Walker, 18, initially joined the Cumbrians on loan at the start of the season but dislocated his right shoulder a month into his stay.
He had an operation on his shoulder and did his rehab with the PNE medical staff at Euxton.
Earlier in January, North End officially recalled him from the loan to allow him to be in the squad for the FA Cup tie at Wycombe Wanderers.
Walker was on the bench that day but didn't come on.
With North End having bolstered their squad with new signings during the transfer window and having got players back available after injury, it was decided to allow Walker to resume his loan at Carlisle and get a run of first-team games under his belt.
The loan was agreed earlier in the week, there being a slight delay to it resuming as Carlisle waited for their squad to come out of isolation after Cvoid-19 issues.
Walker made his PNE debut in December 2018 against Aston Villa, becoming North End's youngest player to appear in a league game at the age of 16.
He is the third player to depart Deepdale on loan this week, following on from Josh Harrop (Ipswich) and Jayden Stockley (Charlton).
Stockley made his debut for Charlton as a substitute in their 2-2 draw with Swindon on Saturday but Harrop missed Ipswich's defeat to Peterborough after returning a positive Covid-19 test.
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