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Check engine light at start up.

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So. I  recently started getting a check engine light at start up of my M/H. 2004 Holiday Rambler Neptune 36PDQ with a Cummins 5.9 300 hp isb. Tried to find the codes but not sure I understand them. Can anyone decode them? After about 10 minutes the CEL turns off.

Thanks Rich 




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Ive had same issues decrypting the scangage codes with no luck. Last time I called them they sent me to bigdieselcodes.com but that didn’t help either. 

on my coach i have 2 switches under /inside the dash  by steering column labled diag and idle, heres my notes on how to use them to display the codes by flashing the CEL light, these will be cummins codes easily found online. Hope this helps 

To check DTC: Diag sw show’s first code then idle up sw show next etc


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SPN 111 is coolant level and the FMI #1 is the mode which is critical.  
Cannot find the other two as hard faults?

In essence this code is saying that the data is valid and coolant level is low to the point of critical( at least from a sensor point of view).  Should be a RED indicator lamp illuminated?

SPN# means “Suspect Parameter Number”

FMI# means “Fault Mode Identifier”

Hope this helps

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  • 3 weeks later...

Do you have a Cummins Quickserve account, if so there is a Fault Code Lookup.   https://quickserve.cummins.com

You have to create an account and then once you have the account you can register your engine by SN.  The codes are specific to each model engine. 

The fault code search is under the service tab.  If it does recognize the code it will show you the cause but will also provide links on how to troubleshoot, multiple layers of information. 

There is also a parts tab which will provide info there.   But it takes some time to learn to use the website, but time well spent.


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