I have a 000 Nissan Sentra that has 3 codes.. 134, 403 and 1126.. Please tell me what they mean and how to fix them

A stoat is a small weasel. Do they have signal lights for them where you live?
Do you have a check engine light? Or any kind of advisory light (check gauges, etc)? If so, this information should be included with your question. Recommend you bring your Nissan to a qualified mechanic and explain what's happening and have them troubleshoot and correct your issue.
If you think you want to correct it yourself, please resubmit your question and provide details. Check engine light on/off, any codes. When it quits, can you restart it right away. If not, are you getting spark and fuel. Without information like this, no one can tell you what's wrong and what to do to fix it.

check charging fuse then check battery voltage engine running 13.5 plus volts and with acc. on same voltage .

Crank shaft sensors often fail without triggering a code. But in its early stages, a check engine light may be on. Symtoms of a bad crank sensor are: poor acceleration ( lack of power ) rough idle, ETC. sometimes you may be able to start it normally, and other times it takes 3 or more times. If the check engine light is on take it to a auto parts store and thy can read the code for free. To tell if that's the problem. God-Bless!

check engine light on means some fault codes stored in your engine control module.
use this tool clear the fault code p1320.

Go to AutoZone. They will hook up their computer tester, and tell you what the code means.

Some ECUs require a reset and this is often done via the diagnostic code scanner itself. Auto parts stores will scan free, but I don't know if they would charge to reset the error register. You would have to call them and ask.

Its telling you that you have a recommended service coming up at 30K miles. The dealer will reset the light when you bring the car in. Nissan recommends you to do your maintence's every 7500 miles. A 30K service will consist of an oil change, change air filter, coolant flush, replace PCV valve, in cabin air filter, along with checking many other systems in your vehicle. Hope this helps.

How To How to Reset the Computer on a Nissan Sentra When the check engine light illuminates on the dash in a Nissan
Sentra, it is an indication that the computer has recognized a problem within its sphere of influence. Once the problem has been addressed and corrective action completed, the computer can be reset by erasing the existing codes.
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Instructions Things You'll Need:

• Code scanner

1. Step 1 Insert the code scanner's connector into the OBD port located under the dash to the right of the steering column.
   
2. Step 2 Turn the ignition key to the run position. Make sure the engine is off.
   
3. Step 3 Press the button for "Read" on the code scanner. Within less than 1 minute, the scanner will display all failure codes that are stored in its memory.
   
4. Step 4 Write down the failure codes displayed by the scanner. Cross-reference the codes with the code sheet that comes with the scanner. The codes are displayed with a letter followed by a four-digit number code. Deciphering these codes by cross-referencing them with the code sheet offers an explanation of the failure.
   
5. Step 5 Turn the key off. Correct the failure so that the computer can be reset.
   
6. Step 6 Turn the ignition key on, keeping the engine off. Press the "Erase" button on the scanner. Start the vehicle and allow it to run for 5 minutes. Watch for the check engine light to come back on. If it does, the problem has not been corrected. If it stays off, the problem has been successfully resolved.
   

you may havta replace the air flow meter module.

The check engine light could be on for any number of reasons, particularly in the light that the car was flooded. If it is drivable, take the car to an auto parts store like Autozone and ask them to hook up their scan tool to your cars computer and they can read the codes that are causing the light to come on. They can also tell you what the codes mean and give you a print out.

If the codes and information is not helpful, post up the codes here and I will see if I can be of further assistance.