SPN 3256, FMI 5 - EGO3 Open/Lazy (HO2S3

SPN 108, FMI 1 - BP Low Pressure

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SPN 3217, FMI 5 - EGO1 Open/Lazy (HO2S1)

PK/BK

• Heated or Universal Exhaust Gas Oxygen Sensor (Bank 1-Sensor 1/Before Catalyst) • Check Condition- Engine Running • Fault Condition- HEGO/HO2S or UEGO cold longer than the time defined in the calibration • Corrective Action(s)- Illuminate MIL and/or sound audible warning or illuminate secondary warning lamp, disable adaptive learn fueling correction for key-cycle, and disable closed-loop fueling correction during active fault. • Emissions related fault

The HEGO/HO2S sensor is a switching-type sensor about stoichiometry that measures the oxygen content present in the exhaust to determine if the fuel flow to the engine is correct. A UEGO sensor measures the exhaust content across a wide-range of air-fuel ratios with a linear analog output proportional to lambda/equivalence ratio/air-fuel ratio. In either case, if there is a deviation between the expected reading and the actual reading, fuel flow is precisely adjusted using the Closed Loop multiplier and then “learned” with the Adaptive multiplier. The multipliers only update when the system is in either “CL Active” or “CL + Adapt” control modes.

This fault will set if the sensor element is cold, non-responsive, or inactive for x seconds as defined in the diagnostic calibration. Cold, non-responsive, or inactive are determined based on two criteria 1) a measurement of the feedback sense element (zirconia) to determine its temperature or 2) a lack of change in sensor feedback. This fault should disable closed-loop when it is active and adaptive learn for the key-cycle.

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