I recently discovered that it is not required to have a valid Permanent Resident Card when returning to Canada by car.
As the application process for renewal of these cards is rather long (currently more than 3 months), it may be useful to know that we can still travel to the US and return as long as we travel over land in a private vehicle. This is described on the web site of Immigration Canada.
Note that you will need your original IMM-1000 form instead.
While I returned from the US earlier this week, I confirmed with the immigration officer that this was correct. The only drawback from this procedure is that you will need to enter the immigration office at the border so they can fully validate your status since the computer at the booth doesn’t have enough information.
You cannot enter by plane using the IMM-1000, only by private car.
Keep this as a plan B in case you need to travel, and your PRC is lost or expired. Check with immigration Canada before leaving as these procedures may change over time.