Engine Exhaust 1 NOx 1 — Data Drifted High
The VOLVO-MACK-SPN3216-FMI20 (Volvo/Mack D/MP Series) diesel fault code means: Engine Exhaust 1 NOx 1 — Data Drifted High. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
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What Are the Symptoms of VOLVO-MACK-SPN3216-FMI20?
- Check Engine or an aftertreatment warning light
- A Engine Exhaust 1 NOx 1 reading that jumps or disagrees with related sensors
What Causes VOLVO-MACK-SPN3216-FMI20? (Most Likely First)
- Failing sensor High
- Loose, corroded or chafed connector or wiring High
- Sensor contaminated or installed wrong Medium
Can I Still Drive with VOLVO-MACK-SPN3216-FMI20?
Short distances only. VOLVO-MACK-SPN3216-FMI20 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does SPN 3216 FMI 20 mean?
SPN 3216 is "Engine Exhaust 1 NOx 1" in the SAE J1939 Digital Annex, and FMI 20 means the reading has drifted high over time, which usually points to sensor aging. Together they say the reading has drifted high over time, which usually points to sensor aging for that parameter.
Is this a Volvo / Mack-specific code?
No. It is a standard J1939 SPN and FMI pair, so the parameter and failure mode mean the same on any J1939 engine. What Volvo / Mack checks before setting it, and what the truck does about it, is in Volvo / Mack service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose VOLVO-MACK-SPN3216-FMI20?
Watch the live Engine Exhaust 1 NOx 1 value for dropouts while wiggling the harness.
Inspect the connector and wiring to the sensor.
Compare the reading with related sensors under the same conditions.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SPN 3216 record in the ISOBUS Data Dictionary (ISO 11783 online database), reproducing the SAE heavy-duty Digital Annex (DA) name "Engine Exhaust 1 NOx 1". Establishes what the SPN names, not what a Volvo / Mack display shows for it.ISO 11783 online database copy of the SAE J1939 Digital Annex SPN list — readable, not SAE’s current edition
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
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