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2013 F350 lariat supercab shortbed in 2 tone
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Discussion Starter · #1 ·
so a few weeks ago i got the p20ba code and summarily replaced the def tank heater, put it all back together, and when doing so let the tank slip, so i ended up needing a new pump since the damn plastic fitting for the reductant fluid hose broke. got the new pump in, put everything back together only to find new codes, including p204c, the others i fixed. but this damned p204c(reductants pressure sensor circuit low) is killing me. I've tested every single pin in the def tank harness from end to end, and to while plugged in to the pcm wiring harness. there are no continuity failures anywhere. yet this code is constantly coming back within 2 or 3 miles. i even ran the def tank replacement re-learn program on for scan to no avail. the problem I'm seeing is that the pcm isn't allowing the def pump to turn on, which is leading to this code because the sensor isn't reading pressure. but on the other hand this issue appears to stem from a poor or bad ground somewhere( the ground strap from body to frame under front passenger door is junk). so my curiosity is peaked, and now I'm wondering if the limp mode, which until today was the 50 miles till 50 mph speed limit warning and is now the 50 mph speed limit, is causing the pump to stay off. Or if this could be a bad NOx sensor or high NOx reading that's causing the limp mode, even possibly as far as an egr issue?. i also read an account that one owner had a similar issue due to a bad maf sensor, both of which could ultimately cause scr system issues. I don't want to do a forced regen in the def pump isn't going to even be pumping def.

what's your thoughts? this was my first time working on a 6.7 def system, but defiantly not my first time working on scr systems in big rigs, or other diesel engines since I'm a mechanic. I've never come across something like this and I'm now wondering if I'm simply not overthinking this or overlooking something simple. thanks!
 

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So the P204C code is new, appearing right after "dropping" the tank? If this is the case then I would test the circuits for the sensor and the pump thoroughly suspecting harness damage. If the harness was connected when the tank slipped you could have pulled a pin out or broke a wire in one of the connectors. What diagnostic tool are you using?

The reality is if the sensor does not show a pressure rise when the pump is commanded on the SCR system is disabled. Same thing happens when the pump fails to build pressure. In this scenario you have a circuit code for the sensor.
 

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2013 F350 lariat supercab shortbed in 2 tone
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Discussion Starter · #3 ·
So the P204C code is new, appearing right after "dropping" the tank? If this is the case then I would test the circuits for the sensor and the pump thoroughly suspecting harness damage. If the harness was connected when the tank slipped you could have pulled a pin out or broke a wire in one of the connectors. What diagnostic tool are you using?

The reality is if the sensor does not show a pressure rise when the pump is commanded on the SCR system is disabled. Same thing happens when the pump fails to build pressure. In this scenario you have a circuit code for the sensor.
I tested every single pin in the wiring harness, from end to end and while pugged in to the pcm harness. there's no wiring issues. same for the pump, every pin showed continuity. the pump works, that was tested with a 12v jumper pack and wires. when i clear the dtc log, the cel light stays off until the next restart. thee oscilloscope/ dashboard on my program shows that the pump, sensor, and tank pressure sensor are showing zero values. mind you, everything functions outside of the truck, but not plugged in. other than a faulty pcm, this cascading failure makes no sense. it started as a p20ba code, so i replaced the heater unit, then got the p208a, the pump needed replacement, mind you that the pump that threw the p208a was functioning, it was pumping def right after i dropped the tank and the plastic nipple broke off. put the new pump in, and here we are. i have tried 2 brand new pumps suspecting that the sensor or a plug was faulty on the first new one, neither have pumped def, and both left me with p204c.

im using my scan tool and Forscan. mostly forscan since my laptop has the bigger screen.
 

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Silly question: Did you prime the pumps before installing them? (have to ask)

Second silly question: Did you notice the new Heater/sender comes with the large pump seal installed but not the small? Did you double seal the pump? (have to ask)
 

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2013 F350 lariat supercab shortbed in 2 tone
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Discussion Starter · #5 ·
Silly question: Did you prime the pumps before installing them? (have to ask)

Second silly question: Did you notice the new Heater/sender comes with the large pump seal installed but not the small? Did you double seal the pump? (have to ask)
yes, both pumps primed, probably excessively but i wanted to make sure i got as much def in as i could. there were no seals in the heater unit. hell i even played with pulling def up the suction pipe with the syringe and changing the o-ring and seal out.

EPIPHANY MOMENT: i wonder is the damned pickup tube isn't plugged, I didn't see any shipping plugs on anything when I opened it, but I think ill be pulling it apart again tomorrow to check.
 

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There are no shipping plugs. EVERY heater/sender assembly I have ever replaced has had the large o-ring installed in the top.
 

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Discussion Starter · #7 ·
There are no shipping plugs. EVERY heater/sender assembly I have ever replaced has had the large o-ring installed in the top.
the one i got had thee o-ring in a bag with the smaller one and the screws. truck is now about to go into idle only, idc. im picking up an ezlynk tomorow after work. know any good tunes for these trucks that are not emmisions in tact?
 

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Discussion Starter · #9 ·
What ever came of this? I’m having the same 204C code after changing the heater and also the pump/sender.
long story short, i removed the aftertreatment bullshit, the repairs would've cost double the cost for me to do a little welding and pay for the exlynk and tunes. best i can say to you is to remove the pump, reprime it multiple times, possibly replace the reductant hose to the def injector, and hope its not a pcm failure. I did see service bulletins for the issue but didn't want to take the chance of being stuck with a 5k dollar bill if the dealer refused to acknowledge it.
since your probably curious, the factory pipe is 3.5 inch, remove all dpf sensor plugs, unbolt the front exhaust flange, and the coupler under the cab, drop dpf, measure for your cuts to replace that amount of pipe, cut off rear dpf flange to weld onto replacement pipe, cut front pip off dpf were it straightness out to go straight back, tunes, and actually have throttle response and power. 18 mpg on a 400 mile trip, sounds awesome, and the power is unbelievable.
 
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