What are the most likely causes of SPN 5246 FMI 0?

Earlier DEF quality or level code left uncorrected; Diluted or contaminated DEF in the tank; Failing DEF quality sensor

How do you diagnose code SPN 5246 FMI 0?

1) Measure DEF concentration with a refractometer — 32.5% urea 2) Read active and inactive SCR codes and their order — The root code preceding 5246 is identified 3) Inspect the DEF doser and nozzle — Clean nozzle, even spray pattern

What part is usually replaced for SPN 5246 FMI 0 and how much does it cost?

Forced regeneration (shop): $150–$500 USD (aftermarket to dealer), plus 1–2 h of labor.

← All codes

SPN 5246 FMI 0

STOP

DEF inducement

The DEF system triggered the derate: road speed is about to be limited.

SPN 5246 FMI 0: The DEF system triggered the derate: road speed is about to be limited. Stop: this is a stop-now code. Park safely and do not keep driving until it is checked.

Electrical · SCR / DEF

Can I keep driving?

Stop: this is a stop-now code. Park safely and do not keep driving until it is checked.

What it means

SCR inducement reached its final level: the ECM applies a torque derate and then limits road speed to 5 mph. It almost always follows a DEF quality, level or dosing code that was not corrected in time.

Most likely causes

Earlier DEF quality or level code left uncorrected
Very likely
Diluted or contaminated DEF in the tank
Very likely
Failing DEF quality sensor
Likely
DEF doser plugged with crystals
Likely

Tests, cheapest and most decisive first

1. Measure DEF concentration with a refractometer
Expected result: 32.5% urea
Tool: Refractometer
2. Read active and inactive SCR codes and their order
Expected result: The root code preceding 5246 is identified
Tool: J1939 scanner
3. Inspect the DEF doser and nozzle
Expected result: Clean nozzle, even spray pattern