P23B5: NOx Sensor Heater Sense Circuit Range or Performance Bank 1 Sensor 3

What it means

The heater sense circuit for the NOx sensor on Bank 1 Sensor 3 is outside its expected performance range.

At a glance

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

How it works

The heater sense circuit provides feedback about the Bank 1 Sensor 3 NOx sensor heater so the control module can judge whether it is performing as expected. This code sets when that feedback falls outside its expected performance range, which can reflect heater or sense-circuit degradation, high resistance, an intermittent connection, or a control module fault.

Common causes

Most likely first.

1. NOx sensor heater or sense circuit degradation
2. High resistance in the heater sense wiring or connector
3. Intermittent connection at the sensor
4. Heater control module fault

Symptoms

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

How to diagnose it

1. Check freeze-frame data and live heater feedback for Bank 1 Sensor 3 to see whether the out-of-range reading occurs during warm-up or persists.
2. Inspect the Sensor 3 connector and heater sense wiring for corrosion, loose terminals, chafing, or heat damage.
3. Check whether the heater feedback changes as the sensor warms using scan-tool data and the manufacturer's operating procedure.
4. Test heater sense circuit resistance and continuity, and compare results with the manufacturer's specification.
5. If the circuit is sound, test the Sensor 3 heater and heater control module for degraded or inconsistent operation.

Common fixes

• Repair a loose or corroded Sensor 3 connector or high-resistance sense-wire connection.
• Repair chafed or heat-damaged heater sense wiring.
• Replace the Bank 1 Sensor 3 NOx sensor if its heater or sense circuit is degraded.
• Repair or replace the heater control module if testing isolates the fault there.

Can I keep driving?

If the vehicle runs normally, use it only as needed until the heater feedback fault is diagnosed. The sensor may heat or report inconsistently, compromising NOx monitoring and emissions control.