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2024 Laramie 2500 6.7 DEF Gauge Zero / Check Engine Light

jetspeed24

jetspeed24

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First post - appreciate any help. Bought 5 days ago with 18,000 miles. 300 freeway miles home, ran great. Regen cleared DPF from 30% to zero. DEF gauge read just over 3/4 and appeared to be very slowly coming down. All seemed good. Today I have check engine light and DEF gauge reads zero. Several engine start/stops did not clear. Added 2 gallons to DEF tank until it overflowed. No impact. Not in limp mode. Truck was from Utah, now on the left coast so truck has not been anywhere near freezing for a while.

I have not pulled check engine codes yet.

Thanks again,
Dave
 
jetspeed24 said:
First post - appreciate any help. Bought 5 days ago with 18,000 miles. 300 freeway miles home, ran great. Regen cleared DPF from 30% to zero. DEF gauge read just over 3/4 and appeared to be very slowly coming down. All seemed good. Today I have check engine light and DEF gauge reads zero. Several engine start/stops did not clear. Added 2 gallons to DEF tank until it overflowed. No impact. Not in limp mode. Truck was from Utah, now on the left coast so truck has not been anywhere near freezing for a while.

I have not pulled check engine codes yet.

Thanks again,
Dave
Click to expand...
Gotta pull the codes. Without code you have no way of knowing what is setting the CEL.
 
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Could be crystallization on the level sensor, could be a bad sender, tough to say. Filling until overflowing has been known to also cause issue, it takes up the needed air space the level sensor needs to correctly judge the amount in the tank.
On that note check the harness from the sending unit to the cab. I believe the wiring harness right behind the wheel well plastic guard for the driver side front tire can get caught under the cab mount and pinch wires. Also on the passenger side roughly below the b pillar wiring has an opportunity to pinch.
 
Update: thanks for the replies. I put it on a trickle charger overnight, started it this morning, DEF still zero, CEL on. After a few minutes at idle the DEF gauge came alive, went back to 3/4 full where it was before, then slowly climbed to full which is correct. OBD showed P203B which I cleared. I will check the harness.

Any other recommendations based on the code?

Thanks again,
Dave
 
Filling the DEF tank to the point it overflowed may cause you additional problems. These tanks are designed so that when filled to their rated capacity, there’s still a significant amount of air gap between the top of the fluid and the roof of the tank. When it’s filled to the point it spills out of the filler neck, you’ve effectively removed that gap of air. The air gap is necessary for the ultrasonic level sensor to accurately read the fluid level. It works similar in principle to sonar echo on a ship or submarine. No air gap means that the “ping” won’t return correctly to the level sensor and it’ll trip a “no echo” fault, resulting in additional codes. If P203B was present before you filled the tank too full, then you have a level sensor short, or a wiring issue as suggested previously. Either way, it’s a brand new truck so I would let warranty cover it.

Have you run the DEF tank very low at any point in the past? Or recently?
 
mbarber84 said:
Filling the DEF tank to the point it overflowed may cause you additional problems. These tanks are designed so that when filled to their rated capacity, there’s still a significant amount of air gap between the top of the fluid and the roof of the tank. When it’s filled to the point it spills out of the filler neck, you’ve effectively removed that gap of air. The air gap is necessary for the ultrasonic level sensor to accurately read the fluid level. It works similar in principle to sonar echo on a ship or submarine. No air gap means that the “ping” won’t return correctly to the level sensor and it’ll trip a “no echo” fault, resulting in additional codes. If P203B was present before you filled the tank too full, then you have a level sensor short, or a wiring issue as suggested previously. Either way, it’s a brand new truck so I would let warranty cover it.

Have you run the DEF tank very low at any point in the past? Or recently?
Click to expand...
Very helpful info, thank you. I've only put 500 miles on the truck so DEF level has not been below half full for me. I will see about draining a little to create an air gap.
 
I would make an appointment with the dealer and tell them that the gauge dropped to zero and when you tried to add DEF it was over full. If it’s a 24 model, I would let them spank the monkey and tell them what happened. NEVER delete dtc’s out of these trucks if you have a warranty and plan on taking it to the dealer. For them No code = No problem.
 
Popped the injector to confirm no crystallization. I think I just need the gasket. Is this pump cover gap normal?

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2 drive cycles, all good. Now DEF gauge just dropped back to zero and CEL is on. Not seeing the restricted mileage message, wondering how likely that is to appear. Supposed to head to the mountains tomorrow.
 
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