown fuse or relay that supplies power to the NOx sensor circuit; Corroded, loose, or damaged electrical connectors at the sensor or PCM; PCM software issue or internal fault in the voltage supply circuit; High resistance in the ground circuit for the NOx sensor; Aftermarket or incorrect sensor installation that does not meet voltage requirements

DTC codes / P22xx · Fuel and air metering (injector circuits) / P220A

P220ANOx Sensor Supply Voltage Circuit (Bank 1 Sensor 1)

Q: What does code P220A mean?

NOx Sensor Supply Voltage Circuit (Bank 1 Sensor 1). P220A indicates that the powertrain control module (PCM) has detected an abnormal voltage condition on the supply circuit for the nitrogen oxide (NOx) sensor located in Bank 1, Sensor 1. The PCM monitors the voltage feed to the sensor and sets this code when the supply voltage falls outside the expected range, which can prevent the sensor from operating correctly.

P220A indicates that the powertrain control module (PCM) has detected an abnormal voltage condition on the supply circuit for the nitrogen oxide (NOx) sensor located in Bank 1, Sensor 1. The PCM monitors the voltage feed to the sensor and sets this code when the supply voltage falls outside the expected range, which can prevent the sensor from operating correctly.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine performance or power, particularly under load
Poor fuel economy due to incorrect air-fuel ratio management
Increased emissions, which may cause a state inspection failure
In rare cases, the engine may enter limp mode or exhibit rough running
No symptoms besides the warning light in many instances

Common causes, most likely first

Faulty NOx sensor supply voltage circuit, such as an open or short in the wiring or connector
Defective NOx sensor itself, causing excessive current draw or internal failure
Blown fuse or relay that supplies power to the NOx sensor circuit
Corroded, loose, or damaged electrical connectors at the sensor or PCM
PCM software issue or internal fault in the voltage supply circuit
High resistance in the ground circuit for the NOx sensor
Aftermarket or incorrect sensor installation that does not meet voltage requirements

How to diagnose and fix it

Verify the code with a scan tool and check for any related codes in the powertrain control module
Inspect the NOx sensor wiring and connectors for damage, corrosion, or loose pins
Check the fuse and relay that supply power to the NOx sensor circuit and replace if necessary
Measure the supply voltage at the NOx sensor connector with the key on and engine off, comparing to manufacturer specifications
Test the ground circuit for the NOx sensor using a multimeter to ensure low resistance
If voltage supply is correct, test the NOx sensor according to the manufacturer's procedure, which may involve resistance or signal checks
Replace the NOx sensor if testing indicates it is faulty, and clear the code to verify the repair

Before you replace the NOx sensor

A blown fuse for the NOx sensor heater circuit is a common cause that is often overlooked because the fuse may not be labeled clearly in the fuse box.
The supply voltage circuit can be affected by a faulty relay that intermittently drops voltage, which may not show up during a simple voltage check unless the circuit is loaded.
Corrosion inside the connector at the NOx sensor can cause high resistance and voltage drops that mimic a failed sensor, so always inspect connectors before condemning the sensor.
This code can be set by a PCM software glitch that misinterprets a momentary voltage dip, so checking for technical service bulletins before replacing parts is wise.
A weak battery or charging system issue can cause low supply voltage to the NOx sensor and set this code, so verify battery and charging system health first.

Can I keep driving with P220A?

You can generally continue driving with this code, but avoid heavy acceleration or long trips until it is diagnosed, as the vehicle may be running less efficiently and emitting more pollutants. If the engine enters limp mode or runs poorly, seek service immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.