Powertrain, generic (extended)

P2AC0 Intake Air O2 Sensor Reference Voltage Circuit Range/Performance Bank 1

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P2AC0 is set when the reference voltage circuit of the bank 1 intake air oxygen sensor is electrically present but behaves implausibly, for example drifting or not matching what the ECM expects for the current EGR and pressure state. Stellantis documents it explicitly for the 2.0L turbo four (sales code EC2) of the Alfa Romeo Giulia and Stelvio: TSB 18-067-22 REV. B for 2022 Giulia and TSB 18-041-23 REV. A for 2022 Stelvio both cure a lit MIL with P2AC0 by flashing new engine software, so a false detection rather than a worn part. The 2017 Giulia bulletin 18-030-17 already listed it next to P2B89. Ford's intake oxygen patents show that intake pressure and humidity shift the sensor output, which any plausibility check has to allow for. P2ABF is the open circuit, P2AC4 bank 2.

Likely causes

Engine software that detects the fault falsely (Stellantis reflash for Giulia/Stelvio 2.0L)

Intake oxygen sensor aged or contaminated by oil mist from crankcase ventilation

High resistance in the reference wire or connector

Symptoms

Check engine light on
Usually no noticeable change in driveability

Repair estimate

DifficultyEasyWorkshop job

Parts and labour€0–350

Time0.2–1.5 h

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

Parts involved

intake air o2 sensor b1wiring harnessecm

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, patents.google.com.