If your Fendt tractor (or any SCR-equipped diesel machine) shows SPN 8342 FMI 2 with a message like “AdBlue (DEF) metering control under pressure”, it means the SCR system is not controlling AdBlue® pressure correctly.
Under real-world operating conditions, this fault is common. It is usually caused by contamination, crystallisation, or pressure feedback issues rather than random failure. Because of this, identifying the cause early can help prevent unnecessary downtime and SCR system damage.
What does SPN 8342 FMI 2 mean?
Simply put, this fault points to a problem in the AdBlue® dosing system, which injects AdBlue® into the exhaust to control emissions.
• SPN 8342 → AdBlue® metering / pressure control
• FMI 2 → Pressure signal is unstable or implausible
In practice, the issue usually comes down to one of the following:
• Incorrect pressure feedback (sensor, wiring, connector), or
• A restriction caused by crystallisation or blockage
Most common causes (real-world)
In everyday operation, common causes seen in the field include:
• Moisture or corrosion in electrical connectors
• Loose or damaged wiring
• White urea crystal build-up in injectors or lines
• Poor-quality or contaminated AdBlue®
• Incomplete purge cycles after shutdown
What to do when this fault appears?
✔ Do not ignore repeated warnings
Instead, note when the fault appears and whether it clears after restart.
✔ Check AdBlue® quality before topping up
If there’s any doubt about contamination or storage, stop and verify the source.
✔ Visually inspect only
Look for white crystals, leaks, kinked lines, or moisture in connectors.
✔ Allow proper shutdown
Before switching off, let the engine idle briefly so purge cycles can complete.
✔ Contact a workshop early
By providing the exact fault code and operating conditions, unnecessary part replacement can often be avoided.
⚠ Never add water, additives, or “fixes” to the AdBlue® tank.
How to prevent this fault
In most cases, SPN 8342 FMI 2 faults are preventable by:
• Using ISO 22241–compliant AdBlue®
• Storing AdBlue® in clean, sealed containers
• Avoiding diesel, water, or dirt contamination
• Following correct shutdown procedures
👉 Learn more about selective catalytic reduction (SCR) technology
👉 Learn what AdBlue® is and why quality matters
Final takeaway
As a result, SPN 8342 FMI 2 is rarely a random failure. Instead, it is a warning that AdBlue® quality, handling, or system cleanliness needs attention.
Using certified AdBlue® from trusted suppliers like Blue Sky AdBlue® helps protect SCR components and reduce costly downtime.
Blue Sky Tip
High-quality AdBlue® isn’t just about emissions compliance — it’s about protecting expensive SCR components and keeping equipment running reliably.
