Honda accord 2007 service code A23 what does this mean?

The oil service light must be reset, refer to the owners manual.

A13 is broken down to A, 1, and 3.

A means you have to change your oil.
1 means you need your tires rotated.
3 means you need to change your transmission fluid.

This is a service required warning light
B" indicates the following services are due:
- Change engine oil and filter, inspect brakes, check parking brake adjustment - Inspect : steering components, suspension components, rubber boots, brake lines, fuel lines, exhaust system, fluid levels and conditions "1" indicates: - Rotate tires

it means the car needs service. The error will be listed in the computer codes, pull those and proceed.

HONDA do not make radios .They only affix their badge onto
radios made by the large manufacturers (ALPINE , BLAUPUNKT etc).

First try https://radio-navicode.honda.com/
If so , then if the above suggestion is not successful ,then unfortunately the code will not be available for free (or cheap ) from anywhere on the Internet.

Main Dealer or a Decoding Service only

not sure if you are talkin about a ecu code but A 123 is a type of battery that may be used in the honda

How did you get the code? It doesn't show up on the check engine light list
http://www.engine-light-help.com/honda-check-engine-light.html

that light is a service light to remind u the car is due for a service

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Time for oil change