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PACCAR SPN 411 FMI 16: Meaning, Causes & Fix

Exhaust Gas Recirculation (EGR) Differential Pressure — data implausible between sensor readings

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Diagnostic Reference

Field Details
Code SPN 411 FMI 16
Protocol J1939 SPN: 411 FMI: 16
Component EGR Differential Pressure Sensor / EGR System
Manufacturer PACCAR
Engine Series MX-13
Severity 🟠 CHECK SOON
SAE Reference SAE J1939-73 Digital Annex — SPN 411, FMI 16

Possible Causes

  1. EGR delta-P sensor tubes clogged asymmetrically (one tube blocked)
  2. Sensor diaphragm damaged from overpressure
  3. EGR cooler partially plugged causing uneven pressure
  4. EGR valve position sensor disagreeing with delta-P reading
  5. Water condensation in sensor tubes freezing in winter

Diagnostic & Repair Procedure

  1. Step 1: Remove both EGR delta-P sensor tubes and clean with carb cleaner and pipe cleaner
  2. Step 2: Verify both tubes are equally clear by blowing through them
  3. Step 3: Pressure test EGR cooler for partial blockage
  4. Step 4: Replace delta-P sensor if tube cleaning doesn't resolve
  5. Step 5: In cold climates, check for ice in sensor lines

Frequently Asked Questions

Is this a false alarm or a real problem?

CHECK SOON codes are rarely false alarms. The ECM has detected a parameter outside normal operating range. Sensor malfunctions can sometimes trigger false readings, but the majority of CHECK SOON codes indicate a developing issue that will worsen if left unaddressed. Use a diagnostic scan tool to verify sensor readings before replacing expensive parts.

Can I diagnose this without a scan tool?

Basic visual inspection can be performed without a scan tool — check wiring harnesses for chafing, connectors for corrosion, and related components for physical damage. However, to verify the fault, view live sensor data, and confirm the repair, a heavy-duty diagnostic scan tool (or a compatible OBD-II adapter with J1939/J1708 support) is strongly recommended for accurate diagnosis.

How soon should I schedule service?

Schedule service within the next 1–3 operating days. While the vehicle can continue operating normally, delaying repair increases the risk of the fault escalating to CHECK NEXT STOP severity. Additionally, some CHECK SOON conditions are precursors to emissions system faults that will trigger a mandatory derate if not addressed in a timely manner.

Diesel Repair Cost & Downtime Estimator

Enter estimated labor hours to calculate repair cost and potential fleet downtime losses. Based on national average diesel shop rate of $150/hr and daily revenue loss of $800/day for a parked truck.

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SPN 91 FMI 16 🟡 CHECK AT NEXT STOP
Accelerator Pedal Position
MID 130 PID 52 FMI 5 🟡 CHECK AT NEXT STOP
Transmission Oil Temperature Sensor
MID 128 PID 105 FMI 10 🟠 CHECK SOON
Intake Manifold Temperature

Associated Symptoms

Check Engine Light Egr Flow Insufficient Rough Idle At Cold Start Turbo Lag Fuel Consumption Increased Black Smoke Under Acceleration

References & Further Reading

Data Provenance: This fault code definition is derived from SAE J1939 standards. SPN 411 FMI 16 is defined in SAE J1939-73 Digital Annex. Diagnostic procedures sourced from PACCAR OEM technical service documentation. Not for safety-critical decisions. Consult a certified diesel mechanic before performing any repair. See our full disclaimer.