[Billybob#10]

I HAVE A 2014 DURAMAX WITH 31,000 MILES ON IT.
THE CODE SHOWED UP , P20B9 ON MY WAY TO WORK, STATING 99 MILES TILL SPEED LIMITED TO 65 MPH, THEN, 70 MILES TILL SPEED LIMITED TO 55 MPH, ACCORDING TO THE #'S IN 40 MILES I WILL BE LIMITED TO 55 MPH. I AM PARKED BOUT 150 MILES FROM HOME . NEW REDUCTANT HEATER JUST ARRIVED AT HOME.

QUESTION # 1 IF I REMOVE THE BATTERY CABLES. WILL THE COMPUTER RESET AND TAKE THE SPEED LIMIT OFF, W?
QUESTION #2. WHERE EXACTLY DID YOU PLACE THE RESISTER IN THE CIRCUIT, IN LINE OR ACCROSS BOTH THE WIRES ? PIC'S?
QUESTION #3 ARE THE WIRES ACCESABLE WITHOUT REMOVING THE TANK?

THANKS
BILL

 

[Buckslayer88]

So I just got the same code, did you cut the two wires and wire them both to the resister? Or just wired it in series with one of the wires? Can you take a pic please.

Easiest way is to lower tank a bit to find the harness going to tank heater on top of tank. You find to wires coming out of the main def system harness leading to a two wire plug on top of tank. From the plug the wires continue to the sending unit. Unplug the plug and check resistance, if unusally high or an open is found it is bad. Then cut wires as close to sending unit to keep as much wire as possible to solder your resistor on. The heater is essentially a series circuit so by connecting both wires to your resistor you are closing the loop and there for the computer will see the resistance.

 

[Buckslayer88]

Is a scanner tool required?

Yes you need an autel or snap on, etc than can run the reductant heater test which is the only way that i know can clear the message and limp mode

 

[Buckslayer88]

I HAVE A 2014 DURAMAX WITH 31,000 MILES ON IT.
THE CODE SHOWED UP , P20B9 ON MY WAY TO WORK, STATING 99 MILES TILL SPEED LIMITED TO 65 MPH, THEN, 70 MILES TILL SPEED LIMITED TO 55 MPH, ACCORDING TO THE #'S IN 40 MILES I WILL BE LIMITED TO 55 MPH. I AM PARKED BOUT 150 MILES FROM HOME . NEW REDUCTANT HEATER JUST ARRIVED AT HOME.

QUESTION # 1 IF I REMOVE THE BATTERY CABLES. WILL THE COMPUTER RESET AND TAKE THE SPEED LIMIT OFF, W?
QUESTION #2. WHERE EXACTLY DID YOU PLACE THE RESISTER IN THE CIRCUIT, IN LINE OR ACCROSS BOTH THE WIRES ? PIC'S?
QUESTION #3 ARE THE WIRES ACCESABLE WITHOUT REMOVING THE TANK?

THANKS
BILL

You cannot clear message by disconnecting battery, has to be done by diagnostic tool.

You are eliminating the heater out of the equation so you have the wires as close to heater as possible and connecting resistor in series (in place of heater). I was able to access without totally dropping tank. Loosened straps and bejng supporting by floorjack just lowered it a bit for access. Shouldnt take any longer than an hour to accomplish the work. Sorry dont have pics.

 

[Billybob#10]

Thank you

 

[BBE]

This is an old topic I know...but stupid question here. What if you DO live in a cold climate? Will this fix still work as basically a hard wired def bypass/delete? I'm ok with the def fluid freezing and not actually being able to be used. Don't care...just want the error message to go away and want my truck back out of limp mode.

 

[duecedriver]

OK, Message on dash says to service DEF system, 147 kilometers until reduced max speed 105 km/h. Code P20b9 shows up on the scanner.
I'm 275 kms from home. So finished the trip, in limp mode and took it to the dealer who informed me that my extended warranty does not cover the DEF system PERIOD! And the repair will be minimum $1000, or they could do a single stage delete for $1500 which they said wouldn't affect the rest of my extended warranty. Not being naive, I told them I would get it fixed elsewhere. Took it over to my favorite mechanic and he fixed it by installing a light bulb in place of the heater circuit, clearing the code and requesting a DEF system diagnostic on his scan tool. Total parts about $12 and an hour labour. This service got me back on the road where the truck needs to be to make any money, saved me a grand which I can put towards the delete when the ext warranty does expire. (15000 kms):grin2:

but if i read this right.. you light bulb provides the load feedback to the ECM of what the heater would do.. what happens when your DEF is frozen and the vehicle cant keep NOX within limits.. won't that throw codes that will put you in limp mode?

