Powertrain, generic (extended)

P2AF0 Intake Air O2 Sensor Negative Current Control Circuit Low Bank 2

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2AF0 is stored when the negative current control circuit of the bank 2 intake oxygen sensor falls below its window. Because the return is meant to sit at a bias of roughly 2.5 V, which Saab's 2010 9-5 lists as the test value on terminal 2 of its exhaust probe, any path to chassis ground pulls it down: insulation worn through at a clip, a crushed connector or an internal short in the sensor. Ford assigns a grounded VM lead on bank 2 exhaust probes to P0151. No manufacturer publishes P2AF0, so the description rests on CARB's range checks and the Bosch pinout. When bank 1 shows P2AE7 as well, suspect a shared harness section first. With the bias gone, the oxygen value of bank 2 is unusable and EGR is cut back. P2AEF is open, P2AF1 high, P2AED the low fault on the pump lead.

Likely causes

Return lead worn through at a clip or bracket
Crushed or damaged sensor connector
Internal short of the sensor to ground

Symptoms

  • Check engine light on
  • EGR on bank 2 cut back, possibly higher NOx

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–350
Time0.3–2 h

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

Parts involved

intake air o2 sensor b2wiring harnessecm

Related codes

P2AEFP2AF1P2AEDP2AE7P2255

References: saabwisonline.com, newtonnet.co.uk, bosch-motorsport.com, law.cornell.edu.