P2198: O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 1
What to do
Expect hesitation and a flat spot, because the engine is being starved of fuel by a sensor wrongly claiming excess. Avoid heavy load until repaired. If both banks are reporting stuck sensors at once, say so — two sensors rarely fail together, and the shared supply or ground that feeds both is a much more likely and much cheaper explanation than a pair of new sensors.
What this code means
The stuck-rich condition described at P2196, on the upstream sensor of the second cylinder bank. The engine ends up running lean as a result, and the bank-swap test set out at P2197 applies here too and is the fastest way to settle whether the sensor is at fault.
Where both banks report a stuck sensor at the same time, stop treating them as two sensor faults. Two upstream sensors do not fail simultaneously often enough to be the likely explanation, and the alternatives are all shared: the reference or ground they have in common, the module input stage reading both, or a supply problem of the kind set out at P0641 and P0882. That is the argument the corpus makes more often than any other — one shared thing failing looks exactly like many separate things failing — and here it is protecting the owner from paying for two expensive sensors that were never faulty.
Likely causes
Start here
- Faulty oxygen sensor · moderate
- Signal wire shorted to the heater circuit · moderate
Less common
- Contaminated oxygen sensor element · moderate
- Failed sensor reference voltage supply · moderate
- Leaking fuel injector · moderate
- Poor module ground connection · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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