P2C65: O2 Sensor Out of Range During Deceleration Bank 1 Sensor 3

What it means

The Bank 1 Sensor 3 oxygen sensor signal is outside the expected range during deceleration.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Bank 1 Sensor 3 monitors oxygen in the exhaust downstream on bank 1, and the module checks whether its signal responds appropriately during deceleration. This code sets when that signal falls outside the expected range during deceleration, such as when the sensor cannot follow the oxygen change during fuel cut.

Common causes

Most likely first.

1. Sensor unable to follow oxygen spike during fuel cut
2. Sensor response time degraded with age

Symptoms

• Check engine light on
• Increased fuel consumption
• Possible rough idle or hesitation
• Failed emissions test

How to diagnose it

1. Save freeze-frame data and note engine speed, load, and deceleration conditions associated with the fault.
2. Use a scan tool to observe Bank 1 Sensor 3 response during a controlled deceleration and compare it with the expected behavior in the manufacturer's service information.
3. Inspect the sensor connector and harness for heat damage, chafing, loose pins, or poor connections.
4. Check for exhaust leaks near Bank 1 Sensor 3 that could alter the oxygen reaching the sensor during deceleration.
5. If the wiring and exhaust are sound, test sensor response and response time using the manufacturer's procedure.

Common fixes

• Repair damaged or loose Bank 1 Sensor 3 wiring or connector terminals.
• Repair an exhaust leak near the sensor if found.
• Replace Bank 1 Sensor 3 if testing confirms sluggish or out-of-range response.
• Clear the code and confirm sensor response during a suitable drive cycle.

Can I keep driving?

You can generally drive gently if the engine runs normally, but emissions performance and fuel economy may suffer. Avoid hard acceleration until the sensor response is checked, especially if hesitation develops.