Fix P2198: Mechanic’s solutions that WORKED

The P2198: Oxygen Sensor Signal Biased/Stuck Rich (Bank 2 Sensor 1) points out a fault in the oxygen sensor, indicating that it’s detecting a richer-than-normal fuel-air mixture. This can be due to various reasons, including sensor issues, vacuum leaks, or fuel system problems. Timely diagnosis and repair are important to maintain engine efficiency and prevent further complications.

P2198 quick overview

Meaning	P2198: Oxygen Sensor Signal Biased/Stuck Rich (Bank 2 Sensor 1)
Is it serious?	P2198 can indicate a significant issue affecting engine performance and emissions, and should be addressed promptly to prevent potential damage.
Possible causes	– Oxygen sensor failure or malfunction – Vacuum leaks in the intake manifold or hoses – Faulty or dirty Mass Air Flow (MAF) sensor – Exhaust leaks before the sensor – Fuel pressure too high or leaking fuel injectors – Malfunctioning Engine Control Module (ECM)
How to diagnose?	Inspect Oxygen Sensor: Check the condition and operation of the Bank 2 Sensor 1 oxygen sensor. Check for Vacuum Leaks: Search for leaks in the intake system, including manifold and hoses. Evaluate MAF Sensor: Assess the Mass Air Flow sensor for cleanliness and proper functioning. Examine Exhaust System: Look for leaks in the exhaust system, especially before the O2 sensor. Assess Fuel Pressure: Verify if the fuel pressure is within the specified range. Inspect Fuel Injectors: Check for leaking or malfunctioning fuel injectors. Check ECM: Evaluate the Engine Control Module for any signs of malfunction.

How to fix P2198 – learn from mechanics

I looked into P2198 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle Information: 2003 Ford Ranger Edge 4.0L

Issue + Repair History:

• Engine has rough idle.
• Code P2198 repeatedly appearing.
• Replaced engine due to previous issues (spun bearing, piston damage).
• Replaced O2 sensors, intake, plugs, wires, hoses.
• Fuel pressure at 62 psi, no vacuum leaks detected.

Other OBD2 Codes + Test Results:

• P2198: B2S1 oxygen sensor rich.

Suggestions to Fix Issue:

• Check mass airflow sensor operation.
• Perform a cylinder balance test.
• Verify timing chain positioning.
• Inspect fuel trims at various engine speeds.
• Confirm correct connection of O2 sensors.
• Examine fuel pressure regulator and vacuum lines.
• Investigate possible wiring issues, including PCM and harness.
• Check PCM ground wire.
• Assess fuel return line and fuel pressure regulator.
• Analyze coolant presence in B2S1 O2 connector.
• Inspect replaced oxygen sensor for compatibility (Ford, federal, or California).
• Examine injector spray pattern, spark plugs, compression, and MAF sensor.

Final Fix:

• Discovered from customer that the issue was present with the original engine.
• Identified that fuel pressure did not maintain after turning off the key.
• Found cylinder #6 full of fuel due to a leaking injector.
• Replaced the faulty injector with an OEM part, resolving the issue.

Case #2: Ford

Vehicle Information: 2011 Ford E-350 Super Duty 5.4L

Issue + Repair History:

• Experiencing code P2198 (2/1 stuck rich) regularly and P2196 (1/1) intermittently.
• Fuel trim at around 25% ST on acceleration, -28% ST on deceleration, and +/- 7% ST at idle.
• Downstream HO2S both read 0.98 VDC on deceleration.
• MAF reading seems normal but suspected to be faulty.
• No change in readings with disconnected purge valve and crankcase hose.
• Fuel pressure consistently at 60 psi but drops on KOEO.
• Replaced B2S1 A/F sensor with OE unit and updated PCM.
• Inspected left bank injectors for leaks; none found.
• Intermittent rough start-up and fluctuating idle.

Other OBD2 Codes + Test Results:

• P2198: B2S1 stuck rich.
• P2196: B1S1 stuck rich.

Suggestions to Fix Issue:

• Follow the fault code diagnosis tree in repair manuals.
• Check for fuel in the oil and inspect the PCV system.
• Assess the MAF sensor readings against standard values.
• Consider the possibility of bad MAF sensor.
• Check and reset the fuel composition PID for incorrect E85 readings.
• Inspect the purge valve and MAF sensor cleanliness.

Final Fix:

• Replaced the MAF sensor based on similarities to a known VW MAF failure.
• Fuel trims and data normalized after replacement.
• Checked alcohol content, found to be normal.
• Vehicle operational without issues for several days post-repair.

Case #3: BMW

Vehicle Information: 2010 BMW 528i 3.0L

Issue + Repair History:

• Initial issue: Check engine light due to B1S1 O2 sensor malfunction. Replaced sensor.
• New issue: MIL lamp on with lean run codes (P2096, P2207, P2196, P2198).
• Replaced remaining 3 O2 sensors due to high mileage.
• Found and repaired valve cover leak.
• P2096 code persists despite no detected leaks.
• Observed discrepancy in smooth run values between banks 1 and 2.
• Adaptations at idle are within normal range.
• Planning to replace plugs and recheck valve cover bolts.

