What it means
The positive-current control circuit for the oxygen sensor at Bank 1 Sensor 1 is below its expected range. The code identifies a circuit condition, not a confirmed failed sensor.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 1 is the upstream wide-band oxygen sensor used by the engine control module to adjust fueling from exhaust oxygen measurements. P2238 means the sensor’s positive pumping-current control circuit is reading below its expected range, which can result from a short to ground, a degraded sensor, or poor contact.
Common causes
Most likely first.
- Pump line shorted to ground
- Wide-band sensor aged
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Check freeze-frame and live data for Bank 1 Sensor 1 to note when the low-circuit fault occurs and whether it is persistent.
- Inspect the upstream Bank 1 Sensor 1 connector and harness for corrosion, moisture, pin damage, or wiring rubbed against the exhaust.
- Check for an exhaust leak near the sensor that could produce readings inconsistent with other engine data.
- With the wiring diagram, test the positive pumping-current circuit for a short to ground and inspect connector contact quality.
- If the circuit is intact, test Bank 1 Sensor 1 and its heater and reference circuits according to the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose Bank 1 Sensor 1 connector contacts where appropriate.
- Repair a positive pumping-current wire shorted to ground or damaged insulation.
- Repair an exhaust leak near Bank 1 Sensor 1.
- Replace the upstream wide-band sensor if testing confirms it is aged or internally faulty.
Can I keep driving?
A short, gentle drive may be possible if the engine runs smoothly, but avoid extended trips and heavy acceleration. The module may use less accurate fuel control, increasing fuel use and emissions; stop driving if it begins to misfire or run roughly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.