Jaynen
Jaynen SuperDork
10/17/17 3:13 p.m.

So my car is throwing a code and has been for well over a year at this point. Its related to an auxiliary heater unit in the DEF tank. Of course you cannot replace this part only the tank itself which costs 1500-2k dollars for parts even tho its an easy DIY job to replace it. Does anyone know how you could find out what kind of resistance etc maybe the sensor is looking for and tap into it/send a false signal to make it go away?

RossD
RossD MegaDork
10/17/17 3:46 p.m.

Do you have any idea what the sensor does? Is it a temperature sensor? Are there safety concerns with spoofing it? If it's a simple thermal couple you can trick it with a resistor. Done. You just need to determine what you need, or grab a 1 meg pot and start turning until it goes off.

Dr. Hess
Dr. Hess MegaDork
10/17/17 3:47 p.m.

I take it that the existing heater unit is bad?  Can you get ahold of a good one, like at a parts store, and measure the resistance?  Or get a shop manual that has the spec in it?

GhiaMonster
GhiaMonster Reader
10/17/17 3:55 p.m.

Is the DEF tank electric or coolant heated?  Electric is an easy resistor. If it's an electric valve for a coolant loop that could be a bit more difficult.  Hopefully there isn't a rationality diagnostic that is looking for a temp rise after a certain amount of heater on-time that would set once the electrical error is cleared.

Keith Tanner
Keith Tanner MegaDork
10/17/17 4:01 p.m.

My favorite error code on my BMW is the "sensor plausibility" code. As in, "I'm getting a reading, but it seems off".

Some cars can be fooled with a simple resistor. Some are fiendishly good at determining that no, something really IS wrong. A shop manual may have the troubleshooting info you need, as Hess suggested. It could also be a wiring problem to the sensor.

93gsxturbo
93gsxturbo Dork
10/17/17 4:24 p.m.

You really need not just a schematic, but a theory of operation as well, IE what conditions have to be met for the code to get set.  Once you know that, at least you know what you are up against.

 

What sort of sweet vehicle is this?  Is it as easy as coding it out?  GM you can do it with EFI Live or HP Tuners, Euro stuff there are options as well just I am not as familiar with them.  

Stefan
Stefan MegaDork
10/17/17 4:26 p.m.

No wrecked cars you could get a spare sensor or tank from?

wearymicrobe
wearymicrobe UberDork
10/17/17 4:33 p.m.
Keith Tanner said:

My favorite error code on my BMW is the "sensor plausibility" code. As in, "I'm getting a reading, but it seems off".

Some cars can be fooled with a simple resistor. Some are fiendishly good at determining that no, something really IS wrong. A shop manual may have the troubleshooting info you need, as Hess suggested. It could also be a wiring problem to the sensor.

Add Chrylser P0601 to the list.

IE everything is working but the ECU cannot count and therefore you need to buy a new one. 

alfadriver
alfadriver MegaDork
10/17/17 4:46 p.m.
Keith Tanner said:

My favorite error code on my BMW is the "sensor plausibility" code. As in, "I'm getting a reading, but it seems off".

Some cars can be fooled with a simple resistor. Some are fiendishly good at determining that no, something really IS wrong. A shop manual may have the troubleshooting info you need, as Hess suggested. It could also be a wiring problem to the sensor.

So people know, flat line response is generally not real.  And is incredibly easy to detect.  

And given that spoofing signals is to be prevented- things like that happen.

One thing to note- IF there is a code for it, the manufacturer basically is saying that it's required to be running properly to meet the letter of the law.  

Jaynen
Jaynen SuperDork
10/17/17 5:16 p.m.

2011 Mercedes E-350 Bluetec has OM642 turbo diesel motor. Def tank is where the spare goes in the trunk

P20BD/P20BE is the code

P20BD P20BE

It's a secondary glow plug used to warm the tank itself if operating in sub 12 degree fahrenheit. There is additional heating elements which is why the code thrown is reductant heater control B or whatever

I did find this part number from Rock Auto and then looked it up but unsure if this is something else 

BOSCH F01C600241 Diesel Emissions Fluid Heater

Jaynen
Jaynen SuperDork
10/17/17 5:21 p.m.
Jaynen
Jaynen SuperDork
10/17/17 5:27 p.m.

I've had three different mechanics look at it all euro specialists one mercedes specifically and all have said that the parts only come as the whole tank however it does look like you can get piece 4 which looks like the heater unit for 980 which looks an awful lot like that Bosch unit I linked earlier 

Googling the part number off the site with that diagram shows it available at Parts Geek for 625

Parts Geek

 

Jaynen
Jaynen SuperDork
10/17/17 5:30 p.m.

Also I see something about 8yr 80,000 mile warranty on emissions stuff? Car has less than that and is 2011 wonder if it could apply? EDIT: doesnt look like it

underpowered
underpowered New Reader
10/17/17 6:40 p.m.

Yes, #4 is the heater and should be available separately from the tank.  

Jaynen
Jaynen SuperDork
10/17/17 6:42 p.m.

So I guess I could gamble on the 600 dollar part and try to replace it. 

RossD
RossD MegaDork
10/17/17 9:14 p.m.

Or take it out and try to fix it. I know, that's so 20th century. But if you figure it out, you will be an internet hero.

Jaynen
Jaynen SuperDork
10/17/17 9:17 p.m.

Always wanted to be a hero

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