OBD2 Error Code P0138: How to Fix It

Q: What causes OBD2 code P0138?

P0138 is typically caused by a faulty downstream oxygen sensor, damaged wiring or connectors, exhaust leaks near the sensor, or less commonly, a malfunctioning PCM. The sensor may be reading constant high voltage due to age, contamination, or electrical issues.

Q: Can I drive with error code P0138?

You can drive short distances with P0138, but it should be fixed promptly. This code can cause reduced fuel economy, increased emissions, and potential damage to the catalytic converter if left unaddressed for extended periods.

Q: How much does it cost to fix P0138?

Fixing P0138 typically costs $150-$400 if you need to replace the oxygen sensor. DIY replacement costs $50-$150 for the sensor itself, while professional repair adds labor costs of $100-$250 depending on vehicle accessibility and local shop rates.

Q: How long do oxygen sensors last?

Oxygen sensors typically last 60,000-100,000 miles, but can fail earlier due to contamination from oil leaks, coolant leaks, or poor fuel quality. Downstream sensors (like the one in P0138) often last longer than upstream sensors due to less exposure to exhaust heat.

Q: Will P0138 cause my car to fail emissions testing?

Yes, P0138 will likely cause your vehicle to fail emissions testing. This code indicates the emissions monitoring system isn't working properly, which is required for passing emissions tests in most areas. The code must be resolved and the system must complete its readiness monitors.

Abstract

OBD2 error code P0138 indicates that your vehicle's oxygen sensor 2 in Bank 1 is reading higher voltage than normal. This downstream oxygen sensor monitors the catalytic converter's efficiency, and when it malfunctions, it can affect fuel economy and emissions.