Reductant Quality Issue
The diesel exhaust fluid (DEF) quality is not within acceptable limits.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer is detecting that the quality of the diesel exhaust fluid (DEF) isn't good enough, which can affect emissions and performance.
What the computer is actually seeing
The onboard computer monitors the DEF quality using signals from the DEF quality sensor which should produce a voltage signal between 0.5 to 0.8 volts for acceptable quality. A lower or higher value means the DEF is potentially contaminated or diluted.
What a healthy reading looks like
DEF quality sensor should read 0.5 to 0.8 volts for good quality; readings below 0.2 volts or above 0.9 volts indicate quality issues.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Verify DEF fluid level; it should be above the minimum mark (usually around 2 inches from the bottom).
- 22. Check the DEF fluid for contamination or dilution (should be clear, not cloudy).
- 33. Inspect the wiring and connectors for the DEF quality sensor for damage or corrosion.
- 44. Use a scan tool to read the DEF quality sensor voltage; expected value is between 0.5 to 0.8 volts. If outside this range, proceed to next step.
- 55. If voltage is out of range, replace the DEF quality sensor and clear codes; monitor for recurrence.
Common causes
- Contaminated DEF fluid
- Diluted DEF fluid
- Faulty DEF quality sensor
- Wiring issues to the DEF sensor
- Exhaust system leaks affecting sensor readings
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable, but you may notice reduced power and increased emissions; fix it soon.
Will this code come back after clearing it?
If the DEF fluid quality is not corrected or the sensor is faulty, it will likely return.
Why does this code sometimes pair with P20C1?
P20C1 indicates a specific fault with the DEF quality sensor, often indicating it's not just the fluid quality but also sensor performance.
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