I have Audi A6 2,4, 1998. A month ago I noticed oscillation in temperature of motor coolant during driving. It raised slowly, approach to 90 oC, and afterwads went down to 40-50, up to 80-90 and again down. After a week it showed some temperature and after that went down on position without contact. During the last two weeks gauge is always on position like without contact (does not show anything). Should i suspect on thermostat, sensor, gauge, or something else. Where is sensor for coolant temperature? Thank you in advance. Dragan.

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Hi there:
DTC P1114 - Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage/IAT - B Circuit Low Input



The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant passage. Low coolant temperature produces a high resistance 100,000 ohms at -40 oC (-40 oF) while high temperature causes low resistance 70 ohms at 130 oC (266 oF).

OPERATION
The VCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will be high when the engine is cold. The voltage will be low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the VCM controls.

The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 9O oC (194 oF) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. When the VCM detects a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, the following Diagnostic Trouble Code (DTC) s will set.



Hope this helps.

Insufficient or weak coolant, bad thermostat (out of range), cooling fan not running or kicking into 2nd phase with A/C on, bad temperature sensor, bad temperature sending unit.(false guage reading).
Start by checking your coolant level and color (nice and green or orange? not rusty looking?) if rusty looking, flush coolant system and refill with recommended coolant type of 50/50 mixture.

Check specific gravity of coolant to see if the mixture is weak.

Verify cooling fan is kicking on after engine reaches operating temperature with engine idling.

Replace thermostat.

Measure resistance of temperature sensor. (should slowly raise as engine heats up)

Measure voltage at sending unit. (should slowly raise as engine heats up)

One of those should solve it, I always lean toward weak coolant and bad thermostat. I have seen bad water pumps do that too.

Mike

FOr 1993 Audi 90 2.8L SFI 6cyl the Coolant Temperature Sensor is located under hood, passenger side, rear engine area, mounted in cylinder head. Im sorry, but haven't some diagram.

Hope this helps (remember to rate this answer).

Check your coolant levels. If the temperature isn't much higher than normal, you may be fine, or you may have a Coolant Temperature Sensor going bad, and reporting the incorrect temperature. Even though the thermostat was replaced 8 months ago, it is possible it is already going bad again. I believe this is more of a Coolant Temp. Sensor fault though. The cooling fans are On when the AC is on. With the AC off, the cooling fans come on when the engine reaches a certain temperature, and cut off once the temperature is back in range. The Coolant Temperature sensor shouldn't cost much, and is easy to replace. I would start with that, top it off with coolant, and then maybe change the thermostat.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

The most likely problem you have is a partially stuck open cooling system thermostat. The coolant is constantly flowing through the radiator, so its not warming up as required. This in turn will increase your fuel consumption considerably. The alternator needs to be removed to gain access to the front of the engine block where the thermostat is located. Its a fiddly job, but straight forward for a competent mechanic. Another common fault also related with the cooling system is a faulty coolant temperature sender. Again a straight forward part to replace if needed.
Hope this helps you.

not easy.
back of the engine , below intake boot.
4 wire sensor.

16501/P0117 - Engine Coolant Temperature Sensor (G62): Signal too Low Possible Symptoms

• Difficulties with starting a cold engine.
• Starting the engine when engine is warmish or warm, idle rpm immediately is 1200 - 3000 rpm.
• RPM at idle is irregular.
• With all engine temperatures seldom idle rpm will vary between 900 - 1000 rpm.
• With engine warm (90 °C) the engine temperature suddenly drops (70 °C) and slowly comes back to 90 °C.
• Bad acceleration during warming up.
  • Diesel: an indication is extreme long time burning time of the glow indication light.

Possible Causes

• The electrical signal coming from G62 is too low
• Wiring and/or connections faulty (short circuit?)
• Engine Coolant Temperature Sensor (G62) faulty

Possible Solutions

• Check wiring and connections
• Check / Replace Engine Coolant Temperature Sensor (G62)

Special Notes

• In MY 1995-2002 (?) in Europe at VW-cars the G2/G62 had the bad reputation of breaking down often. The default G2/G62 is black and all replacements are green.

16502/P0118/000280 From Ross-Tech Wiki Jump to: navigation, search Contents [hide]

• 1 16502/P0118/000280 - Engine Coolant Temperature Sensor (G62): Signal too High
  • 1.1 Possible Symptoms
  • 1.2 Possible Causes
  • 1.3 Possible Solutions
  • 1.4 Special Notes

if (window.showTocToggle) { var tocShowText = "show"; var tocHideText = "hide"; showTocToggle(); } 16502/P0118/000280 - Engine Coolant Temperature Sensor (G62): Signal too High Possible Symptoms

• Difficulties with starting a cold engine.
• Starting the engine when engine is warmish or warm, idle rpm immediately is 1200 - 3000 rpm.
• RPM at idle is irregular.
• With all engine temperatures idle rpm will often vary between 900 - 1000 rpm.
• With engine warm (90 °C) the engine temperature suddenly drops (70 °C) and slowly comes back to 90 °C.
• Bad acceleration during warm-up.
• Diesel Engines: Glow plug indicator may be on for a longer than normal time or at ambient temperatures where it shouldn't come on at all.

Possible Causes

• The electrical signal coming from G62 is too low
• Wiring and/or connections faulty (short circuit?)
• Engine Coolant Temperature Sensor (G62) faulty

Possible Solutions

• Check wiring and connections
• Check / Replace Engine Coolant Temperature Sensor (G62)

Special Notes

• In many cars between MY 1995-2002 the G2/G62 had a bad reputation for failing often. The original G2/G62 sensor is black and the improved replacements are green.

Check the coolant temperature sensor housing in back of the engine. This is made out of plastic on some model years A4 and eventually leaks coolant.