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???

__________________
A Dalton

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

__________________
A Dalton

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?

__________________
A Dalton

Can I test the ECT sensor with a ohm meter?

No CE light on the instrument cluster.

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

__________________
A Dalton

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

__________________
A Dalton

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........................

__________________
A Dalton

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

__________________
A Dalton

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.