Service DEF system fault (new fault)

[Fern]

So I've got this message this morning and then its telling me I've one got x-number of miles until my speed is restricted. Plug in my scanner and came up with a few codes u02a2 and u02a3. Something about lost communication reductant quality module and lost communication with particulate matter sensor, Googled it and its seems to be with the sensors in the def tank. Where i live we've had some cold weather so don't know it thsts got anything or if i got bad def and it froze. But i also park o. The street so donot if someone put anything in the tank over night.
Not sure if anyone has come across this before or know how to fix it simply before i got to the dealership.

 

[mbarber84]

Both of those are “lost communication” codes. U02A2 is directed at the DEF quality sensor, which is part of the all-in-one unit inside your DEF tank. The U02A3 is directed at the Particulate Matter Sensor module. That would be the little control unit that the sensor plugs in to. Since you already have the countdown message on the evic, then that would indicate the code as tripped twice.

For “Lost communication” codes, I would start by checking battery voltage and battery connections, as well as grounds. If both are good, then I would suggest checking wiring connections under the truck. You may have some corrosion in connectors, or connections that are not fully seated. The harnesses that lead to both the def tank and the pm sensor module should be inspected to see if there’s a short to ground or other damage / disconnection. There have been a few reports where snow and ice had gotten up under the truck and had damaged some of the connections on the DEF system. That might be a place to start. If the truck continues to see the errors, and your countdown reaches zero, you will be limited to 5mph until either the onboard diagnostic sees the issue corrected or the pcm is cleared via a scan tool.

 

[Ronstar]

Q? here from a new member. It was mentioned “snow and ice” under the truck. I live in an area where both salt and Magnesium Chloride is used to deice the roadways. Is this problem going to effect this sensor? I’m perplexed as to why that sensor would be exterior and exposed to the elements.

 

[mbarber84]

@Ronstar salt and magnesium chloride should not be able to reach the DEF quality sensor as it is contained within the plastic DEF tank. However, the particulate matter sensor is one of several sensors that are threaded into the emissions system from the outside. The tips of these sensors sit within the exhaust pipe / chambers but the bodies are external, as is the wiring harness and control module. Theoretically they should be sealed like every other sensor on the truck, but as with anything else electronic the road salt and magnesium chloride are not friendly to it. This is why it is important to regularly wash the underside of the truck during the winter months to remove buildup of those compounds. It usually finds its way into sealed connectors no matter how good the seals are. It’s just the nature of those treatment compounds. No amount of seal will withstand those elements repeatedly.

 

[Ronstar]

Why do I think I’m going to have to go back school and get a degree in automotive mojo????? Thanks for the info!

 

[H3LZSN1P3R]

@Ronstar salt and magnesium chloride should not be able to reach the DEF quality sensor as it is contained within the plastic DEF tank. However, the particulate matter sensor is one of several sensors that are threaded into the emissions system from the outside. The tips of these sensors sit within the exhaust pipe / chambers but the bodies are external, as is the wiring harness and control module. Theoretically they should be sealed like every other sensor on the truck, but as with anything else electronic the road salt and magnesium chloride are not friendly to it. This is why it is important to regularly wash the underside of the truck during the winter months to remove buildup of those compounds. It usually finds its way into sealed connectors no matter how good the seals are. It’s just the nature of those treatment compounds. No amount of seal will withstand those elements repeatedly.

Annual undercoatings with stuff like fluid film or corrosion free keeps you from needing to wash the underside in the winter

 

[Fern]

Well i spent a few hours going over it today but still not luck. I disconnected the batterys and when over most of the plugs near the tank under the trunk. I also tryed to clear the codes too but my scan tool wont clear the ones marked permanent guess ill have to book it in to the dealer, unless anyone has anything else i could try?

 

[flan]

What years your truck? Follow the harness down the passenger side of the frame. It runs along the outside. Make sure it’s not pinched by any of the cab mounts or other exhaust mounts, particularly by the “B” post.

 

[Fern]

The truck it a 2019 3500.

