The come-from-behind win, the third for PNB, also ensured that they finish at the top of Pool B with nine points.
They were joined in the last four by local outfit Western Railway, who lost 5-6 to Hockey Bhopal, and yet managed to make it to the last four as the second-best in Pool B behind the Punjab bankmen.
However, after switching ends, CAG adopted a defensive approach and went into a shell to yield the advantage to PNB.
PNB's hardwork was rewarded as an unchallenged Naveen Antil fired past the pads of CAG goalkeeper Harjeet Singh to equalise in the 51st minute.
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Four minutes later, PNB doubled the lead when Gagandeep Singh slammed home from the top of 'D' after receiving Hardeep Singh's cross from the right.
(Reopens SPB2)
Later in the concluding Pool A league match played under lights, RCF (Rail Coach Factory), Kapurthala scored a stunning 6-4 win against defending champions Air India.
However, both team advanced to the semi-final from this pool.
RCF finished in pole position with 10 points and Air India were placed second with 9 points.
Semi-final line-up: Punjab National Bank vs Air India RCF vs Western Railway.