OBD O2 Sensor Exhaust Sample Error Bank 1 Sensor 2
What it means
P237A stands for O2 Sensor Exhaust Sample Error Bank 1 Sensor 2. P237A is a P code, so the fault sits in the engine, transmission and emissions systems. For P237A, the second digit places it in ignition and misfire. For P237A, work through the cause list below, cheapest checks first.
Where it lives
For P237A, start at the sensor the description names. The description of P237A puts it on bank 1.
What to check first
For P237A, 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
- P237A: Failing ignition coil, spark plug, or spark plug wire
- P237A: Faulty crankshaft or camshaft position sensor
- P237A: Wiring or connector damage in the ignition circuit
- P237A: Low compression or engine mechanical wear
- P237A: Incorrect ignition timing or a stretched timing chain
What to do next
P237A belongs to the ignition and misfire system. These are the general steps for P237A, and the exact cause on your vehicle can differ.
- P237A: Read misfire counts and freeze frame data with an OBD-II scanner
- P237A: Test spark output and inspect spark plugs and coils
- P237A: Check crankshaft and camshaft position sensor signals while cranking
- P237A: Swap suspect ignition parts between cylinders to see if the fault moves
- P237A: Compression test if the issue persists on the same cylinder
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.