Engine Exhaust Gas Recirculation 1 Differential Pressure — Data Erratic, Intermittent or Incorrect
The DD-411-2 (Detroit Diesel DD Series) diesel fault code means: Engine Exhaust Gas Recirculation 1 Differential Pressure — Data Erratic, Intermittent or Incorrect. This is a moderate severity code.
This is a standard J1939 fault, not a proprietary code. DD-411-2 is how this equipment displays SPN 411 with FMI 2 (data erratic, intermittent, or incorrect) under the SAE J1939 standard used across heavy equipment. The same SPN can appear on any J1939-compliant machine regardless of brand — so cross-referencing it against your engine maker's documentation is valid even when the equipment brand differs.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
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What Are the Symptoms of DD-411-2?
- Check Engine or an aftertreatment warning light
- A Engine Exhaust Gas Recirculation 1 Differential Pressure reading that jumps or disagrees with related sensors
What Causes DD-411-2? (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 DD-411-2?
Yes, but fix soon. DD-411-2 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.
Frequently Asked Questions
What does SPN 411 FMI 2 mean?
SPN 411 is "Engine Exhaust Gas Recirculation 1 Differential Pressure" in the SAE J1939 Digital Annex, and FMI 2 means the reading is implausible, jumping, or disagrees with other sensors. Together they say the reading is implausible, jumping, or disagrees with other sensors for that parameter.
Is this a Detroit Diesel-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 Detroit Diesel checks before setting it, and what the truck does about it, is in Detroit Diesel service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DD-411-2?
Watch the live Engine Exhaust Gas Recirculation 1 Differential Pressure 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 411 record in the ISOBUS Data Dictionary (ISO 11783 online database), reproducing the SAE heavy-duty Digital Annex (DA) name "Engine Exhaust Gas Recirculation 1 Differential Pressure". Establishes what the SPN names, not what a Detroit Diesel 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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