When you disconnect the battery, all of the codes get erased. The 1-1-3 will eventually come back after so many drive cycles. While it could be the O2 sensor, I would first look for any potential air leaks that would allow non-metered air into the intake - cracked vacuum lines or elbows. Loose connections from the air filter box to the throttle body. An exhaust leak before the cat.

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Keeping it running is better than buying new