Hi there I have volvo s40 2.0 t4 1998, automatic, full option... digital temperature display... I had problems 2 years ago with my engine, than I have changed the engine, and took the newer one, its model is 2003.. but same. have no problems with the temperature, it comes to 102 degrees and the cooling fan turns on, than it goes down... I live in Saudi Arabia, so the weather is very hot... but I think there is no problem with my temperature... no water leaking, no oil leaking, it takes around 8-11 liters per 100 kilometers, depends on the way I drive... so everything feels normal... before the summer, I felt that my volvo has become weaker and slower... when it is on idle no smoke of any kind, when I press the gas and hold it, every thing is normal, no smoke, but when i release it and the RPM returns to normal (900) there is white smoke coming out of the exhaust... so the smoke comes only after the acceleration, even when I drive... between the traffic lights, when accelerate no smoke, when I release the gas pedal the smoke starts to come out... my mechanic told me that my turbo is broken... I don't want to change anything before I ask someone... so please tel me what do you think.. thanks a lot

Hey Brian ,
ICP - Integrated control panel
RCC - Remote Climate Control Module
Integrated Control Panel-Electronic Automatic Temperature Control
Control Assembly The Taurus, Sable vehicles group together the following systems into a single integrated control panel:

• AM/FM stereo radio
• clock
• rear window defroster switch
• electronic automatic temperature control (EATC)
• full-logic cassette tape player
• compact disc player control (optional)

The remote climate control module is mounted to the A/C evaporator housing behind the integrated control panel. The integrated control panel is connected to the remote climate control module with a dedicated two-wire communication link. The integrated control panel EATC features:

• a vacuum fluorescent display (VFD) for displaying set temperature, ambient temperature, function and diagnostic trouble codes (DTCs).
• electro-luminescent backlighting for all buttons and graphics.
• function override buttons.
• temperature control and blower speed rocker switches.

Thermostat again? Tempeture sensor maybe bad....

That's not a problem as far as its not overheating. and if the radiator is bad or there was a leak then the car will be high not low. and i think your your Thermostat is open all the time that's maybe why the car is always Low on Temperature.

Sounds like a faulty injector, had the same problem about 2 years ago cost over £1500 to have new injectors fitted.

It might be worth trying some redex or similar cleaning product incase its just blocked.

Oil filter is provided by year,make, model of your vehicle at the parts store. ---
Oil and fluids Oil quality
Engine oil must meet the minimum ILSAC specification GF-2, including ACEA A1, API SJ, SJ/CF and SJ/Energy Conserving.
Your Volvo has been certified to standards using ILSAC oil specification GF-2 5W-30. Volvo recommends use of oil with a quality rating equal to or higher than ILSAC GF-2. Equivalent and better oils include ACEA A1, API SJ, SJ/CF, and SJ/Energy conserving. Lower quality oils may not offer the same fuel economy, engine performance, or engine protection.
Volvo Cars recommends Castrol. Depending on your driving habits, premium or synthetic oils may provide superior fuel economy and engine protection. Consult your Volvo retailer for recommendations on premium or synthetic oils. Oil additives must not be used. NOTE: Synthetic oil is not used when the oil is changed at the normal maintenance is carried out. This oil is only used at customer request, at additional charge. Please consult your Volvo retailer. Operation in hot climates.
When temperatures exceed 86° F (30° C) in your area, Volvo recommends, for the protection of your engine, that you use a heavier weight oil, such as SAE 10W-30. See the viscosity chart below. Oil viscosity (stable ambient temperatures)
Operation in temperate climates
Incorrect viscosity oil can shorten engine life. Under normal use when temperatures do not exceed 86° F (30° C), SAE 5W-30 will provide good fuel economy and engine protection. See the viscosity chart above. Extreme engine operation
Synthetic oils meeting SAE 10W-30 and complying with oil quality requirements are recommended for driving in areas of sustained temperature extremes (hot or cold), when towing a trailer over long distances, and for prolonged driving in mountainous areas. Changing oil and oil filter
Oil and oil filter changes should be made at 7,500 mile (12,000 km) intervals. Volvo does not recommend the use of oil additives.
Synthetic oil is not used when the oil is changed at the normal maintenance intervals except at ower request and at additional charge. Please consult your Volvo retailer.

undo the clip on the highest hot water hose to release any trapped air(engine hot)
when was the last time it was backflushed and antifreze replaced??

The lights indicate a problem with the transmission. The fact that the engine wont start, leads me to believe that the PNP (neutral safety switch) is the problem. You will have to have the vehicle scanned to make sure.

Volvo Radiator, Thermostat and Sensors Your cooling system's temperature controls include all coolant temperature sensors, Volvo thermostat, Volvo radiator or expansion tank cap, cooling fan(s) and fan clutch (if equipped). These cooling system parts function primarily independent of the engine but control the engine either through cooling or by sending control signals to your Volvo's electronic systems.
The Volvo thermostat is a spring-loaded valve that opens and closes based on the temperature of the coolant flowing through it. A high temperature reading followed by a drop to normal temperature (or a continuously low temperature) is a common first sign of a sticking Volvo thermostat. However, many other conditions may cause these symptoms, so you need to know how to eliminate each possibility.
The Volvo radiator or expansion tank cap is also a spring-loaded valve reacting to system pressure. It serves to maintain proper system coolant level at predetermined pressures. It must always be replaced with an exact replacement cap with the same pressure setting. Never use other caps except for short-term emergencies!
A belt-driven fan blade for pulling air through the Volvo radiator is usually on the Volvo water pump pulley and should have a fan clutch to control it. The fan clutch allows the fan to turn with the belt at low engine speed and "free-wheel" at higher speeds. A bad fan clutch either doesn't allow the fan to spin at low speed (overheating in traffic) or doesn't allow it to free-wheel at high speed (potential overheating on highway or reduced gas mileage).
An electric fan can be either by itself (usually front-wheel drive) or auxiliary (used with a mechanical fan). Both types are controlled via a temperature sensor - in the Volvo radiator or upper Volvo radiator hose or on the Volvo thermostat or Volvo water pump housing. This sensor is usually an on/off type switch with a fixed temperature setting. (Some vehicles may have 2-3 settings for multi-speed fans.) This sensor is commonly called an "auxilliary fan switch".
Other common temperature sensors are: 1) gauge sender (variable output); 2) warning light sender (on/off type); 3) lambda and/or fuel injection sensor(s) (variable to control fuel injection settings); 4) thermo-time switch (cold start valve control). Your Volvo may have other sensors as well.
Temperature control is critical to both performance and emission control. Unfortunately, this system is the most difficult to troubleshoot without proper equipment and diagrams. It's even more difficult with computers that adjust timing, idle speed, vacuum and fuel delivery automatically to make up for potentially faulty temperature sensor signals.
Maintenance of your cooling system sensors is virtually impossible since there's nothing really to "maintain". Keeping them clean both internally (coolant replacement) and externally (engine cleaning) is the best way to ensure trouble-free driving. Checking and replacing all parts at the factory-recommended time or mileage limits helps as well

Buy a scanner or go to Autozone and have them pull the codes out. get back to me with the codes and I'll figure it out for you.
But the fan could be the relay or the coolant temperature sensor and ECU that controls the circuit. Have the coolant , hoses and thermostat been changed lately. Start with those things.
Get the shop manual and test the coolant temperature sensor,relay and ECU. These are simple checks usually a visual inspectionor a little probing with a Digital Voltmeter will solve the problem.

How long since the fluid was replaced?