Have you checked your suction lines.
Yes it could and so could a stuck open thermostat or a plugged heater core or a faulty temperature blend door actuator.
This code is for the exhaust cam actuator timing system. There are a few things that can cause this. Anything from the actuator solenoid, to the actuator, to an internal engine problem. - Tech JK ---------------------------
Could be, low on coolant, stuck open thermostat, plugged heater core, faulty temp blend door actuator,
Not a whole of symptoms to work with here...The most common cause of "... heater not working..." is a failed temperature blend door actuator motor.See "Related Questions" below for more
There are a couple of reasons why a 1999 Oldsmobile Alero ac heater to stop working. The heater coil may need to be replaced or the HVAC blower motor may need to be replaced.
Your heater relay switch may be bad
Check fuse if the blower is not working. If it is then replace your heater core. if its not then replace your fan switch.
Bad heater core.
Low on coolant, thermostat stuck open, blend door actuator broken or stuck, plugged heater core to name a few.
A squealing heater is more than likely a fan belt. It may be loose, or it may be worn and need replaced.
Your heater core behind the glove box has gone bad and needs to be replaced.
now when you say replaced heater fan multi speed are talking the fan or the switch because ther is a fan speed resitor that can go bad and fan only works on high speed which can cause conector to get very hot and cause insolation on the wires to melt and cause a short in the harness making fan run constantly.