Not a tech, nor do I play one on TV, but I have a question

As a driver.....

Last week, I was driving and my "check engine" light came on. I thought, 'oh crap, what now?'..

At my next stop, while getting fuel, I popped the hood to look for any obvious reasons. Besides needing a little coolant and WW fluid, which I added, I found none. I turned off the master power while doing this, and nothing worked.

Fast forward 4(?) days and a couple thousand miles, the light went out. No codes, no change in performance.......

I am wondering what the cause could have been?

 

Too many possibilities. Hooking up will give an idea. I would keep running it and pay attention to operating conditions when the light occurs. Its one thing of many I have learned that trucks dont fix themselves. Its still broken, just not right now.

That being said, sometimes it is easier to wait until the light is on or the fault is active to dive into troubleshooting.

Appears as though your issue has fixed itself.......for now.

 

Paccar will do that if it sees a drop in fuel pressure. Like filter is getting plugged or the o-ring on the secondary filter got damaged upon install.

 

2019 freightliner?

 

Was it really cold then? Last PM done?

 

No, and less than 5000 miles(1/20 @ 361,000; now 366,000)

 

I don't claim to be any kind of mechanic either lol. I guess if it ain't broke...probably charge you at Freightliner to hook up the computer and check it out

 

I have a Mack and sometimes when it's cold out (which you said it wasn't) I will get the SCR BS because it doesn't get hot enough on the road for a regen.

 

I could be as simple as too much water in the fuel..

 

Could be similar to modern cars. They will sometimes throw an engine light while running self check tests.