I think you transposed a number, not aware of a 1071 code..
Should be a P0171 which is Bank1 Lean code.
Not fatal by any means, just means that the system has reached the max fuel trim on that bank based off of the O2 sensor data, in this case best to clear the code ONCE then see if it comes back after MANY complete drive cycles (drive cycles a from cold start to fully warmed and driven for a short period then shut off and allowed to fully cool off).
If it comes back THEN start searching for the reason.
Continued operation with Lean condition code will eventually poisoning and damaging the cats, O2 sensors.
Dump the Scan gauge for real diagnostics, they often cannot go deep enough for good diagnosis. Get a real standalone scanner, they are dirt cheap now days and they can give you much more data access than a scan gauge can ever do and not to mention no need to search the Internet for what the code means most standalone readers have that info built in (I have a $70 one from HF which tells me what the code means and what the most possible items may cause that code).
In this case, upstream O2 sensor is detecting a lean condition on bank 1, IF it was really from High altitude, I suspect you would have also had code for Bank 2 lean condition at the same time.
Now, you could simply have a lazy Bank 1 O2 sensor (they do go bad) OR you may have a vacuum leak near bank 2 intake manifold.. Or you could have a CRACKED OR LEAKING Bank 1 exhaust manifold or manifold gasket(extremely common on all of the "Modular" blocks) which believe it or not can leak enough to affect the Oxy level detected by the O2 sensor.. IF you have a exhaust manifold leak, this one can cause serious over fueling and running extremely Rich on that bank (computer turns up the fuel trim to compensate for the lean condition), this one you will smell excessively rich fuel smell on the exhaust and also will quickly poison your cats..
Or it could have been nothing more than a glitch.. Only time will tell.
