Ford diesel DEF codes: connector moisture and fretting. See the manufacturer document, vehicle conditions, exclusions and questions for a qualified shop before assuming a repair.
This is a research summary of a manufacturer communication, not a diagnosis for your car, a DIY repair procedure or confirmation of warranty or recall eligibility. No qualified technician has approved a repair for your individual vehicle here.
This historical communication is conditional. The current revision, VIN/build eligibility, measured diagnosis and any warranty or recall decision are not established here. Ask the manufacturer or a qualified shop to check the complete current document.
Read the Ford original: Diesel DEF harness moisture/fretting and multiple DTCs · Check open recalls by VIN at NHTSA Source date: 2023-05-22; research checked: 2026-11-01.
What prompted this manufacturer document
- Moisture or fretting at specified DEF-system connectors can contribute to the listed faults.
Which vehicle conditions must be checked
Each row below retains its own conditions. Do not combine engines, years or models across rows to create new applications. A listed model is not proof that a particular VIN is affected.
- Ford F-150 · 2018, 2019, 2020, 2021 · 3.0L diesel
- Ford Super Duty · 2017, 2018, 2019, 2020, 2021, 2022 · 6.7L diesel; Built on or before 2022-03-08
- Ford F-650 / F-750 · 2016, 2017, 2018, 2019, 2020, 2021, 2022 · 6.7L diesel
- Use the correct engine/model/build-date combination.
- The relevant C3613/C4851/C3610 connector path depends on the vehicle.
Codes recorded in this document
A root listed only as an appearance has no separately verified meaning here. Preserve every suffix and module name; a shared root does not transfer a repair branch to another vehicle.
| Root | Raw form | Meaning in this source, if established |
|---|---|---|
| P21DD | P21DD | Appears in the document; individual meaning not verified |
| P20BA | P20BA | Appears in the document; individual meaning not verified |
| P20B9 | P20B9 | Appears in the document; individual meaning not verified |
| P204C | P204C | Appears in the document; individual meaning not verified |
| P208A | P208A | Appears in the document; individual meaning not verified |
| P208B | P208B | Appears in the document; individual meaning not verified |
| P208C | P208C | Appears in the document; individual meaning not verified |
| P203B | P203B | Appears in the document; individual meaning not verified |
| P205B | P205B | Appears in the document; individual meaning not verified |
| P21CD | P21CD | Appears in the document; individual meaning not verified |
| U02A2 | U02A2 | Appears in the document; individual meaning not verified |
What an owner can record safely
- Record DEF warnings, countdowns, temperature and recent water/wiring events.
What the source does not prove
- Do not assume a refill fixes an electrical fault, or disable an emissions device to hide it.
- A code or message alone does not establish a failed part, a safe-to-drive decision or an approved repair for this VIN.
- A service bulletin is not automatically a recall or free warranty repair. Confirm current eligibility directly.
Questions for the repair shop
- Were the correct connectors inspected before a pump/heater/tank was recommended?
- Does a later revision or a current recall change the source's original advice?
- What measurement or inspection confirms the cause, and how will the repair be verified?
Read the original record
The linked communication may be revised after the research date. Compare its document number, exact vehicle table, diagnostic preconditions and exclusions with a qualified technician. This page paraphrases selected facts and does not reproduce the manufacturer procedure.
Sources and scope
- Ford — Diesel DEF harness moisture/fretting and multiple DTCs (23-2161) Document: 2023-05-22 · Research checked: 2026-11-01
Research snapshot: 2026-11-01. Source documents may have newer revisions. Verify current instructions and VIN eligibility with the manufacturer.