P2A39O2 Sensor Positive 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
- P2A39 is set when the pump-current lead feeding the rearmost wide-band probe on bank 1 (sensor 3) is pulled below its permitted window, typically because the wire rubs through to chassis ground near the hot rear exhaust section. At ignition-on Saab's 2010 9-5 shows roughly 2.8 V on the pump-current pins of its front probe, so a reading near zero points to a ground short. No manufacturer publishes P2A39 itself; Ford stores a short to ground on the IP wire of its front probes under P0131, and CARB only requires that such out-of-range signals be caught. P2A38 covers the open line, P2A3A the high side, P22AC the sensor 2 case. Apart from the warning lamp, the aftertreatment monitors using this probe stay incomplete.
- What you may notice
- Check engine light after repeated detection
- Sensor 3 reading implausible or missing in live data
- Likely causes
- LikelyPump-current wire chafed through to body or exhaust bracket
- PossibleInternal short in the probe after thermal shock or water ingress
- RareFaulty sensor interface in the engine control module
- 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.