Ive found the fuse keeps popping for the sensor f61 in the fuse box. I think there has to be a short somewhere, goong to have a look at it more closely Monday

 

[flan]

Here is a pic of where a harness can get pinched. It ends up between the bolt and cab. This picture is after the harness has been moved. Pic is pass side, midway under the cab.

 

[Fern]

So I've spent the last few days going through the harness under the truck like Flan pointed out but couldn't find anything pinch.

But what i did find out is there 12v to both sides of the fuse f61. So i started to unplug sensors on the def tank and testing at the fues box with a multimeter untill I'd stop getting 12vs. But sadly it never happened, so i think its something with the tipm. I pulled it out to look under it to see if maybe a mouse got underneath but nothing again.

 

[flan]

Check your owners manual, emission components have a longer warranty than the 36k bumper to bumper. Should be around 50k miles, up to 80k if in Cali.

 

[Fern]

Well the problem is back it was all good for a few weeks but the last good rain we had it came back. Took it to a friend that works at a local dealership and had one of the techs to scan it and tell me if its something that would be covered under my warranty. Sadly he doesn't think it will be, and he believes its the wiring harness somewhere under the truck he's had a few trucks they've had to replace the hole harness to fix similar issues. They told me to look in the same areas that ive already looked. i got a power probe short/open circuit finder and ive tracking it down to a spot on the harness on the driver's side of the block. It runs along the block and in between the fuel filter. It indicates theres a short just at the fuel filter housing.

So im going to fix it myself but if i cant dose anyone know if the dealership will do the recalls if ive deleted the def, i forgot to ask while i was there

​

 

[flan]

Well the problem is back it was all good for a few weeks but the last good rain we had it came back. Took it to a friend that works at a local dealership and had one of the techs to scan it and tell me if its something that would be covered under my warranty. Sadly he doesn't think it will be, and he believes its the wiring harness somewhere under the truck he's had a few trucks they've had to replace the hole harness to fix similar issues. They told me to look in the same areas that ive already looked. i got a power probe short/open circuit finder and ive tracking it down to a spot on the harness on the driver's side of the block. It runs along the block and in between the fuel filter. It indicates theres a short just at the fuel filter housing.

So im going to fix it myself but if i cant dose anyone know if the dealership will do the recalls if ive deleted the def, i forgot to ask while i was there

​

Recalls will still be done. When you find the fault be sure to follow back up with us here I’d love to know what you find.

 

[PRS]

Sorry I'm late to the show.
Here's a page from a 2020 warranty manual that says the harness is covered if you're under 50000 miles.

5. Emission Warranties Required
By Law
5.1. Federal Vehicle Emission Warranty -
6.7L Diesel Engine Equipped
A. Parts Covered For Five Years Or 50,000 Miles,
Whichever Occurs First
Diesel engine equipped vehicles are 2500 and
3500 models only.
Federal law requires FCA US LLC to warrant the
following emissions parts for five years or 50,000 miles,
whichever occurs first.
• Air system controls (including associated sensors)
• Charge Air Cooler (CAC) and associated plumbing
• Coolant temperature sensor
• Diesel Exhaust Fluid (DEF) system (includes tank,
sensors, valves, pump, doser, control module and heater)
• Engine speed, position sensor, and cam position sensor
• Exhaust system (includes all catalyst assemblies and
associated sensors)
• Electronic fuel injection system, including injectors
• Exhaust manifold
• Exhaust Gas Recirculation (EGR) assembly and control
system (includes EGR cooler, EGR bypass valve, EGR
valve, and associated sensors)
• Exhaust pipes (between exhaust manifold and last catalyst)
• Fuel pump, fuel lines and fuel injectors
• Intake manifold
• Mass air flow sensor
• On-board diagnostic-system components
• NOx sensors and associated modules
• Particulate matter sensor and associated modules
• Positive Crankcase Ventilation (PCV) valve or orifice*
• Powertrain Control Module (PCM)
• Throttle valve
• Transmission Control Module (TCM)
• Turbocharger assembly and turbocharger speed sensor
• Turbocharger compressor inlet air temperature/pressure
sensor
• Wiring harness circuits connected at both ends to emis-
sions warrantable components.
* Where parts are scheduled for replacement as required mainte-
nance, this warranty applies until the first scheduled maintenance
point listed in the Owner's Manual.

