P2AC4 Intake Air O2 Sensor Reference Voltage Circuit Range/Performance Bank 2

P2AC4 marks an implausible but electrically intact reference voltage on the second-bank intake oxygen sensor. It is the bank 2 twin of P2AC0, which Stellantis documents for the four-cylinder Alfa Romeo 2.0L; an inline four with one intake path has no bank 2, so P2AC4 would only appear on engines fitted with a second intake sensor. No manufacturer documents this code publicly. A plausibility test of this kind typically compares the sensor reading with what EGR valve position, intake pressure and air mass lead the ECM to expect; Ford's patents show that pressure changes and humidity shift the output and must be compensated. Ageing, contamination from crankcase vapours or an overly strict calibration are therefore likelier causes than a broken wire. P2AC3 is the open circuit.

Likely causes

Symptoms

• Check engine light on
• Usually no noticeable change in driveability

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: patents.google.com, static.nhtsa.gov, law.cornell.edu.