[dixy2k]

First of all I cannot take any credit for this idea. It belongs to someone else who shall remain nameless in an undisclosed location.

I talked to him about taking the DEF tank out in order to fix my issue with the SES. It only took him 4.25 seconds to to think and tell me there is a better way, instead of dropping the mufflers, and DEF tank.

He came up with 2 other ways to add the resistor.
1) the old way, of course.
2) wire at the ECU location
3) wire loom behind the bumper, passenger side


I will attach a wiring diagram for this job.
First page, right in the middle of the page, you can see the 3 methods.

On top, the ECU location, middle behind the bumper and bottom tank.

Those people with a lot more electrical knowledge can probably make a lot more sense out of this diagram.


Page two explains how the level sensor works. Pretty self evident on the right side of the page.

Third page... I have no clue.

[335dsleeper]

What size resistor? If he doesn't know, you'll have to measure the sensors range with a multimeter. If he knows the resistor size, please post. That'll save a lot of time.

[glitdi]

Measure voltage on pin one, right side like you mentioned. If its 12v it will be slightly easier..It states reference voltage, that may be 5v which means its can bussed based which will be a little more difficult to fool. I am of the opinion that the voltage is passed through the urea and picked up at the different levels so adding one resistor my not be enough,it will need to see voltage at least at two levels to think it is full. Example to get a full tank the ecu needs to see voltage on all three pins, just jumping the high level pin probably wont work.. You may need to make up a jump wire into pin two and pin three you don't have to jump pin 4 since a mid level fooling of the tank will be acceptable to keep the low level light away.
So basically the urea acts as a resistor, you are going to have to measure voltage in vs voltage out at the different levels and then some good old ohms law to calculate your resistance..(correction, sorry it was a late night I am over complicating things a bit... Disconect harness, measure resistance between the various pins, so pin 1 to 2, 1 to 3, 1 to 4 with def at at least mid level and voila! Disconect the harness, jump from pin 1 to 2 and three and parallel with there resistors and that should fool her.The resistance should be fairly close if not the same, keep in mind each level is a longer piece of metal to pick up the levels so there will be a slight variation in resistance between them..If you need proper german pins to pin the harness let me know I can walk you through it or build you a harness once I know what I am working with..Will need a picture of the pins to make a jump harness.) I think thats all.

[glitdi]

Also if someone has a clearer picture of the 3rd page I can take a look, the copy is to fuzzy for me to make sense of it...

[terry335d]

The resistor voltage value is in another thread on this forum. I don't have time to look right now.

[dixy2k]

10k thermistor

[335dsleeper]

Originally Posted by dixy2k

10k thermistor

Thanks. You sure this will work for the level sensor?

[dixy2k]

One was sent to me by a member here who did it at the tank. It takes a lot of time to drop the mufflers, and the tank, go through the trunk and dig in to attache the thermistor on that one wire.

If you do it in a different way, it may just be easily reversible, in the event you want to sell the car and not have some dark cloud hanging over you all the time.

[335dsleeper]

Originally Posted by dixy2k

One was sent to me by a member here who did it at the tank. It takes a lot of time to drop the mufflers, and the tank, go through the trunk and dig in to attache the thermistor on that one wire.

If you do it in a different way, it may just be easily reversible, in the event you want to sell the car and not have some dark cloud hanging over you all the time.

Didn't he trick the temp sensor? Or did he use it on the level sensor?

[Yozh]

He did it on a temp sensor.

[335dlci]

I'm kicking my self in the rear for not keeping an urea tank I replaced at work that had both faults and could have figured out the level sensor!! Damn

[335dsleeper]

^ Thats what i thought. Does anyone know if this will work for the level sensor?

[CvilleBill]

Has anyone tried Bob's fuse pull? "(STILL BETA TESTING) Remove fuses leading to the tank mixture sensor, heater and level sensor.

You need to remove 3 fuses that control the sensors in the tank.
.
35 & 58 from the fuse panel inside the car

05, its located inside the ebox in the little white fuse holder."

[QUIKDZL]

The 10k thermistor I used was not to trick the ECU, but to replace the failed OEM thermistor and keep the SCR system functional. If you are looking to delete the SCR system (or remove it) and trick the ECU into thinking it is still there, you would need to install a 10k thermistor somewhere in the wiring harness to replace the OEM SCR temperature sensor. This would be required as opposed to just installing a 10k resistor because the ECU compares urea temperature to ambient for a plausibility check.

As for the level sensors, the reference/low/mid/high level probes simply complete a circuit to tell the ECU where the level is. The ECU does not need a resistance value to measure the urea depth. Simply short the reference wire to the low and mid probe wires so the ECU thinks the active tank is somewhere between half full and completely full. This should do the trick.

[Yozh]

Originally Posted by 335dsleeper

^ Thats what i thought. Does anyone know if this will work for the level sensor?

I thought you are tuned and do not need to worry about the urea or the tank sensors?

[335dsleeper]

Originally Posted by Yozh

I thought you are tuned and do not need to worry about the urea or the tank sensors?

Well, it's a work in progress. I had a no start recently. Had to plug the tank back in. I have 900 miles remaining so, we'll see if it's good now.

[Yozh]

Originally Posted by 335dsleeper

Well, it's a work in progress. I had a no start recently. Had to plug the tank back in. I have 900 miles remaining so, we'll see if it's good now.

I see. Hope you guys will figure it out soon. Rather unfortunate to be tuned and still lug that tank half full of weight ballast that you do not really need. Hopefully, you will be able to take the tank out together with all of the transfer pump module and yank the NOx sensors off the exhaust as well. These cars are full of tricks to tune out.

PS: really hope you are not spraying urea...

[335dsleeper]

Originally Posted by Yozh

I see. Hope you guys will figure it out soon. Rather unfortunate to be tuned and still lug that tank half full of weight ballast that you do not really need. Hopefully, you will be able to take the tank out together with all of the transfer pump module and yank the NOx sensors off the exhaust as well. These cars are full of tricks to tune out.

PS: really hope you are not spraying urea...

My tank and pump are completely removed. I pulled the fuses this time, hopefully it stops the countdown.

[335D Alpha Pappa]

Originally Posted by QUIKDZL

As for the level sensors, the reference/low/mid/high level probes simply complete a circuit to tell the ECU where the level is. The ECU does not need a resistance value to measure the urea depth. Simply short the reference wire to the low and mid probe wires so the ECU thinks the active tank is somewhere between half full and completely full. This should do the trick.

This was one of the future items I planned to look into.

The level sensor does need a resistive element between the sensor lines. It uses the conductivity of the urea to determine the level. A lower resistance between the electrodes indicates a full tank because the urea covers the entire electrode. A short would indicate a fault.

I think that using the conductivity of the urea is how BMW checks to see if it is urea and not water.

[QUIKDZL]

You may be right, Pappa, but I'm still of the opinion that level is determined to be empty/low/medium/full simply by continuity between rods, and that urea quality is determined by NOx sensor readings. But I've been wrong before...

[dreyo27]

So did anyone figure out a way to defeat/Bypass/replace the level sensor?

I had both level and temperature sensor error.

Replaced the 10k thermoresistor in tank and temperature error is gone.

The level sensor error is still there

[Built4Sin]

Go to bmw and get it fixed for free with the DEF warranty extension.