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Discussion Starter #1
I'm having a defuel issue every 9 seconds or so, and just found out that I have P115A-60 Low Fuel Level Forced Limit error code.

The defuel every 9 seconds only started after I unplugged/plugged in the fuel sender, wiped off the rear ABS plug, installed an exhaust system, installed a used metal CAC, installed some bushings on the FICM, and had the batteries disconned for over an hour while I upgraded the CAC, this past Saturday 8/29/2020.

The fuel gauge has been bouncing on/off E since I got the truck in July, but it's never caused a defuel situation.

I've googled the code and I've googled my E signal on my gauge cluster. I know that people will say that it's the fuel sender unit in the tank, or it's the gauge cluster, or check the fuses.

I don't believe it's the fuse because it's only cutting out when not on cruise control and there are no other cluster issues. (Except for speedometer being 12 off, but that's nothing new.)

I don't believe it's the fuel sender because I've tried to jump the sender at the tank by installing a jumper wire in the female plug at the tank, leading back to the cab and that changed nothing.

It could be the cluster - but would that cause P115A Forced Limit?

Is there a way to bypass the fuel sender unit to show it's full? Or not empty?

Is there a way to bypass the P115A-60 without replacing/repairing the cluster?

I can keep track of the tank with my mileage - at least until I'm able to get to the sender or to the cluster.
 

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If you leave the sender unplugged, it will show a full tank. It's a simple variable resistance device that the instrument cluster reads. 160 ohms (or greater - from an open circuit) will read full, and 15 ohms will read empty.

I doubt that your sending unit is the cause of your error. I don't find a P115A code (or anything similar) for a 6.0L in the service manual. What are you using to read the code?
 

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P115A (TSB-08-20-1) -
Defuel when the fuel level in the tank gets very low (well after the low fuel light comes on).
2005 and UP model years ONLY
 
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P115A (TSB-08-20-1) -
Defuel when the fuel level in the tank gets very low (well after the low fuel light comes on).
2005 and UP model years ONLY
Thanks Mark, My service manuals don't go up to 2005.
So by jumpering the fuel sending unit, it would definitely set that code and defuel.
I would check for shorted wiring between the sending unit and the instrument cluster. If the "hot" wire from the sender is shorting to ground, even intermittently, it would show an empty tank when shorted.
 

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The TSB wasn't issued until 2008, so it wasn't implemented until the 05's and up had a flash update after that 2008 date.
 

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Discussion Starter #6
So, my best bet would be to disconnect it at the back of the cluster?

I performed the gauge test and the fuel gauge worked. I also cut out the plug at the fuel tank for the sender and it still isn't registering.

If I cut the wires at the tank, clear the code, it should show full? Or if there is a short closer to the cluster it would still show empty, correct?
 

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Discussion Starter #7 (Edited)
Also, the jumper and the direct wire doesn't prove anything about the sender, does it? Could be a bad sender or dirty tank after all?

I do have 48 oz of clear diesel kleen in the 40 gal tank. Hopefully, if the tank is dirty, this'll clean it.
 

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So, my best bet would be to disconnect it at the back of the cluster?

I performed the gauge test and the fuel gauge worked. I also cut out the plug at the fuel tank for the sender and it still isn't registering.

If I cut the wires at the tank, clear the code, it should show full? Or if there is a short closer to the cluster it would still show empty, correct?
I would disconnect the connector at the instrument panel, and at the tank, then connect a multimeter set on ohms across the terminals on the tank connector. If it shows a closed circuit, then the wiring is shorted and needs to be fixed.
With the circuit disconnected at the instrument panel, it should show full. I wouldn't cut any wires till you determine there's a short.
You're correct that if there's a short between the cluster and instrument panel just disconnecting the tank connector, it would still show empty.
 

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Discussion Starter #9
I just remembered that I had tried driving with the sender unplugged and although there was no longer a defuel, there was also no oomph at all. I could only gradually accelerate...
 

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Discussion Starter #10
I removed the connection to the sender again, realizing that if there was a difference when it was unhooked, then it must be the sender. (Duh! Brain Fart)

And the reason I had no oomph is because my batteries were disconnected and because of the defueling, my trans had not relearned. After driving it through town and in the country for a mere 20 minutes, it started feeling more normal than when I got it!

It's a cab and chassis truck and has a slim fuel sender lock nut (?) so I'll dig into that later. For now I'm going to work on the parts I have. Thanks for your assistance and talking with me through my issue!
 

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Discussion Starter #11
My buddy has been telling me to purchase motorcraft parts to replace anything on this truck because they last longer. However, the fuel sender is $360 or something on RockAuto and the other brand is $260. Would it be bad to purchase the other brand?
 

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Discussion Starter #12
Haven't driven the truck since 9/9 because I found out on 8/30 that I have no rear brakes. Decided I didn't want to take any chances..

Looks like I'll just have to buy the motorcraft fuel sending unit for a cab and chassis - as it's different than others. But - $366, Ugh.
 

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Discussion Starter #13
Considering rebuilding the sending unit. However, despite searching, I don't see where anyone has found a good alternative for a rheostat - since that will probably be all that's required to change.

I really don't want to spend the $400 or so on a new aft fuel sender - but I guess I might just have to join everyone else. :-(
 

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You might be able to make that work, just replacing the sending unit itself on the pickup assembly. Not knowing what an 06 pickup assembly looks like, that's just a WAG.
It does say it fits an 06 F550 diesel, so it likely has the correct resistance values. Physically making it work might be a chore.
 

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Discussion Starter #16
You might be able to make that work, just replacing the sending unit itself on the pickup assembly. Not knowing what an 06 pickup assembly looks like, that's just a WAG.
It does say it fits an 06 F550 diesel, so it likely has the correct resistance values. Physically making it work might be a chore.
Yea - my F350 is a cab and chassis so the sender has to be "aft rear axle" which is the description of the F550 which is also a cab and chassis. According to RockAuto - an Aft Sender is the same for both an F550 and an F350, so I would imagine that the pickup assembly would be alright.
 

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Discussion Starter #17
I've contacted 2 separate parts places to see if their senders would work on my truck - 1 said it'd work for an F350 and the other said it'd work for a F550. I shared my VIN and was told no go.
 

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Discussion Starter #18
I'm going to purchase the PS77 from RockAuto for a 06 F550 because both the F550 and F350 show a PS200 for the fuel sending unit for an Aft Axle Fuel Cell.

I will also purchase the strainer - because it probably needs changed anyhow. Hopefully I'm saving $260, vs spending $460. I'll update this once I find out if it works or not. I just can't believe someone hasn't seen this as an opportunity to sell a cheaper fuel sending unit...
 
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