Pre heater light not comeing on (c5 1.6hdi 2006)and i,am not sure that the fuel is being per heated ?how can i check

Make sure your fuse to the Fuel Pre Heat isn't blown. If it is you will need to replace the pre heater inside of the fuel filter housing.

check for air in the system . Bleed out at all bleed screws . crack the injector lines at the injectors and continue cranking until diesel drips from the nut. tighten and continue cranking. Check for fast crank speed and glo-plug operation

Do you have any white smoke coming from the exhaust when you turn it over , I assume it turns over. If not you our not getting fuel to your cylinders. The other thing is that they install a pre heater on a timer so it will pre-heat the cylinders before it will start. check those areas first

Check fuses end relays. Fuse could be blowin. If the lights don,t come on on the heater control panel for the different funtions, Mostly the fuse has (Blowin)

have your thermostate checked.

This sounds like your automatic climate control is starting to malfunction. Check to make sure your coolant is full, and temp is not fluctuating, and when your vehicle is warmed up, try using the low setting and feel for air temp. Is it warmer than if you turn it up? When at idle the vehicle is not producing heat the same as if you are driving, putting load on your engine and more air/fuel combustion means more heat, which is why you can feel heat while driving. Ideally you should feel heat as soon as the engine is warming up, getting hotter as it reaches peak temp of 190-210 degrees. You can try to make sure your water control valve is not blocked, and all electrical connections are secure. This will be located close to your firewall and connected to the coolant tubes that run into your firewall to your heater-core. Also use recirc (setting)to try to summon as much heat as possible, however ultimately, you may need to take you vehicle in for service. If it only warms when driving defrost will be an issue. Good luck.

Check the hoses going into the heater core.They should be hot to the touch.If they are then you could have a temperature door not working.If only one is hot and the other is just warm then the heater core is the problem.Also check the cooling system level.Make sure it is to the full hot in the over flow bottle.

What sensors did you replace? It sounds like a problem that could be caused by something in the evaporative emission system, like a faulty purge solenoid or evap cannister problem. Does the tank take fuel slowly when filling up? You could also have a faulty gas cap. That is the first thing I would look at. It is an integral part of the evap system. Hope this helps and best wishes.

P0016 - Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
P0030 - Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 1
P0031 - Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1
P0032 - Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 1
P0036 - Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 2
P0037 - Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 2
P0038 - Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 1 Sensor 2
P0050 - Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 1
P0051 - Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 1
P0052 - Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 1
P0053 - HO2S Heater Resistance Bank 1 Sensor 1 (PCM)
P0054 - HO2S Heater Resistance Bank 1 Sensor 2 (PCM)
P0056 - Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 2
P0057 - Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 2 Sensor 2
P0058 - Heated Oxygen Sensor (HO2S) Heater Circuit High Voltage Bank 2 Sensor 2
P0068 - Throttle Body Airflow Performance (PCM)
P0100 - MAF Sensor Circuit Insufficient Activity

You might wanna check and make sure the heater switch didn't go bad. It could even be the blower motor itself.