What it means
The heater sense circuit for the NOx sensor on Bank 1 Sensor 3 has an intermittent or erratic signal.
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 reports the Bank 1 Sensor 3 NOx sensor heater condition to the control module. P23BA sets when that signal becomes erratic or drops in and out instead of remaining stable, often because vibration affects a connector or harness connection.
Common causes
Most likely first.
- Intermittent contact at connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light
- Possible NOx or aftertreatment warning
- Increased NOx emissions or failed emissions test
How to diagnose it
- Use a scan tool to save freeze-frame data and note whether the Bank 1 Sensor 3 heater sense reading changes with engine vibration or operating conditions.
- Inspect the sensor connector, terminals, and harness supports for looseness, corrosion, chafing, or contact with a vibrating or hot component.
- Check connector pin retention and sense-wire continuity while gently moving the accessible harness, using the manufacturer's procedure.
- Monitor the sense reading in live data while safely reproducing the conditions that trigger the fault, if practical.
- If the connection remains stable, test the NOx sensor heater sense output and control circuit against the manufacturer's specification.
Common fixes
- Secure and reroute the Bank 1 Sensor 3 harness away from vibrating or hot components.
- Repair chafed insulation or a damaged section of sense wire.
- Clean or repair loose or corroded connector terminals.
- Replace the Bank 1 Sensor 3 NOx sensor if its heater sense output is intermittent during testing.
- Repair the heater sense control circuit if the sensor and harness pass checks.
Can I keep driving?
Cautious driving is generally possible if the engine and exhaust system operate normally, but emissions may rise and an aftertreatment warning or emissions test failure may follow. Avoid delaying diagnosis if the warning becomes persistent or other exhaust warnings appear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.