Frustated in Havasu

[Rich W.]

this is from page two of the attachment that the schematic in post 17 came from (I should have read it more carefully at the time):

“Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
• Diesel exhaust fluid injection into the aftertreatment system is disabled.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.”

So this further explains your first two codes and increases the likelyhood that it is just this relay. The DEF head and dosing unit et al cant function under this condition.

I looked at half a dozen code lists before I found fault codes 4155 and 4156 associated with 5746. Most of my charts list SPNs but not the associated fault codes. My Cummins lists go by fault code but you have to dig to find the SPN because they are not in numerical order on the charts, and the dash diagnostics don't provide fault codes.

This is another reason they shouldn’t just grab an SPN and make a guess that can cause a customer to be stranded for months for a part that he might not need. I never wanted to make diesel emissions a hobby but my personal experiences (and experiences like yours) necessitated it. My goal is to never be stranded by my emissions system. Its also why Im interested in your case because every new situation adds to my tool box.

These are links for the faults codes for SPN 5746. Diagnostics should show one of them. I use OTR Diagnostics and it gives me all the codes, plus pages like these, so I am well armed when a dash light comes on:

https://f01.justanswer.com/NicholasM1019/323b14d6-8344-4179-9219-611d078b1b17_189-fc4155.pdf

https://f01.justanswer.com/diesel3153/57166ad8-1d62-4c11-8688-d506285291a8_isx_4156_fault_code.pdf

 

[Flashflood]

Your correct! Thank you for all your help. We’re seeing a new mechanic next week.

 

[Engleman]

2016 fleetwood pace arrow 38k 340hp isb. Was headed home and stopped to top off the diesel and def as we usually do because we live in the foothills. We were a couple of hours from home and about 1/2 way there i had a def light come on the display bar. I pulled over and scrolled to find the code. Looked up online to find that the code meant low def. After just topping off the tank. I got ahold of cummins and gave them the code and they told me not to worry about it. They said to keep on driving on home and that the warning light would go out, it did, and that the code would clear itself, and the code did clear. That was probably 4 years ago with no issues since!

 

[Flashflood]

Your correct! Thank you for all your help. We’re seeing a new mechanic next week.

2016 fleetwood pace arrow 38k 340hp isb. Was headed home and stopped to top off the diesel and def as we usually do because we live in the foothills. We were a couple of hours from home and about 1/2 way there i had a def light come on the display bar. I pulled over and scrolled to find the code. Looked up online to find that the code meant low def. After just topping off the tank. I got ahold of cummins and gave them the code and they told me not to worry about it. They said to keep on driving on home and that the warning light would go out, it did, and that the code would clear itself, and the code did clear. That was probably 4 years ago with no issues since!

Wow crazy

 

[Rich W.]

I logged on to Cummins QuickServe and ran SPN 5746 for both possible fault codes. This isnt new, different, or conflicting information, but it is from the horses mouth and these links should be helpful when talking to a service writer/manager. Hope this helps:

Cummins QuickServe links SPN 5746, fault codes 4155 and 4156

https://quickserve.cummins.com/qs3/pubsys2/xml/en/procedures/193/193-fc4156.html

https://quickserve.cummins.com/qs3/pubsys2/xml/en/procedures/193/193-fc4155.html

 

[Flashflood]

I logged on to Cummins QuickServe and ran SPN 5746 for both possible fault codes. This isnt new, different, or conflicting information, but it is from the horses mouth and these links should be helpful when talking to a service writer/manager. Hope this helps:

Cummins QuickServe links SPN 5746, fault codes 4155 and 4156

https://quickserve.cummins.com/qs3/pubsys2/xml/en/procedures/193/193-fc4156.html

https://quickserve.cummins.com/qs3/pubsys2/xml/en/procedures/193/193-fc4155.html

Thank you

 

[Flashflood]

Thank you

 

[Flashflood]

These are my current fault codes on our tiffin, apparently not the def thank you Rich for your amazing help! Anyone else ever had these or know how to fix them?

 

[Rich W.]

So 3582 is the only active code. As it states, SCR efficiency is sub-par. That means it’s not getting sufficient DEF, which again points to either the pump or filter or both, with a less likely possibility that the doser is malfunctioning.

Unfortunately there is no sensor for the pump output (pump pressure), so when the pump goes bad it becomes a guessing game with the only clue being the resultant insufficient SCR effectiveness.

The good news is the test is uncharacteristically simple - a pressure gauge on the DEF output line - should be between 110 and 150 psi IIRC.

 

[Flashflood]

So 3582 is the only active code. As it states, SCR efficiency is sub-par. That means itw not getting sufficient DEF, which again poimts to either the pump or filter or both, with a less likely possibility that the doser is malfunctioning. Unfortunately there is no sensor for the pump output, so when the pump goes bad it becomes a guessing game with the only clue being the resultant insufficient SCR effectiveness.

The good news is the test is uncharacteristically simple - either a pressure gauge on the DEF output line - should be between 110 and 150 psi IIRC.

I owe you a Starbucks