OBDII Code List

P2198 MERCURY - Oxygen Sensor Signal Biased/Stuck Rich Bank 2 Sensor 1

Repair Importance Level: 2/3
Repair Difficulty Level: 2/3   
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Possible causes

  • Faulty Front Heated Oxygen Sensor Bank 2
  • Front Heated Oxygen Sensor Bank 2 harness is open or shorted
  • Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
  • Inappropriate fuel pressure
  • Faulty fuel injectors
  • Intake air leaks may be faulty
  • Vacuums leaks

Tech notes

There is a factory service bulletin for the following Mercury models:
2010-2011 Mercury Milan
2009-2011 Mercury Mariner
Mercury Factory Service Bulletin OBDII Code P2198

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Excessive Fuel Consumption

P2198 Mercury Description

The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. A heated oxygen sensor (HO2S) indicating rich at the end of a test is trying to correct for an over-lean condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.
OBDII Code P2198 Mercury - Oxygen Sensor Signal Biased/Stuck Rich Bank 2 Sensor 1 -

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