  This article completes a former work where part of the O(p^6) low-energy
constants entering in the pi pi scattering were estimated. Some resonance
contributions were missed in former calculations and slight differences
appeared with respect to our outcome. Here, we provide the full results for all
the contributing O(p^6) couplings. We also perform a reanalysis of the hadronic
inputs used for the estimation (resonance masses, widths...). Their reliability
was checked together with the impact of the input uncertainties on the
determinations of the chiral couplings and the scattering lengths a^I_J. Our
outcome is found in agreement with former works though with slightly larger
errors. However, the effect in the final values of the a^I_J is negligible
after combining them with the other uncertainties. Based on this consistency,
we conclude that the previous scattering length determinations seem to be
rather solid and reliable, with the cO(p^6) low-energy constants quite under
control. Nevertheless, the uncertainties found in the present work point out
the limitation on further improvements unless the precision of the O(p^6)
couplings is properly increased.
