203B Code, 2021 6.7L

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Mar 10, 2023 | 05:04 AM

TAD350

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3rd Gear

Joined: Jan 2021

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From: Michigan

203B Code, 2021 6.7L

My F350 Lariat, 6.7L w/40,000 miles is throwing a 203B code. I started thinking the gage was showing higher DEF levels than actual based on the miles driven and past usage rate. Now I have started to throw the 203B code. Is it likely the sensor? Reviewing the site, I see a number of issues in 2017,2018 but nothing more recent unless I am missing it. Have there been any recent problems that anyone is aware of?

Mar 10, 2023 | 07:25 AM

Ltngdrvr

Lead Driver

Joined: Nov 2005

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Possibly the sensor, but could also be a harness or harness connector issue.
https://www.engine-codes.com/p203b_ford.html

Mar 10, 2023 | 12:04 PM

morehouse7

Fleet Mechanic

Joined: Mar 2021

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This was one of the issues that can pop up with bad batteries

Mar 11, 2023 | 05:08 AM

TAD350

Thread Starter

3rd Gear

Joined: Jan 2021

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From: Michigan

Thanks for the feedback folks. The check engine went out yesterday, the day after I topped off the DEF. I will check the batteries and start looking at the connections.

Oct 6, 2023 | 08:46 AM

Drydenhayfarms

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Joined: Feb 2023

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My 22 6.7 had similar issues. Turned out some of my nox sensor connections had water in them. Dried them out and filled with dielectric grease. Been fine last 30k miles