 

[BBE]

but if i read this right.. you light bulb provides the load feedback to the ECM of what the heater would do.. what happens when your DEF is frozen and the vehicle cant keep NOX within limits.. won't that throw codes that will put you in limp mode?

I was thinking my understanding is that there is a def sensor that is reading the temperature. And actually disables the entire def system if the temperature is low enough that it's frozen. The heater turns on when this happens, and is on for 270 minutes, and the def system is enabled again once the sensor reads that there is no longer any danger of the fluid being frozen.

So basically by jumping the heater with a resistor, it gives the illusion that the heater is working fine, but the temperature never gets above freezing per the def sensor. So in theory, the entire def system just stays disabled because of this. So basically it's just like the heater is on but can't keep up so the def system stays off.

 

[duecedriver]

I was thinking my understanding is that there is a def sensor that is reading the temperature. And actually disables the entire def system if the temperature is low enough that it's frozen. The heater turns on when this happens, and is on for 270 minutes, and the def system is enabled again once the sensor reads that there is no longer any danger of the fluid being frozen.

So basically by jumping the heater with a resistor, it gives the illusion that the heater is working fine, but the temperature never gets above freezing per the def sensor. So in theory, the entire def system just stays disabled because of this. So basically it's just like the heater is on but can't keep up so the def system stays off.

I posted a pdf on how the reduction system works in the l5p a while back. True that the system disables the def while defrosting but it says delays. I don’t think it’s indefinite. Further if the def is not active. Nox levels will not come down because scr won’t function correctly so after some time you will likely throw codes for nox

 

[Sweat72]

I was thinking my understanding is that there is a def sensor that is reading the temperature. And actually disables the entire def system if the temperature is low enough that it's frozen. The heater turns on when this happens, and is on for 270 minutes, and the def system is enabled again once the sensor reads that there is no longer any danger of the fluid being frozen.

So basically by jumping the heater with a resistor, it gives the illusion that the heater is working fine, but the temperature never gets above freezing per the def sensor. So in theory, the entire def system just stays disabled because of this. So basically it's just like the heater is on but can't keep up so the def system stays off.

I posted a pdf on how the reduction system works in the l5p a while back. True that the system disables the def while defrosting but it says delays. I don’t think it’s indefinite. Further if the def is not active. Nox levels will not come down because scr won’t function correctly so after some time you will likely throw codes for nox

I’m new here And just figuring this forum out ,definitely a Lotta good helpful information I just replaced the DEF heater in my 2016 2500 it was code p2033 and p21DD. I have a friend’s scan tool but I cannot get the codes to clear. Any advice would be appreciated? I still have a message on the DIC 20 miles until reduced speed to 55

 

[trvslightfoot1]

Absolutely F-ing brilliant!! That is by far the best solution that I have every heard of for this complete DEF nightmare. I have deleted plenty of trucks in the past but not everyone can afford to delete, so this is an absolute genius solution!!

 

[trvslightfoot1]

Can I ask what will happen to the filter when you drive the truck for some time and the spot builds up? Isn’t the reductant system specifically designed to help bake the soot out?
I absolutely love the idea of this trick, but I’m not sure if it will last very long before the soot levels are through the roof. What to do then?

 

[Ron Nielson]

The reductant system is designed to remove contaminants in the exhaust gas, does not have anything to do with the soot caught by the DPF.

 

[Timmyb22]

You cannot clear message by disconnecting battery, has to be done by diagnostic tool.

You are eliminating the heater out of the equation so you have the wires as close to heater as possible and connecting resistor in series (in place of heater). I was able to access without totally dropping tank. Loosened straps and bejng supporting by floorjack just lowered it a bit for access. Shouldnt take any longer than an hour to accomplish the work. Sorry dont have pics.

Hey guys so I was able to do the bypass on my 2018 l5P as well only issue I’m having is clearing the codes off the instrument panel/dash. Hooked up to scanner and no codes show up but I still have the message on the dash that I’ll be limited to 65mph in so an so miles. Any help appreciated I just need to dash codes to clear so I can do some exthaust work

 

[Ottowood]

You have to run a system tamper test with a scan tool.. The ECM needs to see everything is working properly and then the message will clear..
You can drive it and it will run a self test also.. The message will not clear if the ECM sees a problem.