My heating system blowss cold air, even after driving for several miles. The check engine light comes on and my handheld computer indicates a thermostat sensor is reading lower than the regulator (?) will allow. I can, sometimes squeeze the top radiator hose and get hot air for a short period of time. When it is 7 degrees outside this is unacceptable. What else should I investigate?

AS FAR AS THE OVERHEAT ISSUE BLEED THE AIR OUT OF THE COOLING SYSTEM. FOR THE NO HEAT CHECK OPERATION OF TEMP BLEND DOOR AND FOR CLOGGED HEATER CORE

If that bottom hose is cold, it sounds like the radiator itself is not circulating.

Not a problem. I'm glad to help. As far as the vents, yes they run by vacuum. If the blend door or other door isn't opening or closing, you could draw cold air from one vent and warm in another.

Give it a try and let me know if you find anything. If you can't, I'll see if I can dig a vacuum diagram for the system ,may be you can find your problem
www.xcardiag.com

read the owner manual to see how the auto works. try the defrost mode whcih is a fail safe mode and should always come on unless a major system issue.

most likely a air bubble in your system. get it up to temp open up your reservoir use something that will fit in the opening and put coolant into it rev engine up a bit until you see bubbles coming up. when you did the engine did you replace cooling system parts like t-stat or water pump? purging the system of air will take a little while good luck hope that helps

the infomation u were given is 100% wrong! if the light is coming on then a problem exists in the OBD 2 engine control system, there will be a fault code stored for the check engine light, who told u this the dealer??

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.

My 05 sentra with 79k miles heat will warm up and then get cold after a mile of driving, we have tried to get the air pocket out, the mechanic stated he thought it could be a blown head gasket, another mechanic said it was a bad heater core. Any advice would be appreciated.

HI....
You don't have to worry about P0411. But you need to fix.
because the vehicle will burn more gas...
Let me Explain a little bit. of the SECONDARY AIR INJECTION SYSTEM.
Your vehicle use a Vaccum Electric pump. to reduce the HYDROCARBOM EMISSION , During a Cold start the System forces filtered fresh air into the exhaust stream in order to accelerate the catalystic operation.
The IAr is send to the exhaust passing from a check valve.
The code P 0411 , Can be a restriction on the hose coming from the Air pump to a Exhaust. or The hose damaged or pinched.
But the first step is check the operarion of the pump.
Check the Air pump relay. and fuse.

The pump Is located on Left Front Frame Rail, Forward of Fenderwell.

P1660. This code refer to a : Excessive Current or Voltage ON the system.
Check The ALTERNATOR for proper Voltage charging.
If the Alternator is charged more than 16v. replace the alternator.
Remember if you gave a Jump Cables of any time or day.

Any of this will the code P1660 come..
The ECM can BURN. For HIGH VOLTAGE, BE CAREFUL
After you check the Charging system. And detect that everything is in order, Clear the light.

PRINT THIS COMMENT and give to your mechanic....

I hope this will help on your problem.

THANK YOU FOR USE FIXYA>>

it may be your thermostat, the gauge on the dash is a dummy gauge, there is only three positions that it sees, dead cold, operating temp, and hot, so even though the needle looks fine it just means it s closer to operating temp then it is to cold,