Tip & How-To about Mercedes-Benz E-Class

ECT - Engine Coolant Temperature sensor

2.2) ECT - Engine Coolant Temperature (sensor)


What is it? This is small electrical device for measuring the coolant temperature in the engine


Where is it located? It is usually located on the engine near to the thermostat housing. The ECT is sited on the 'hot' side of the thermostat so that it senses the coolant/engine temperature before the thermostat opens and allows coolant to flow through the radiator.


How does it work? Modern temperature sensors consist of a thermistor in a sealed unit. As the temperature rises the electrical resistance varies proportionately; some thermistors increase their resistance with temperature (PTC - positive temperature correlation) whilst others decrease their resistance (NTC - negative temperature correlation). When the engine is cold at start up the coolant sensor sends an appropriate signal to the ECU. The ECU responds by increasing the length of the injection cycles to enrich the combustion mix. This is an electronic equivalent of pulling the 'choke' out on a carburetor. As the engine warms up the signals from the coolant sensor cause the ECU to shorten the injection cycles making the fuel mix progressively leaner. The process of coolant sensor and ECU interaction explains why engines have a slightly faster idle when starting cold than when running hot.


Symptoms of faulty coolant sensor

Associated OBD2 error codes DTCs: P0115 - P119; P0125, P0126, P0128


  • Poor starting - If the coolant sensor reports in error that the engine is warm the ECU will not enrich the fuel mix at ignition. The engine will falter at idle if it is not given additional help by the driver by pressing on the accelerator pedal to maintain speed. Once the engine has warmed up the engine will behave correctly.
  • Fast/erratic idle, Poor fuel economy - conversely if the coolant sensor reports in error that the engine is permanently 'cold' the ECU will keep the fuel mix rich. This is OK at start up but will become more noticeable when the engine is hot; idle will be fast and lumpy. Fuel consumption will be high due the permanently rich fuel mix set by the ECU.
  • Excessive emissions - the enriched fuel mix delivered in response to ECT signal error causes the exhaust to be heavy in un-burnt hydrocarbons. This often results in 'emission test' failure.


How to check? Most often the coolant sensor is quite separate to the temperature sender, so a correct read-out on the dash board does not necessarily indicate correct sensor function. Using a voltmeter the resistance across the electrical terminals on the sensor can be measured. By removing the device from the car and putting the end of the sensor in a pan of hot water it should be possible to see an immediate change in resistance, it does not matter so much that the resistance goes up or down but that there is a discernable change with change in temperature. Generally high resistance equates to cold temperatures and vice versa. If there is no resistance change commensurate with temperature change then the sensor is at fault. If there is simply no resistance measurable (open circuit) then the sensor is at fault. If the sensor is working correctly check the connector, the wiring and the wiring insulation for faults and possible shorting.


How to fix? Replace if found faulty



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2 Answers

where is the engine coolant temperature sensor low input located on a kia 2007 spectra


Not low input sensor...P0117 KIA - Engine Coolant Temperature Sensor 1 Circuit Low Input

Possible causes
Low engine coolant level
Faulty Engine Coolant Temperature (ECT) sensor
Faulty engine coolant thermostat
Engine Coolant Temperature (ECT) sensor harness is open or shorted
Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Just replace coolant temperature sending unit....
11_14_2017_9_19_36_pm.jpeg

Nov 14, 2017 | Kia Cars & Trucks

1 Answer

What does code P 119 mean on my Cadillac 1994 Seville STS


P0119 Cadillac Engine Coolant Temperature Circuit Intermittent
Possible causes - Low engine coolant level
- Faulty Engine Coolant Temperature (ECT) sensor
- Faulty engine coolant thermostat
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Engine Coolant Temperature (ECT) sensor electrical circuit poor connection What about the obd code? The Engine Control Module (ECM) detected an erratic signal from the engine Coolant Temperature (ECT) sensor during the system monitor test Symptoms - Engine Light ON (or Service Engine Soon Warning Light) P0119 Cadillac Description The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
P119 or P0119 ?

