. . . does it make a different if the offence is indictable or summary ?
Yes. If the conviction is based on an indictable offence, there is a total prohibition for
FOUR years from the date of conviction.
For a summary offence, the impact depends on the sentence.
Anyone convicted in Canada of an offence for driving while impaired or driving with a BAC over 80 milligrams, is almost certainly subject to a term of probation.
For so long as the PR is on probation he or she is
NOT eligible for a grant of citizenship. In particular, he or she is
prohibited from obtaining citizenship.
Thus, a PR must wait until he or she has completed the probation and is in effect discharged before becoming eligible to apply.
Moreover, days on probation do not count toward meeting the PR presence requirement. Thus, from the date a PR was given probation until the date the PR has completed probation, those days will
NOT count toward presence in Canada. This can have a big impact on the PR's future eligibility since all days which do count must be within the previous six years (current requirement) or within the preceding five years (when C-6 change to 3/5 rule takes effect). Thus, for example, if the PR is on probation for two full years or more, that could mean having to start over in terms of counting days.
I am not familiar with the typical length of probation in these sorts of cases. Anyone in this situation should be aware how long he or she is on probation.
Minor criminality is one of the more common reasons why long-term PRs well settled in Canada have difficulty becoming a citizen.