P2198: O2 Sensor Signal Biased/Stuck Rich (Bank 2, Sensor 1)
Key takeaways
- P2198 means the upstream oxygen sensor on bank 2 keeps reporting a rich mixture even after the computer has cut fuel as far as it's allowed.
- Bank 2 only exists on V6, V8 and flat engines; it's the side without cylinder 1.
- It's usually safe to drive, but a fuel smell, black smoke or a flashing light means the engine may really be rich and needs a look soon.
- Either the sensor is lying (aged, contaminated, or a wiring short) or it's telling the truth about a leaking injector or high fuel pressure, so check before buying a $150–$400 sensor.
- Ford has bulletins naming P2198 on the 2018–2020 F-150 2.7L EcoBoost and 2015–2018 Transit.
What P2198 means
The front oxygen sensor on bank 2 keeps saying “rich,” and the engine computer can’t make it change its mind. Scanners call it O2 Sensor Signal Biased/Stuck Rich (Bank 2, Sensor 1). The computer uses this sensor to trim fuel on bank 2. When the sensor keeps reporting rich while the computer has already cut fuel to its limit, or while the reading doesn’t match what the other sensors show, the computer decides the signal is stuck or biased and sets P2198.
Bank 2 is the side of a V6, V8 or flat engine without cylinder 1; four-cylinder engines don’t have one. Sensor 1 is upstream, before the catalytic converter. On many newer engines it’s a wide-band air-fuel sensor, and the code works the same way.
Is it safe to drive?
Yes, in most cases. If the sensor is lying, the computer may run bank 2 slightly lean or fall back to a default mixture. You may lose a little fuel economy, and the car will fail an OBD emissions inspection with the light on.
What changes the answer: a strong fuel smell, black smoke, a rough idle or a flashing check engine light. Those mean the engine may really be running rich or misfiring, and unburned fuel can overheat the catalytic converter. Get that checked before driving much further.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Aged or contaminated sensor (coolant, oil, silicone, fuel) | Signal stuck rich while fuel trims are already strongly negative and bank 1 looks normal; coated or sooty tip | $150–$400 |
| Engine really running rich on bank 2 (leaking injector) | Fuel smell, injector leak-down or balance test; misfire codes on that bank | $250–$600 per injector |
| Something rich on both banks (purge valve stuck open, high fuel pressure) | P2196 or P0175 set too; trims improve with the purge line pinched; pressure gauge above spec | $120–$350 purge valve; $150–$450 regulator |
| Signal wire shorted to heater or power wire, water in the connector | Melted harness near the exhaust, corrosion in the plug; signal stays high with the sensor unplugged | $100–$250 |
| Engine computer software (some makes) | A bulletin for your exact model and year names P2198 | $100–$200, often $0 under warranty |
Wide-band sensors, trucks, and sensors rusted into the pipe land at the top of these ranges.
What to check first
- Read every stored code. P2198 alone on a high-mileage engine usually means the sensor. With P2196 on bank 1 as well, look for a shared cause like fuel pressure or the purge valve. With misfire codes on bank 2, suspect an injector.
- Look for a bulletin before buying parts.
- Inspect the harness and connector from the sensor back, for wires resting on the exhaust, melted insulation, or water and green corrosion in the plug.
- Compare both banks in live data on a warm engine. If bank 2 trims are strongly negative and the sensor still reads rich, the sensor is suspect; if a leak-down test shows fuel dripping, it’s the injector.
- Replace the sensor last, then clear the code and drive a normal mixed trip to confirm. Our O2 sensor guide explains what a shop looks for.
The bulletins are Ford and Land Rover. Ford lists P2198 with P2196 on some 2018–2020 F-150s with the 2.7L EcoBoost, where engineering was still working on a fix when the bulletin was issued, and among drivability codes on 2015–2018 Transit vans built on or before July 24, 2018. Land Rover covers heated oxygen sensor codes on the 2016 Range Rover.
What it costs
The cheap outcome is a wiring or connector repair at $100–$250, or a software update, often free under warranty. The common outcome is a new upstream sensor at $150–$400. The expensive outcome is a real rich condition: a leaking injector at $250–$600 each, or a purge valve or fuel pressure regulator. A $100–$180 diagnosis that compares both banks keeps you from buying a sensor that was telling the truth.
Related codes
P2198 often appears with P0175 (bank 2 rich) or P2196 (same fault, bank 1). P2197 is the opposite, stuck lean on bank 2. If the heater code P0155 or the slow-response code P0153 shows for the same sensor, the sensor itself becomes more likely. 5 complaints filed with NHTSA mention P2198; those are owner reports, not confirmed causes.
What owners report to NHTSA
5 complaints filed with NHTSA mention P2198, 4 of them since 2015, across 5 different models. The component owners most often filed it under: engine.
Manufacturer service bulletins that name P2198
12 technical service bulletins and manufacturer communications filed with NHTSA mention P2198, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- FORD F-150 (2018, 2019, 2020), bulletin 10176003: Some 2018-2020 Model Year F-150 vehicles equipped with a 2.7L EcoBoost engine may experience an illuminated malfunction indicator lamp (MIL) with DTC P2196 and/or P2198 stored in the powertrain control module (PCM). Engi…
- FORD TRANSIT (2015, 2016, 2017, 2018), bulletin 10148711: Some 2015-2018 Transit vehicles built on or before 24-Jul-2018 may exhibit various drivability concerns including difficulty starting, misfires and/or an illuminated MIL with diagnostic trouble codes (DTCs) P00BD, P1247,…
- LAND ROVER RANGE ROVER (2016), bulletin 10105881: "ISSUE: THE CUSTOMER MAY OBSERVE A MIL IN THE INSTRUMENT CLUSTER RELATING TO THE ENGINE SYSTEM (CHECK ENGINE LIGHT) AND ONE OR MORE CODES STORED IN THE PCM RELATING TO HEATED OXYGEN SENSOR (HO2S) IN THE EXHAUST SYSTEM. T…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with P2198?
Usually yes. If the sensor is at fault, the engine may run a little lean or feel normal, and fuel economy can drop. If the engine is really running rich, you may smell fuel or see black smoke; that can overheat the catalytic converter, so get it checked soon.
Where is bank 2 sensor 1?
Bank 2 is the side of a V or flat engine that doesn't have cylinder 1. Sensor 1 is the upstream sensor, in the exhaust manifold or the pipe right after it, ahead of the catalytic converter.
Will a new O2 sensor fix P2198?
Often, when the old sensor is original and high-mileage. But if the engine is really rich, or the signal wire is shorted, a new sensor sets the same code. A shop should compare both banks and check fuel trims first.
What's the difference between P2196 and P2198?
Same fault, different side. P2196 is the upstream sensor on bank 1, P2198 on bank 2. If both are set, look for something both banks share, like fuel pressure or the EVAP purge valve, before replacing two sensors.