P119 - Shorted Fuel Injector Problem
or

Feb 18, 2016 | Cadillac Cars & Trucks

1 Answer

po115


The Code P0115 is a coolant sensor error (measures temperature of engine coolant). First make sure that you have enough coolant in the engine. If there is enough coolant and you still get the error then the following explanation should help:-

What is it?
This is small electrical device for measuring the coolant temperature in the engine

Where is it located? It is usually located on the engine near to the thermostat housing. The ECT is sited on the 'hot' side of the thermostat so that it senses the coolant/engine temperature before the thermostat opens and allows coolant to flow through the radiator.

How does it work? Modern temperature sensors consist of a thermistor in a sealed unit. As the temperature rises the electrical resistance varies proportionately; some thermistors increase their resistance with temperature (PTC - positive temperature correlation) whilst others decrease their resistance (NTC - negative temperature correlation). When the engine is cold at start up the coolant sensor sends an appropriate signal to the ECU. The ECU responds by increasing the length of the injection cycles to enrich the combustion mix. This is an electronic equivalent of pulling the 'choke' out on a carburetor. As the engine warms up the signals from the coolant sensor cause the ECU to shorten the injection cycles making the fuel mix progressively leaner. The process of coolant sensor and ECU interaction explains why engines have a slightly faster idle when starting cold than when running hot.

Symptoms of faulty coolant sensor
Associated OBD2 error codes DTCs: P0115 - P119; P0125, P0126, P0128

  • 2.2a Poor starting - If the coolant sensor reports in error that the engine is warm the ECU (electronic control unit) will not enrich the fuel mix at ignition. The engine will falter at idle if it is not given additional help by the driver by pressing on the accelerator pedal to maintain speed. Once the engine has warmed up the engine will behave correctly.
  • 2.2b Fast/erratic idle, Poor fuel economy - conversely ifthe coolant sensor reports in error that the engine is permanently 'cold' the ECU (electronic control unit) will keep the fuel mix rich. This is OK at start up but will become more noticeable when the engine is hot; idle will be fast and lumpy. Fuel consumption will be high due the permanently rich fuel mix set by the ECU.
  • 2.2c Excessive emissions - the enriched fuel mix delivered in response to ECT (engine coolant temperature) signal error causes the exhaust to be heavy in un-burnt hydrocarbons. This often results in 'emission test' failure.

How to check? Most often the coolant sensor is quite separate to the temperature sender, so a correct read-out on the dash board does not necessarily indicate correct sensor function. Usinga voltmeter the resistance across the electrical terminals on the sensor can be measured. By removing the device from the car and putting the end of the sensor in a pan of hot water it should be possible to see an immediate change in resistance, it does not matter so much that the resistance goes up or down but that there is a discernable change with change in temperature. Generally high resistance equates to cold temperatures and vice versa. If there is no resistance change commensurate with temperature change then the sensor is at fault. If there is simply no resistance measurable (open circuit) then the sensor is at fault. If the sensor is working correctly check the connector, the wiring and the wiring insulation for faults and possible shorting.

How to fix? Replace if found faulty

May 25, 2014 | 2001 Hyundai XG300

1 Answer

corolla, 1999, P0125


P0125 TOYOTA - Insufficient Coolant Temperature for Closed Loop Fuel Control

Possible causes- Low engine coolant level
- Leaking or stuck open thermostat
- Faulty Engine Coolant Temperature (ECT) sensor
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Oct 14, 2012 | 2001 Toyota Corolla

1 Answer

code 1 senser P0118 on a 2004 V.W beetle dicesel


P0118 for Volkswagen - (ECT) Engine Colant Temperature Circuit High

Symptoms:- Engine Light ON (or Service Engine Soon Warning Light)

Possible causes:
(Inspect the following... Repair/Replace if necessary)
- Low engine coolant level
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Engine Coolant Temperature (ECT) sensor electrical circuit poor connection
- Faulty Engine Coolant Temperature (ECT) sensor
- Faulty engine coolant thermostat

P0118 VOLKSWAGEN Description: The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the (ECM) as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
When is the code detected?:When an excessively high voltage from the sensor is sent to ECM.

I hope this helps! Let me know if you need further assistance.

Mar 08, 2012 | Mercedes-Benz C Cars & Trucks

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