P23BB

Code

Generic P — Powertrain

NOx Sensor Heater Resistance Bank 1 Sensor 3

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 46 RU: 22

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Failed NOx sensor heater element (internal open or high resistance)
Corroded, damaged, or disconnected heater connector or pins
Broken or shorted heater wiring harness (open, high resistance, or intermittent)
Poor ground or supply circuit to the heater (fuse, relay, PCM driver)
PCM or heater driver fault (rare)
Contamination or physical damage to the sensor

Malfunction Indicator Lamp (MIL) illuminated
Possible reduced NOx control performance or emission-related limp mode depending on vehicle
Diagnostic trouble code P23BB stored (Bank 1 Sensor 3 heater resistance)
No direct change in drivability in many cases, but emissions test may fail

Read and record freeze frame and live data with a scan tool; confirm active/inactive status of DTC
Perform a visual inspection of the NOx sensor, connector, and wiring on Bank 1 Sensor 3 for damage, corrosion, or contamination
With ignition off, disconnect sensor and measure heater element resistance at the sensor terminals
Check continuity and resistance of heater circuit from sensor connector to PCM connector
Verify heater supply voltage and ground at the connector with ignition on and (if safe) while heater is commanded on
Inspect related fuses and relays feeding the heater circuit

Typical heater resistance: generally low (typical range ~2–30 ohms depending on sensor design); consult OEM spec for exact value
Heater supply voltage: battery voltage (approx. 11–14 V) when commanded on; some systems use PWM switching from PCM
Heater current: can be from ~0.5 A up to several amps depending on resistance and system
Expected behavior: resistance stable and within spec; when commanded on, supply shows voltage/current and PCM ground switches or PWM pulses

Confirm code and gather context: read all codes, freeze frame, and relevant live data (NOx sensors, heater status).
Visual inspection: check sensor body, connector, and wiring on Bank 1 Sensor 3 for heat damage, corrosion, or physical damage.
Measure heater resistance at the sensor: with ignition off and sensor disconnected, measure ohms across the heater terminals. Compare to OEM spec. A very high/OL reading indicates open/heater failure; a much lower value than spec could indicate short.
Check wiring and connectors: verify continuity and resistance from sensor connector to PCM connector; check for shorts to ground or battery. Repair any damaged wiring or corroded terminals.
Verify supply and ground under command: with scan tool, command the heater on (if possible) and measure supply voltage at the sensor and monitor PCM driver (ground or PWM). Check for expected voltage/pulsing and current draw. Use proper clamps/meters rated for current if measuring amperage.
Inspect fuses/relays: verify fuses and relays in the heater supply circuit are intact and supplying power.
Repair or replace as indicated: replace sensor if heater element fails or wiring/connector if damaged. Secure and protect repaired wiring from heat/abrasion.
Clear codes and test: after repair, clear DTCs, perform required relearn procedures if any, and road test to confirm code does not return and live data is normal.