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Intro and Code Troubles!

Jan 16, 2022
58
10
Truck Year
2017
Hey y'all. I just got my new to me 2017 Ram 1500 Big Horn EcoDiesel, with 60,000 miles, about 3 or 4 weeks ago (after my '16 1500 Pentastar got t-boned and totaled).
So far, I dig the new gal, but the diesel intimidates me a little. I've never had one, but I'm willing to learn.

Yesterday (~30° F), after driving for about a mile, I got a ding and the CEL. I went home and read the code: P0198 (oil temp high). I drove it around for a few, and all seemed fine, and the oil temp was ok, so we ran our errands (oil never got above 205). The truck sat for about an hour and a half. When I got back in, it started fine and the CEL was gone, but there was a brief 'service shifter' message. On the way home, I monitored the temperature and it stayed pretty low. All of a sudden, I got a ding and the CEL. The temp shot up well over 300 degrees, then back down to normal, then up and back down. Then it was stable.
My thoughts are a bad oil temperature sensor.

That evening, after the truck sat for a few hours, I decided to check it out again. I fired it up, I had the CEL, got the 'service shifter', and a 'check electronic braking system' message, and the traction control light. Geez.
I scanned it again and got the P0198 and a U0121 (something about ABS, I think).
My thoughts are now leaning towards this being an electrical gremlin, wiring harness issue, or something that is challenging to diagnose.
This morning (27 degrees), I fired it up. No messages, no Traction Control light, but did have the CEL.

Other than the barrage of lights, the truck seems fine. I did find a shop that'll see diesels (harder than I thought) and they're going to run a thorough diagnostic today (hopefully).

Have any of you fine folks encountered such a thing? My '16 ran flawlessly for the 40ish thousand miles I put on it. This one was running great... I'm perplexed.
If anyone has some advice or experience with these symptoms, I'd love to know the solution.
 

Tremper126

Moderator
Staff member
Feb 15, 2019
908
331
Truck Year
2014
Check the main connection plug under your drivers side floor board under the truck by the frame. Sounds like the random code here and there is a ground / communication issue
 
Jan 16, 2022
58
10
Truck Year
2017
Thanks, Tremper126, I'll look into that if it flares up again.

The shop checked it out and only got the one code for the oil temperature sensor. They ran it and checked it... Ran it and checked it... They couldn't get it to do anything.

Does anyone here have experience with changing the oil temperature sensor? I haven't really checked into it, but the shop was going to charge about $350. I'm thinking I can probably do it for less.

I'll update this post with any more developments.
 

John Jensen

Well-Known Member
Mar 22, 2016
840
416
Truck Year
2016
Just a thought. I have read where members had similar electrical reactions, and it turned out their battery was failing.
 
Jan 16, 2022
58
10
Truck Year
2017
Just a thought. I have read where members had similar electrical reactions, and it turned out their battery was failing.
Thanks for the tip. I'd seem some situations like that, too. But my battery seems to be doing fine. Running between 13 and 14 volts. I'll keep an eye on it.
 
Jan 16, 2022
58
10
Truck Year
2017
Since I brought it home from the shop a few days ago, no codes and everything has be fine... Until a few minutes ago.
I was driving (27 degrees) to the store, and my CEL illuminated.
Truck seems fine. I read the code, expecting the same as last time, but the P0198 code was gone, replaced with U0402 and U0121.

What gives?!?!
 
Jan 16, 2022
58
10
Truck Year
2017
Ok. I cleared the code. Once it warms a little, I'm gonna check the plug out. The battery and connection seems good. Do I check it from the cab, or underneath?

How common is this issue?
 

Tremper126

Moderator
Staff member
Feb 15, 2019
908
331
Truck Year
2014
Underneath attached to the inside of the frame. Salty areas from beaches or snow removal make it more frequent
 
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