Just stopped at O'Reilly and scanned my 2003 Honda Accord 2.4 Vtec. came back with the problem codes listed in the title.

P0171 - System too lean bank 1
p2a00 - oxygen sensor 1 bank 1

I would like to do the easy one first. Is the problem code 0171 trigerred by a bad 02 sensor. Would it make more sense to change the o2 sensor first , and if issue still around to go for the fuel pressure regulator which most of the issues point to when it comes to 0171 code.

Please help.... I love my accord but poor gas mileage and bad performance caused by these two codes are pissing me off.

 

PO171 code is more than likely caused by #1 A defective oxygen sensor
#2 an ignition misfire or vacume leak-repair, # 3 Fuel injector problem.

With 2 codes like you have , I would expect fuel pressure and the MAF sensor also.
Take off the MAF and have O'reilys or an Auto Zone check it for you.

WheelBrokerAng

 

would you happen to know the exact location of the bank 1 sensor 1 on 2003 honda accord 4 cylinder engine.

 

Change the front O2 sensor first, there's a good chance that's the reason for P0171.

Down low, between the engine & firewall. Look where the exhaust system comes down from the engine. It's #16 in this picture.


And... unless it's a California car, it probably doesn't have an MAF sensor.

 

I'm having the same issue. Well, actually replaced the upstream o2 sensor, then got a code for the downstream one. Replaced that, erased codes, then 24 hours later got the codes above.
P0171 - System too lean bank 1
p2a00 - oxygen sensor 1 bank 1
Advance told me that perhaps I hadn't driven it enough after the codes were reset, so I erased them again and took to the road. Everything's running fine. 24 hours later P2A00 again. What next? I saw above that the MAF Sensor came up, but it's likely only on California cars. I have a Canadian 04 Civic EX.
Thoughts?

 

Look on your air filter housing. The MAF sensor is #15 in this picture. Your car either has one or it doesn't...