 

[Fern]

Sorry I'm late to the show.
Here's a page from a 2020 warranty manual that says the harness is covered if you're under 50000 miles.

5. Emission Warranties Required
By Law
5.1. Federal Vehicle Emission Warranty -
6.7L Diesel Engine Equipped
A. Parts Covered For Five Years Or 50,000 Miles,
Whichever Occurs First
Diesel engine equipped vehicles are 2500 and
3500 models only.
Federal law requires FCA US LLC to warrant the
following emissions parts for five years or 50,000 miles,
whichever occurs first.
• Air system controls (including associated sensors)
• Charge Air Cooler (CAC) and associated plumbing
• Coolant temperature sensor
• Diesel Exhaust Fluid (DEF) system (includes tank,
sensors, valves, pump, doser, control module and heater)
• Engine speed, position sensor, and cam position sensor
• Exhaust system (includes all catalyst assemblies and
associated sensors)
• Electronic fuel injection system, including injectors
• Exhaust manifold
• Exhaust Gas Recirculation (EGR) assembly and control
system (includes EGR cooler, EGR bypass valve, EGR
valve, and associated sensors)
• Exhaust pipes (between exhaust manifold and last catalyst)
• Fuel pump, fuel lines and fuel injectors
• Intake manifold
• Mass air flow sensor
• On-board diagnostic-system components
• NOx sensors and associated modules
• Particulate matter sensor and associated modules
• Positive Crankcase Ventilation (PCV) valve or orifice*
• Powertrain Control Module (PCM)
• Throttle valve
• Transmission Control Module (TCM)
• Turbocharger assembly and turbocharger speed sensor
• Turbocharger compressor inlet air temperature/pressure
sensor
• Wiring harness circuits connected at both ends to emis-
sions warrantable components.
* Where parts are scheduled for replacement as required mainte-
nance, this warranty applies until the first scheduled maintenance
point listed in the Owner's Manual.

Im out of the warranty for miles so it up to me to pay or fix it

 

[Fern]

I've spent the last few weeks digging through the harness, cutting it open. I bought a power probe short/open circuit finder to help me in the investigation. So i opened the harness every where its indicated the short where but nothing really stands out as a problem aera. But now its doing something funky the power probe keeps going from short to open circuit which means from 0 volts to 5 even seen a full 12volts at one point on the side of the fues that shouldn't have any voltage on it. All the relays in the tipm are clicking. The battery voltage is 12.38 not sure if thats an issue but ro be safe im going to put them on my charger and top them off.

 

[Fern]

So heres an update to the story, if anyone is still interested. So i got sick of chatting the harness issues and not finding an obvious issue, i ordered a new harness and had to wait as it was backorder. It took a few weeks for it to show up then two days for me to rip out the old one and install the new one.
Its now been 2 weeks with no real issues, the speed limit countdown popped up for few miles but when i stopped to check the codes it was gone and no codes where saved. But besides that I've been driving it daily with no issue so heres hoping its fixed.
Thanks for all the help

 

[flan]

So possibly a bad connector or wire broken internally in the harness it sounds like. What a ordeal. Good luck with the truck going forward, hopefully the issues are behind you.

 

[JamesL0109]

So heres an update to the story, if anyone is still interested. So i got sick of chatting the harness issues and not finding an obvious issue, i ordered a new harness and had to wait as it was backorder. It took a few weeks for it to show up then two days for me to rip out the old one and install the new one.
Its now been 2 weeks with no real issues, the speed limit countdown popped up for few miles but when i stopped to check the codes it was gone and no codes where saved. But besides that I've been driving it daily with no issue so heres hoping its fixed.
Thanks for all the help

Do you have a part number for that harness