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Topic: 2001 E-320 Station Wagon - Low Coolant Sensor Reply to Thread
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  Topic Review (Newest First)
05-23-2019 09:01 AM
mrboca Thanks for reporting back. Yes it is a bad design. More like an afterthought. Instead of providing individual sense circuits, they provided only one, and some voltage coded signal to determine the status of the levels. Probably some bug in the Instrument cluster firmware too. At least it is a relatively cheap fix.
05-23-2019 08:10 AM
hadam mrboca, some update. Yesterday I got the new Windshield Washer Fluid Reservoir Level Sensor. I remove the old washer fluid level sensor and install the new washer fluid level sensor.

After installation, I measured the resistance of new washer fluid level sensor and it was right on the money 176.8 Ohms.

After I connected the connector back to new washer fluid level sensor and started the car, no more coolant low level message. I connected my Autel diagnostic tool, No more codes, all cleared up.

So here the conclusion. Even though I was getting Coolant Expansion Tank Low Level Warning, and Code on reader as short on wiring of washer fluid level sensor/Expansion coolant tank level, the Problem was the Windshield Washer Fluid Reservoir Level Sensor.

It is bad design by Mercedes to display wrong message on IC when the problem was somewhere else. Anyhow the issue is now resolved.

Big thanks to all of you for your support. Special thanks to mrboca for info on all the resistance of individual level sensor and whole loop resistance.
05-18-2019 08:59 PM
hadam Witek_M, thank you for your recommendation. I will be careful to don't spread strands of test wire into IC plug.

I typically use tin wire for testing so strands of wire don't break and cause issues. I used these same tin wires on large expansion gas turbine in oil & Gas control system for testing.

Anyhow I will be careful.
05-18-2019 05:04 PM
Witek_M
Quote:
Originally Posted by hadam View Post
mrboca, some update. Today I removed the IC and measured the whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor. The Reading I got of 154.8 Ohms. Way lower then I expected, but match what you have told me.

My reading of Windshield washer fluid reservoir level = 33.6 ohms

whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor = 154.8 ohms

It means Expansion coolant tank level sensor 154.8 ohms Minus 33.6 ohms = 121 ohms, which is good.

So my problem is the Windshield washer fluid reservoir level sensor, which suppose to be 145-185 ohms and I am getting only 33.6 ohms.

Thank you mrboca, I will get Windshield washer fluid reservoir level sensor for $16.

Below are some photos from today.
It is great that you were able to get that measurement from IC connector. In the future avoid poking into connector from the front unless you have correct pins to do so. Spreading female connector may lead to never ending errors in that circuit.
05-18-2019 04:13 PM
hadam mrboca, some update. Today I removed the IC and measured the whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor. The Reading I got of 154.8 Ohms. Way lower then I expected, but match what you have told me.

My reading of Windshield washer fluid reservoir level = 33.6 ohms

whole loop resistance across Expansion coolant tank level sensor and Windshield washer fluid reservoir level sensor = 154.8 ohms

It means Expansion coolant tank level sensor 154.8 ohms Minus 33.6 ohms = 121 ohms, which is good.

So my problem is the Windshield washer fluid reservoir level sensor, which suppose to be 145-185 ohms and I am getting only 33.6 ohms.

Thank you mrboca, I will get Windshield washer fluid reservoir level sensor for $16.

Below are some photos from today.
05-14-2019 09:50 AM
hadam mrboca, Thank you so much for such a good info on IC and resistance of individual level sensors and over all loop resistance.

I will remove the IC this weekend and will give you update. I believe I have issue with windshield washer level sensor and NOT Expansion Coolant Tank level sensor.

Again many thanks for your time and support.
05-14-2019 07:53 AM
mrboca Yeah, follow the procedure, starting with item 3.0 in the attached link.

STAR TekInfo
05-14-2019 07:46 AM
hadam mrboca, thanks for your reply. As of today, I have not seen any more message on IC for Low coolant level.

I will check the circuit from IC side by removing IC and then taking Ohms reading from Electric bracket B just to see what will be the total loop resistance that goes through coolant lever sensor and washer fluid level sensor.

It is quite difficult to read resistance of Expansion tank coolant level sensor, the connector are way in and unless you remove the air box and then expansion tank, there is no simple way to read the resistance. I will read the resistance of Coolant level sensor via IC electrical connector plus washer fluid level sensor connector per attached IC diagram.

I will keep you posted.

The Washer fluid level sensor is quite low cost, it is sold for only $16.

https://www.ebay.com/itm/153337606533?ul_noapp=true
05-13-2019 11:48 AM
mrboca You probably had an intermittent short on the line which caused the IC to read a short.

I do not think the IC has the capability to display both coolant and the washer fluid low message in case of a short detection on the line, so it displays the washer fluid low message by default, with an error code.

It is also important to note when the actual test is done. In my experience, the washer fluid low message pops up when you turn the contact, and I think it would give implausible value if the test is done when the car is moving due to fluid sloshing in the container. So if you had the fault cleared and then pulled the connector while the key is in position 2, it may not register.
05-13-2019 10:58 AM
hadam
Quote:
Originally Posted by mrboca View Post
Bad reading. You should get between 145 to 185 ohms at the sensor connector with the cable pulled off for a full tank.

The measurement towards the harness connector, 647 ohms is meaningless, especially if the ignition is on (it carries sense power from the cluster).

You always must make these measurements with the ignition OFF.

You may have some stray resistance on the harness to ground.

Typically you need to remove the connector at the back of the instrument cluster and make a measurement from that connector.
mrboca, thanks. Since I have cleared the code, all is good, I am not getting any messages on Instrument cluster.

I believe the way system is design is that when IC sees the low resistance in the system, it create code B112B and display on IC the message Coolant Low Level. So look like the logic in instrument cluster is that on low resistance or Mercedes call it short circuit, it will display the message Coolant Level Low.

One other observation is that when I removed the connector from washer fluid level sensor, I was getting no message. It means if there is open circuit, the instrument cluster doesn't display any messages.

Anyhow, all the connectors are connected as normal for washer fluid level sensor and coolant expansion tank level sensor. I have been driving the car and no more message.

When I get some time, I am just going to remove the instrument cluster and quickly read the resistance on IC connector IB terminals 4 and 12. This will give me full loop resistance when Coolant Expansion tank is full and windshield washer reservoir is full also. I will keep you posted.
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