I’m a US citizen and a Canadian Permanent Resident. During my visit to my terminally ill mother in the US last year my passport expired. I just noticed it and am returning to my home in Canada at the end of February. With the Covid epidemic going on it will take too long to renew my passport. I do have my valid Canadian permanent resident card and since my passport is expired and can’t fly I’m planning on crossing by Land. Will I have any problems entering Canada with my Canadian permanent resident card and expired US passport. I do have my birth certificate and my valid US drivers license to show that I am who I say am.
A late answer, but anyway, a permanent resident has a statutory, absolute right to enter Canada, once their status is established by a valid permanent resident card.
From recent experiences, you might still be reminded of the "need" of a passport; but it is not a big deal unless your identity is questioned. It might be that in the past passport stamps are often used as evidence when the officer examines the compliance with residency obligations, but nowadays (almost) everything is electronically recorded.
In fact I could not find any legal requirement for a permanent resident to have a passport when physically entering Canada, despite certain IRCC/CBSA websites implying or having implied so. Although for international flights, the Secure Air Travel Regulations does obligate the airlines to check a passport or NEXUS card before boarding a passenger. A PR card alone will not accepted by the airlines as a travel document.
However, at airports, a permanent resident card alone is accepted by the automatic kiosks. But a non-US/Canadian-citizen NEXUS members without a passport may not be able to use the NEXUS lane or kiosks.