(MAP) Controlled Thermostats – Provide Several Engine Benefits

(MAP) Controlled Thermostats - Provide Several Benefits
(MAP) Controlled Thermostats - Provide Several Benefits

How Do (MAP) Controlled Thermostats Actually Work.

(MAP) Controlled Thermostats, are controlled by the engine’s electronic control unit (ECU).

This provides precise regulation of temperature, based on the engine’s loads.

(MAP) Controlled Thermostats, provide broader and faster operation than the traditional engine thermostat.

Consequently, conventional thermostats can only respond to changes in temperature caused by:

  • Heat From the Engine
  • And Cooling From the Radiator

So, why The Change After All These Years

As we push the engine closer to the desired 230-degree range; we needed a more advanced thermostat technology. (MAP) Controlled Thermostats, still use expanding wax. But, now they can control the temperature of the wax. To do this, they use a heating coil, surrounding the wax. Consequently, (MAP) Controlled Thermostats, can influence the temperature much faster. As a result, allowing the engine to operate; in various load and operating conditions.

This level of temperature control provides:

  • Optimum combustion; due to increased cylinder wall temperatures.
  • Reduced fuel consumption; due to reduced viscosity of the engine oil and consequently reduced frictional loss.
  • Lower pollution emissions; due to improved combustion.
  • Improved power output at full load; due to reduced coolant temperature.
  • Increased comfort; due to higher coolant temperatures. As a result, improved interior heating.

Under normal load conditions this will; stabilise the engine at a higher temperature. This causes the thermostat to stay closed longer. As a result, obtaining benefits such as good power response; lower emissions and reduced friction. There is also a heating coil. This additional heat source allows the wax to expand quicker. Consequently, opening the thermostat fully; regardless of actual coolant temperature.

(MAP) Controlled Thermostats - Provide Several Benefits
(MAP) Controlled Thermostats – Provide Several Benefits

This temperature control allows for:

  • Good fuel economy
  • Better emissions
  • Faster warm up
  • And, better comfort for the driver inside the vehicle

Sometimes the (ECU) may decide that a cooler engine temperature; is required for higher speed or high-load operations. Consequently, the heating coil is activated and the thermostat will; open at a lower coolant temperature giving better performance. Once the (ECU) sees that those conditions have been met, the heating coil is deactivated. As a result, the thermostat returns to normal wax operation.

This, in effect, gives the (ECU) a number of new operating modes; unavailable with a standard wax thermostat. The beauty of this concept and design is that; it operates completely unnoticed by the driver. And, continues over the life of the thermostat with no required service.

(MAP) Controlled Thermostats are maintenance-free. And, are designed to last for the life of the engine. However, external factors such as low-grade coolant along with; failure to regularly service the coolant can lead to material failure. Other possible causes of failure include; previous damage caused by thermal overloading or contamination.

Engine Codes For (MAP) Controlled Thermostats

Being able to see engine codes when there is a fault is an added feature. On these systems, there are two ways the engine (ECU) knows there is a problem. The (ECU) is able to determine if there is a short or open circuit. It does this through measuring voltage drops to determine; if the circuit and components are functioning normally. When the (ECU) detects a problem, it will set a code.

The most common codes P0597, P0598 and P0599 all refer to, an electronically controlled engine thermostat.

Possible Repair Procedures Include:

  • Remove and inspect the electrical connector. Remove any corrosion using baking soda or by scraping. Apply electro grease and confirm a tight connection.
  • Inspect the coolant level in the radiator. Low levels of coolant will set a code by; causing the electronic thermostat to overheat.
  • Remove the electrical connector and check the resistance values on the thermostat. For this procedure you will need a service manual; or the necessary information found online.
(MAP) Controlled Thermostats
(MAP) Controlled Thermostats

Thermostat Testing For (MAP) Controlled Thermostats

So, the first component to check is the circuit. It is possible you may have a code for an open or short in the circuit. The first thing to do is clear the code. If the code comes back immediately, you have confirmed the problem. If not, the problem is in the heater coil or the circuit. You can determine if the coil is bad by measuring its resistance. Measure the resistance and compare the specification in the service information. If you have no resistance the heating coil is damaged. You can also use a multimeter to determine if the (ECU) is sending voltage to the coil.


Finally, vehicle manufacturers are under intense pressure; to produce cars and trucks that produce fewer emissions. So, closely regulating the cooling system is one way to do that. Also, by achieving finer control of existing systems and using; different techniques to regulate temperatures.

Please Share Danny’s Engineportal.com News