P2A3CO2 Sensor Negative Current Control Circuit Low Bank 1 Sensor 3
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2A3C is stored when the virtual-ground return belonging to the third probe of bank 1 falls below its intended bias. Because this line normally floats around 2.5 V rather than at chassis potential, a chafed wire touching the body or an exhaust bracket drags it down and leaves the pump cell little room to reverse its current, so rich mixtures can hardly be measured. No manufacturer publishes P2A3C; this text relies on CARB's demand to detect out-of-range sensor circuits, on the Bosch LSU 4.9 pin layout and on the bias value Saab gives for its 2010 9-5 at the plug. P2A3B is the open return, P2A3D the high case, P2A39 the matching low fault on the pump lead. The lamp is lit and the downstream sensor checks will not complete.
- What you may notice
- Check engine light after repeated detection
- Downstream emission monitors stay incomplete
- Likely causes
- LikelyVirtual-ground wire chafed through to chassis ground
- PossibleInternal short from the common electrode to the sensor housing
- RareBias stage in the engine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.