Location of engine coolant temperature sensor
 

I have a 1993 300E with 104 engine. This is the same engine as the 94-5 320E.

Can someone tell me where the engine coolant temperature sensor is located. Is it east to get to? If anyone can provide a picture, that would be great.

Does the sensor connect to the engine wiring harness? How many prongs are on that connector?

There are 3 coolant temp sensors ..which one are you concerned with???

The ECT that I am looking for is the one that causes 2 flashes "ECT sensor" on the code reader while testing Pin 8 ECU.

Side mounted sensor under thermo housing

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2AO123CS42DW029DXP&year=1993&make=MB&model=300-E-004&category=C&part=Water+Temp.+Sensor

Thanks, Arthur.

If this ECT sensor is bad, would it cause cold start problems and bad gas mileage.

Is the Pin to test emissions on Pin 6?

Does car have a CE light?

Can I test the ECT sensor with a ohm meter?

No CE light on the instrument cluster.

Yes , it is a Negative thermistor.....

Then the car is FED version and has no Emmissions Module [ N/59]

I am planning to change the ECT sensor but in the meantime should I do the following:

a) disconnect the ECT sensor (infinite resistance)

b) disconnect the ECT sensor and bridge the 2 female connectors on the wiring harness (0 resistance)

c) leave the ECT sensor connected to the wiring harness


This is what I am currently experiencing:

In the morning, car needs about 4 or 7 cranks with engine stumbling and dying before the engine warms up enough. After that car runs well.

In the after noon, car needs about 2 cranks before the car starts.

When the engine is warmed up, car runs suprising well.

Unplug the sensor, clean the terminals , replug it, clear the code and run it. See if code returns.
I would also ohm it to make sure it is not Open.

..and check the insulation on the plug........................

Good suggestion. I will try that tomorrow.

On this car, the only pins that can be read using the code reader is 8, 14. Does pin 6 test for anything? I got 1 flash.

SRS -N/2 module
1 flash is no codes

Thanks, Arthur for the tips.

I tested the ECT sensor and it apprears to be good (250 ohms at 60 degrees).
The connector has 3 holes and only 2 holes with wires connected to it. The 2 wired holes tested negative for a short so insulation must still be good for now.

My problem was that the 2 wired holes were not connected to the pins on the sensor. It is easy to line up the wrong holes to the pins. I reattached the sensor correctly and reset pin 8 with the code reader. Hopefully, tomorrow the cold start and stumbling go away.

I spoke to soom. Problem did not go away. When testing pin 8 with the code reader today, I still get 2 blinks which indicates a problem with the ECT sensor.

The ECT tested fine. 250 ohms at 85 C and 1200 ohms at 25 C. I cleaned the connctors and pins.

Does anyone have a wiring diagram and let me know what is conncted between ECU and ECT sensor? Does anyone know what triggers a ECT sensor fault. Does the ECU compare the ECT sensor with another component to determine if the ECT sensor is good?

ECT sensor B11/3 is wired directly back to HFM/SFI N3/4 modules pins #28 & #36.
Sensor is monitored for short or open circuit.
R value comparison was not until '95 E320 version.
Suspect is harness.

Arthur, many thanks.

Cold start problem resolved. I opened the wiring sheathing to the ECT sensor and insulation toward the end of the connectors was disintegrated and bare. I taped up the bare wires and the car now starts fine.

So if anyone has unexplained codes and the sensors are fine, cut open the wiring harness and check it.

You need a Wire Harness.