I have two issues on my 1998 Buick LeSabre Limited.
Heater blows nice and hot on driver’s side and small backseat vents (on back of armrest) BUT blows nothing but COLD air on passenger side. This is true upper, middle, lower vents.
The check engine light just recently popped a p0171 code, bank 1.
Is there any chance these are related (vacuum leak)? If anyone has any ideas for fixing either/or, I would appreciate any guidance.