Damaged or corroded wiring or connector at the NOx sensor or along the supply circuit.; Blown fuse or faulty relay supplying power to the NOx sensor heater circuit.; High resistance in the supply circuit due to loose terminals or chafed wires.; Failed NOx sensor with an internal short or open in its supply circuit.; Faulty engine control module (ECM) driver for the sensor supply voltage, though this is rare.; Water intrusion or contamination in the connector causing voltage irregularities.; Aftermarket accessories improperly wired into the sensor circuit causing voltage drops.

DTC codes / P22xx · Fuel and air metering (injector circuits) / P220C

P220CNOx Sensor Supply Voltage Circuit (Bank 2 Sensor 1)

Q: What does code P220C mean?

NOx Sensor Supply Voltage Circuit (Bank 2 Sensor 1). P220C indicates that the engine control module has detected an abnormal voltage on the supply circuit feeding the nitrogen oxide (NOx) sensor located in bank 2, sensor 1. The computer monitors the voltage supplied to the sensor and sets this code when the circuit falls outside the expected range, which can prevent the sensor from operating correctly and may affect emissions compliance.

P220C indicates that the engine control module has detected an abnormal voltage on the supply circuit feeding the nitrogen oxide (NOx) sensor located in bank 2, sensor 1. The computer monitors the voltage supplied to the sensor and sets this code when the circuit falls outside the expected range, which can prevent the sensor from operating correctly and may affect emissions compliance.

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, though this is less common.
Increased fuel consumption as the engine may default to a less efficient operating strategy.
Possible rough idle or hesitation during acceleration in some cases.
Failure to pass an emissions inspection due to the stored code.
In rare instances, the vehicle may enter limp mode to protect the aftertreatment system.

Common causes, most likely first

Damaged or corroded wiring or connector at the NOx sensor or along the supply circuit.
Blown fuse or faulty relay supplying power to the NOx sensor heater circuit.
High resistance in the supply circuit due to loose terminals or chafed wires.
Failed NOx sensor with an internal short or open in its supply circuit.
Faulty engine control module (ECM) driver for the sensor supply voltage, though this is rare.
Water intrusion or contamination in the connector causing voltage irregularities.
Aftermarket accessories improperly wired into the sensor circuit causing voltage drops.

How to diagnose and fix it

Inspect the NOx sensor connector and wiring for damage, corrosion, or loose pins; clean or repair as needed.
Check the fuse and relay that supply power to the NOx sensor circuit and replace if faulty.
Measure the supply voltage at the sensor connector with the key on and engine off, comparing to manufacturer specifications.
Perform a voltage drop test on the supply circuit to identify excessive resistance in the wiring.
If the supply voltage is correct at the connector, test the NOx sensor itself for internal resistance or shorts according to service information.
Replace the NOx sensor if it fails electrical testing or if the supply circuit is confirmed good.
Clear the code and perform a road test to verify the repair and ensure the code does not return.

Before you replace the NOx sensor

A common oversight is assuming the NOx sensor is defective when the actual problem is a blown fuse or a corroded connector that interrupts the supply voltage.
The supply voltage circuit often shares a fuse with other components, so a blown fuse may cause multiple codes; always check for additional codes before condemning the sensor.
Voltage drops in the supply circuit can be intermittent and only appear under certain conditions, such as vibration or temperature changes, so wiggle tests are essential.
Some technicians replace the NOx sensor without checking the ECM's supply voltage output, leading to repeat failures if the ECM driver is weak.
This code can be set by a low battery or charging system issue that causes system voltage to drop below the sensor's operating threshold.

Can I keep driving with P220C?

You can generally continue driving with this code, but avoid long distances or heavy loads until it is diagnosed, as the vehicle may fail emissions testing and prolonged driving with a faulty NOx sensor can lead to reduced fuel efficiency or further aftertreatment damage.

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.