These are code references, not a list of confirmed faults on every vehicle. Read the source and applicability notes, then match the exact vehicle, year, engine and scan report.

O2 Sensor Reference Voltage Circuit High Bank 2 Sensor 1

Front oxygen reference-ground circuit fails its open-circuit check

Diesel air-fuel sensor negative-current circuit low

Air-fuel sensor negative-current circuit high input

The bank 2 negative-current circuit check changes with sensor operating state

O2 Sensor Negative Current Control Circuit Low Bank 2 Sensor 1

O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1

secondary-air relay low circuit can include an open connection

secondary-air relay high circuit is separate from pump-flow performance

AIR System Control B Circuit Low

Ford NOx sensor 1 calibration memory fails its CRC check

Ford NOx sensor 2 calibration-memory integrity fault

NOx Sensor Performance - Signal Biased/Stuck High Bank 1 Sensor 1

NOx Sensor Performance - Signal Biased/Stuck Low Bank 1 Sensor 1

NOx Sensor Performance - Signal Biased/Stuck High Bank 1 Sensor 2

NOx Sensor Performance - Signal Biased/Stuck Low Bank 1 Sensor 2

AIR System Control B Circuit High

Turbo bypass valve fails the coast-down pulsation check

Ford 6.0L boost pressure is absent under qualifying demand

Boost-system performance uses an accumulated underboost deviation

Water in Fuel Sensor A Circuit

Water in Fuel Sensor A Circuit Range/Performance

Water in Fuel Sensor A Circuit Low

Water in Fuel Sensor A Circuit High

Water in Fuel Sensor A Circuit Intermittent

Fuel conductivity is outside the sensor’s normal fuel range

Water in Fuel Lamp Control Circuit

Turbocharger/Supercharger A Boost Pressure Too High - Mechanical

Turbo response monitoring needs the correct engine-specific test

low DPF flow resistance can also implicate pressure-sensing pipes

Bank2 GPF deterioration monitoring depends on pressure normalization

Turbocharger Boost Control B Slow Response

Rear oxygen sensor fails to respond to commanded enrichment

Rear oxygen sensor remains rich during the fuel-cutoff test

A lean-biased rear-sensor code with an unresolved bank label in the source

Interpreting a rear-sensor rich-bias check when the table wording conflicts

Volkswagen sensor-three signal stuck lean

Volkswagen sensor-three stuck-rich response check

O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 3

O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 3

O2 Sensor Signals Swapped Bank 1 Sensor 3/Bank 2 Sensor 3

intake leakage includes the PCV system and runner-position evidence

Barometric Pressure Sensor C Circuit

the documented BARO C code tests turbo-inlet pressure agreement

BARO sensor C reports pressure below its allowed range

BARO sensor C reports pressure above its calibrated ceiling

BARO C has excessive accumulated signal movement

Air Flow Restriction/Air Leak Between Air Filter and MAF Bank 2

Ram air-cleaner-to-MAF fault and a two-trip monitor update

Ram intake-leak indication and verifying a successful flash

An inferred intake leak needs a nearly closed throttle and healthy inputs

Injector Control Pressure Sensor Circuit

Ford 6.0L ICP feedback exceeds commanded pressure

Ford 6.0L ICP sensor voltage is below range

Ford 6.0L ICP sensor voltage exceeds its range

Injector Control Pressure Sensor Circuit Intermittent

Ford 6.0L running injection-control pressure is too high

Ford 6.0L ICP remains too high with the engine off

rail pressure remains low after metering control reaches its limit

rail pressure stays low despite maximum regulator command

High-pressure fuel delivery falls below the requested target

Fuel rail pressure stays above the requested target

A low learning-limit fault is about fuel-pressure adaptation

An upper adaptation boundary is not the same as rail overpressure

Ford 6.0L actual ICP falls below commanded pressure

Cranking rail pressure remains below the starting monitor boundary

Injector Control Pressure Erratic

regulator-controlled rail pressure exceeds a speed-dependent ceiling

regulator 2 open circuit is diagnosed with the driver off

regulator 2 low circuit is an off-state ground-short test

fuel pressure regulator 2 driver short-to-power detection

oxygen concentration drift during stable deceleration

An out-of-range wideband signal with operating conditions that need careful reading

Journey pedal-signal incompatibility and the 2.4 L calibration row

Fuel Pressure Regulator B Exceeded Control Limits - Pressure Too Low

Fuel Pressure Regulator B Exceeded Control Limits - Pressure Too High

Fuel Pressure Regulator B Exceeded Learning Limits - Too Low

Fuel Pressure Regulator B Exceeded Learning Limits - Too High

Tailpipe NOx processor and circuit faults share this code in Ford’s summary

post-catalyst NOx sensor current-control instability