OBD NOx Sensor Performance - Slow Response Low to High Bank 1 Sensor 3
What it means
P23BF stands for NOx Sensor Performance - Slow Response Low to High Bank 1 Sensor 3. P23BF is a P code, so the fault sits in the engine, transmission and emissions systems. For P23BF, the second digit places it in ignition and misfire. For P23BF, work through the cause list below, cheapest checks first.
Where it lives
For P23BF, the description names the sensor as the part involved. The description of P23BF puts it on bank 1.
What to check first
For P23BF, compare the reading on bank 1 against the other bank on the same scan tool, because a bank that reads differently from its twin is the fault.
Check these first
- P23BF: Failing ignition coil, spark plug, or spark plug wire
- P23BF: Faulty crankshaft or camshaft position sensor
- P23BF: Wiring or connector damage in the ignition circuit
- P23BF: Low compression or engine mechanical wear
- P23BF: Incorrect ignition timing or a stretched timing chain
What to do next
P23BF reports from the ignition and misfire system. These steps cover P23BF in general, and the exact cause on your vehicle can differ from the cause named above.
- P23BF: Read misfire counts and freeze frame data with an OBD-II scanner
- P23BF: Test spark output and inspect spark plugs and coils
- P23BF: Check crankshaft and camshaft position sensor signals while cranking
- P23BF: Swap suspect ignition parts between cylinders to see if the fault moves
- P23BF: Compression test if the issue persists on the same cylinder
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.