SPN 2791 FMI 0 — EGR Valve Control Above Normal / Over-Position
EGR above-normal position class is feedback and stuck-open diagnosis. Cooler replacement for a valve stuck open with high position feedback is the most documented misdiagnosis on this fault class.
Fault Overview
SPN 2791 FMI 0 indicates the EGR valve control or position is above the expected maximum — the over-position class. Carbon holding the valve open, position sensor bias high, actuator control faults, and calibration issues are the primary causes. Feedback circuit proof and command-response testing are required before any cooler or EGR package replacement.
Engine & Platform Coverage
Symptoms
- •EGR position above maximum on scan tool
- •Valve stuck open with high position feedback
- •Soot increase from excessive EGR flow
- •Rough idle with EGR stuck open
- •Cooler replaced without resolving the over-position fault
Possible Causes
- 1.Carbon holding the EGR valve open
- 2.Position sensor bias high producing false over-position reading
- 3.Actuator control faults preventing valve closure
- 4.Calibration issues after valve service
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
3 steps locked behind Technician Mode- 1Step 1 — Feedback Circuit Proof: Verify position feedback circuit integrity. A position sensor biased high will produce a false over-position reading without actual mechanical over-travel.
- 2Step 2 — Command Closed and Observe Actual: Command the EGR valve closed with a scan tool and observe actual position response. Actual position remaining high at commanded closed supports stuck open or biased feedback.
- 3Step 3 — Inspect Carbon Binding: Inspect the EGR valve for carbon binding holding it open. Carbon packing is a common cause of EGR valve stuck-open conditions on high-mileage engines.
- 4Step 4 — Service or Replace Valve as Evidenced: Clean or replace the EGR valve after carbon binding is confirmed. Replace the valve assembly after actuator failure is confirmed. Proceed to cooler or EGR package diagnosis only if the valve is proven to close correctly and flow is still excessive.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Clean EGR valve if carbon binding is confirmed and cleaning is approved.
- 2Replace EGR valve assembly after actuator failure is confirmed.
- 3Repair position feedback circuit if sensor bias is confirmed.
- 4Proceed to cooler diagnosis only after valve is proven to close correctly.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Start Diagnosing This Fault Now
AI Diesel Tech walks you through every evidence gate in the correct order. Choose the plan that fits your shop.
Related Resources
Related Fault Codes
AI Diesel Tech — The Technician's Diagnostic Engine
AI Diesel Tech diagnostic logic is built by an ASE Certified Diesel Technician and engineered for professional shop use. Trusted by technicians nationwide — used in shops, fleets, and training programs.
Summary
SPN 2791 FMI 0 is an EGR over-position fault. Prove feedback circuit integrity and valve closure response before any cooler or EGR package replacement.