P2A39 code meaning
O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 3
Powertrain system Generic code P2Axx codes Check engine light
What P2A39 means
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.
P2A39 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P2A39
- Check engine light after repeated detection
- Sensor 3 reading implausible or missing in live data
Common causes of P2A39
- Most likelyPump-current wire chafed through to body or exhaust bracket
- PossibleInternal short in the probe after thermal shock or water ingress
- Less likelyFaulty sensor interface in the engine control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor b1s3Wiring harnessECM
What each part of P2A39 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| A | Area: hybrid propulsion. |
| 39 | The exact fault in that area. |
What to do next
- Note P2A39 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2A39
What does P2A39 mean?
P2A39 means "O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 3". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P2A39?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2A39 fail an emissions test?
Yes, it can. P2A39 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2A39 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2A39 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.