P0138Severity: Low
P0138 – Oxygen Sensor High Voltage (Bank 1 Sensor 2)
The downstream (post-catalyst) O2 sensor shows high voltage.
What it means
The post-catalyst oxygen sensor reports persistently high voltage (rich). A sensor fault, wiring short or a genuinely rich mixture can be the cause.
Symptoms
- Check-engine light
- Higher emissions
- Occasional fuel smell
Common causes
- Faulty downstream O2 sensor
- Wiring short
- Rich mixture
- Sensor contamination
With AutoMulti
AutoMulti reads this trouble code from your car in seconds, explains it in plain language with AI, lists the likely causes and helps you clear it when appropriate.
on theApp StoreSoonGet it onGoogle PlaySoon
Frequently asked questions
What does trouble code P0138 mean?
P0138 – Oxygen Sensor High Voltage (Bank 1 Sensor 2). The post-catalyst oxygen sensor reports persistently high voltage (rich). A sensor fault, wiring short or a genuinely rich mixture can be the cause.
Can I drive with a P0138 code?
It's usually not urgent, but finding and fixing the cause matters for emissions and fuel economy.