What it means
The trim adjustment for the pumping current of the intake air oxygen sensor on bank 1 reports a circuit low condition. Wide-band lambda regulation on the intake side is impaired.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 intake air oxygen sensor uses a wide-band pump cell, and the module monitors the trim circuit that adjusts its pumping current. This code sets when that circuit's signal is too low, which can result from a short to ground, an internally shorted pump cell, or a poor terminal connection.
Common causes
Most likely first.
- Pump current wire shorted to ground
- Internal short in pump cell
- 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
- Record freeze-frame data and check live bank 1 intake oxygen-sensor values for a low or unresponsive pump-current trim signal.
- Inspect the bank 1 sensor connector and harness for corrosion, damaged insulation, loose terminals, or wiring contacting ground.
- Check that connector pins are seated and clean, then see whether the signal changes when the connection is secured.
- Using the wiring diagram, test the pump-current trim circuit for a short to ground and check continuity through its connectors.
- If the wiring and connections pass, test the bank 1 sensor pump cell against the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose bank 1 sensor terminals.
- Repair wiring shorted to ground or damaged insulation in the pump-current trim circuit.
- Replace the bank 1 intake air oxygen sensor if its pump cell is internally shorted.
- Clear the code and confirm the trim signal and sensor operation.
Can I keep driving?
You can often drive a short distance if the engine runs normally, but unreliable bank 1 oxygen feedback can increase fuel use and emissions. Avoid prolonged driving if hesitation or rough idle develops, and fix the circuit before an emissions test.
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.