P23B6: NOx Sensor Supply Voltage Circuit Bank 1 Sensor 3

What it means

The supply voltage to the bank 1 sensor 3 NOx sensor is outside the calibrated window.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The supply voltage circuit provides electrical power to the Bank 1 Sensor 3 NOx sensor or its control electronics. This code sets when the module detects supply voltage outside its calibrated window, which can result from unstable or low supply, high resistance, an open, or a faulty sensor or control module.

Common causes

Most likely first.

1. Low or unstable supply voltage
2. High resistance or an open in the supply wiring
3. Loose or corroded sensor connector
4. Fault in the NOx sensor or its control module

Symptoms

• Check engine light
• Possible NOx or aftertreatment warning
• Increased NOx emissions or failed emissions test

How to diagnose it

1. Review freeze-frame data and live supply-voltage information for Bank 1 Sensor 3 to see whether the fault occurs during startup, warm-up, or operation.
2. Inspect the Sensor 3 power connector and harness for corrosion, looseness, heat damage, or chafing.
3. Check the relevant supply and ground connections for looseness or corrosion that could cause unstable power.
4. Following the wiring diagram, measure supply voltage at the sensor connector under the conditions specified by the manufacturer and compare it with the manufacturer's specification.
5. If wiring and connections are sound, test the NOx sensor and its control module for an internal supply fault.

Common fixes

• Clean and secure a loose or corroded Sensor 3 supply connector.
• Repair an open, high-resistance, or damaged supply wire.
• Repair a poor ground connection affecting the sensor supply.
• Replace the Bank 1 Sensor 3 NOx sensor or control module if testing confirms an internal fault.

Can I keep driving?

If the vehicle runs normally, keep driving to necessary trips and arrange diagnosis soon. An unstable supply can disable or disrupt NOx readings, raise emissions, and trigger an aftertreatment warning.