P0140
O2 Sensor No Activity (Bank 1 Sensor 2)
low
i Description
The downstream O2 sensor on Bank 1 (after the catalytic converter) is showing no activity. This sensor should show a relatively steady voltage indicating the catalytic converter is working, but the ECU detects no voltage changes at all.
? Common Causes
- Failed downstream O2 sensor
- Wiring issue to sensor
- Blown heater fuse
- Exhaust leak near sensor
! Symptoms
- Check engine light
- No noticeable driveability symptoms
- Failed emissions test
# Diagnostic Steps
- Monitor downstream O2 sensor voltage (should show some activity)
- Check wiring and connector
- Test heater circuit
- Replace sensor if no signal
⚙ Typical Fix
Replace the downstream O2 sensor on Bank 1.
Parts Needed
O2 sensor (downstream, Bank 1)
Estimated Cost
$100-$300
↔ Related Codes
Q Frequently Asked Questions
Yes. The downstream sensor is primarily for catalyst monitoring. Driveability is not affected, but you will fail an emissions test.
☞ Learn More
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