Other OBD2 Codes + Test Results:

• P2096: Post catalyst fuel trim system too lean.
• P2196: O2 sensor signal biased/stuck rich (Bank 1 Sensor 1).
• P2207: No data provided.
• P2198: O2 sensor signal biased/stuck rich (Bank 2 Sensor 1).

Suggestions to Fix Issue:

• Check for a clogged catalytic converter via back pressure test.
• Consider the possibility of an oil separator issue.
• Assess fuel trims at various engine conditions and analyze pre and post AFS/O2 sensor readings.
• Examine freeze-frame data to determine conditions under which P2096 sets.
• Under load, look at multiplicative fuel adaptations and exhaust back pressures.
• Under idle, check crankcase vacuum.
• Inspect for clogged injectors.

Final Fix:

• After replacing O2 sensors, plugs, and valve cover, only P2096 code remains.
• Suspected need for a new catalytic converter due to high mileage (171k).
• Customer opted to try using Sea Foam treatment before considering catalytic converter replacement.

Case #4: Toyota

Vehicle Information: 2003 Toyota Camry LE 3.0L

Issue + Repair History:

• MIL light on with slight surge from 20 to 40 mph.
• Initial code: B1S1 lean.
• Cleaned mass air flow sensor and swapped bank 1 and 2 AF sensors.
• New code: P0174 for Bank 2 lean.
• Installed a new AF sensor in Bank 1, returned the original Bank 1 sensor to Bank 2.
• Fuel trim values around 1% after repair.
• Customer returned with code P2198 (B2S1 stuck rich) but no further issues during a 20-mile test drive.
• Consideration of potential computer issues.

Computer Codes & Descriptions:

• P2195: Bank 1 Sensor 1 stuck lean.
• P0174: Fuel trim lean Bank 2.
• P2198: Bank 2 Sensor 1 stuck rich.

Suggestions to Fix Issue:

• Check if the neutral sensor voltage aligns with expected values (around 2.5 to 3 volts).
• Analyze both short-term and long-term fuel trims.
• Consider the possibility of computer problems, which are known in these Camry models.
• Investigate related recalls or warranty issues, especially for ECM replacement.

Final Fix:

• Replacing the fuel sensor resolved the issue.
• The car has been running without the check engine light for a month.

Case #5: Ford

Vehicle Information: 2014 Ford E-250 5.4L

Issue + Repair History:

• Initial issue: Check engine light for bank 1 sensor 1 O2, misfires.
• Developed power and dying issues.
• Replaced both front O2 sensors, performed BG injector service.
• Replaced spark plugs, coil boots, and catalytic converters (which were badly clogged).
• Conducted smoke test: no vacuum leaks found.
• Fuel pressure steady at 55 psi.
• Tried new mass airflow sensor: no change.
• Cylinder balance test shows all cylinders miss a bit, but no specific cylinder stands out.
• Codes P2196, P2198, P2271, P2273 appeared after new cats installed.
• No fuel filter on rail, air filter new.

Computer Codes & Descriptions:

• P2196: O2 sensor signal biased/stuck rich.
• P2198: O2 sensor signal biased/stuck rich.
• P2271: O2 sensor signal biased/stuck rich.
• P2273: O2 sensor signal biased/stuck rich.

Suggestions to Fix Issue:

• Reset Keep Alive Memory (KAM) after repairs and re-evaluate.
• Disconnect and inspect EVAP purge valve and check carbon canister for raw fuel.
• Consider potential issues with new MAF sensor and its calibration.
• Investigate possibility of a leaky fuel injector, especially if experiencing extended crank.
• If flex fuel system, check alcohol percentage on scan tool and consider KAM reset.
• Verify proper connection of O2 sensors to prevent confusion in the PCM.

Final Fix:

• Identified and repaired a faulty vent valve on top of the engine.

Advice	Brief Description of Diagnostic Step
Reset KAM (Keep Alive Memory)	This involves resetting the vehicle’s onboard computer system to clear old data, potentially resolving sensor-related discrepancies.
Check and Replace O2 Sensors	Inspect and, if necessary, replace oxygen sensors as they might be providing incorrect readings leading to the P2198 code.
Inspect and Test MAF Sensor	Evaluate the mass airflow sensor for proper operation as it can affect fuel mixture and trigger rich condition codes.
Perform Smoke Test for Vacuum Leaks	Conduct a smoke test to identify any vacuum leaks in the system, which can lead to incorrect air-fuel mixture and sensor readings.
Check Fuel System Components	Inspect components such as fuel injectors, fuel pressure, and fuel trims, as issues here can lead to rich condition faults like P2198.
Inspect and Repair Exhaust System	Check the exhaust system, including the catalytic converter, for blockages or issues that might affect sensor readings.