SPN 2791 FMI 3 — EGR Valve Control Circuit Voltage Above Normal
EGR control high-voltage codes are open-circuit electrical diagnostics first. An EGR assembly replaced for a connector left unplugged after cooler service is the most documented misdiagnosis — the control circuit was never open because the valve failed; it was open because the connector was never re-seated.
Fault Overview
SPN 2791 FMI 3 indicates the EGR valve or actuator control circuit voltage is above the normal maximum — an open circuit or high-signal class fault. Open control wire, unplugged connector, failed actuator with internal circuit open, blown supply fuse, and damaged harness after cooler service are the primary causes. EGR assembly replaced for an open connector left unplugged after cooler R&R is the most documented misdiagnosis.
Engine & Platform Coverage
Possible Causes
- 1.Unplugged EGR actuator connector after cooler or valve service
- 2.Open control wire from heat damage near EGR plumbing
- 3.Failed actuator with internal circuit open
- 4.Blown supply fuse for the EGR actuator circuit
- 5.Damaged harness after EGR cooler removal and reinstallation
Wiring & Circuit Notes
Inspect the actuator connector at the EGR valve for heat damage and pin tension after repeated service. Check for brittle insulation near EGR plumbing. Verify the connector is fully locked — EGR service frequently disturbs the actuator connector and a partially seated connector is a common cause of this code.
DVOM Specs & Sensor Tests
Confirm control and supply voltage at the actuator connector during a commanded position change. Measure actuator resistance versus OEM specification. Continuity from the driver module to the actuator must be intact. Mechanical binding inspection is only appropriate after the control circuit is proven electrically sound.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Visual inspection of actuator connector — confirm fully locked after any recent EGR service
- 2Confirm supply and control voltage at actuator connector during command
- 3Measure actuator resistance versus OEM specification
- 4Check continuity from ECM/driver module to actuator
- 5Command EGR movement after circuit is proven intact
- 6Mechanical binding inspection only if electrically good and actuator fails to respond
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
4 steps locked- 1Visual inspection of actuator connector — confirm fully locked after any recent EGR service
- 2Confirm supply and control voltage at actuator connector during command
- 3Measure actuator resistance versus OEM specification
- 4Check continuity from ECM/driver module to actuator
- 5Command EGR movement after circuit is proven intact
- 6Mechanical binding inspection only if electrically good and actuator fails to respond
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.
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Summary
SPN 2791 FMI 3 is an open-circuit electrical diagnosis. Connector inspection after recent service is the first gate — EGR assembly replacement is the last step, not the first.