Check engine lights

[Gatorstan]

While coming home from a trip both of my check engine lights came on but no loss of power checked all fluids and all was fine no over heating and good oil pressure looking for any help

 

[Rich W.]

What are you driving?

 

[Gatorstan]

2014 Discovery Cummins 380

 

[Rich W.]

On a Freightliner chassis? Any codes?

 

[Gatorstan]

SPN 4364 Fpm 18

 

[Rich W.]

That's a somewhat obscure code for SCR insufficiency, I dont think its used anymore, but it means that for whatever reason, and there are many, your SRC is not doing its job well enough. Too much difference befween the before and after NOX sensors. So its probably DEF related, unless it's a bad sensor, but DEF related could be bad fluid itself, or a bad pump, or doser (injector), or even just a plugged up DEF filter. Have you ever had emissions problems with the coach before?

There are usually several codes when a problem like this occurs, helping to narrow it down. Do you have a good code reader or are you just using the dash display?

 

[Rich W.]

Also I dont recognize FPM. Could that be FMI 18?

 

[Rich W.]

I did a little quick research and it most likely is FMI 18. Anyway, this is fairly common, and its important to do the simple and cheap things first. Change the DEF, change the DEF filter if its been a while or if it has been sitting for months without being driven. Those are cheap, its an easy job, and its normal maintenance anyway.

Your book may show a 200-300k mile interval on it, but sometimes the coach don’t read the book. Actually that interval may work for trucks that drive every day, but the way we use our coaches is different and it should be changed annually.

So those are two quick easy things you can do before spending money and starting parts swapping. Then give it five or six ingition cycles to see if it clears. It wont clear right away without code re-set equipment.

Also don’t get roped into the forced regen theory. Regens happen in the DPF which is after the SCR so it can’t have any impact on NOX sensing upstream. Its important to keep up on the DPF and do your regens, but it wont slove this problem.

If you do nothing, you will eventually experience derating and it will probably be in a couple hundred miles or less. So its improtant to get on this and see what’s going on. FMI 18 means low severity, but that’s for now. It can, and probably will change, and not for the better. You might already be at 25% derate and just not notice it. You wouldn’t unless you were towing heavy and/or climbing long steep grades.

So thats it for now. More codes would be helpful and you may need a good code reader for that. Also the ability to re-set emissions codes is nice. I use OTR Diagnostics for that but there are other non-subscription options available.

 

[Gatorstan]

Thanks for the help and taking it to a friend who has a better code reader but I think that I will drain the def tank and other than trying siphonthe tank is there a drain plug and also where is the filter and is it hard to find and get to

 

[Rich W.]

Ive read that some Spartan chassis DEF tanks have a drain, but mine doesn’t and I think that most dont. I just siphoned mine out and the waste DEF is basically liquid fertilizer so you can dispose of it accordingly. Also change the filter. Its about $120 from Cummins, but the exact same filter in a Bosch box is less than $50.