What it means
The Vs negative line on bank 1, sensor 1 reads above the upper threshold. Often a short to positive or a damaged ECU sensor amplifier.
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, and its Vs− negative-current line is part of the reference circuit used to measure the exhaust air-fuel mixture. The control module sets this code when the Vs− signal is higher than expected, which can point to a short to positive, an internal sensor fault, or a poor connection.
Common causes
Most likely first.
- Vs negative line shorted to positive
- Internal short in sensor
- 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 data and related fuel-trim or oxygen-sensor codes to identify when Bank 1 Sensor 1’s Vs− signal went high.
- Inspect the upstream Bank 1 Sensor 1 connector and harness for corrosion, damaged insulation, pinching, or contact with a power wire.
- Use the wiring diagram to identify the Vs− circuit and check for a short to positive with the sensor disconnected as specified by the manufacturer.
- Check connector contact and circuit continuity for high resistance using the manufacturer’s diagnostic procedure.
- If the harness is sound, test Bank 1 Sensor 1 and the module’s sensor-amplifier circuit according to the manufacturer’s procedure.
Common fixes
- Clean and secure corroded Bank 1 Sensor 1 connector terminals.
- Repair a Vs− wire shorted to positive or replace the damaged section of harness.
- Replace Bank 1 Sensor 1 if testing confirms an internal short.
- Repair the module sensor-amplifier circuit only if the wiring and sensor test correctly.
Can I keep driving?
You can usually drive cautiously if the engine runs normally, but the faulty upstream reading can lead to excess fuel use and emissions. Stop driving if it runs severely rough or loses power.
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.