SPN 3464 FMI 31 — Engine Throttle Actuator Control Condition Exists
Throttle actuator conditions are often carbon plus control integrity. Carbon buildup after short-trip service cycles and connector unplugged after intake work are the most documented patterns. The FSM enforces carbon versus electrical split before assembly replacement.
Fault Overview
SPN 3464 FMI 31 indicates an intake throttle actuator condition exists. The OEM defines the exact trigger — position error, control fault, or inhibit class. Carboned plate, failed actuator, position feedback fault, wiring issues, and software adapts lost after service are the primary causes. Carbon buildup after short-trip service cycles and connector unplugged after intake work are documented patterns. Replacing the throttle body assembly before cleaning and verifying control is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •Intake throttle actuator fault
- •Regen throttle not moving
- •Throttle plate stuck
- •EGR throttle control code
- •Regen temp insufficient from throttle fault
Possible Causes
- 1.Carboned plate — carbon buildup on throttle plate producing binding and position error
- 2.Failed actuator — failed actuator producing no movement or erratic response
- 3.Position feedback fault — position feedback fault producing position error
- 4.Wiring issues — wiring issues producing control fault
- 5.Software adapts lost after service — software adapts lost after service producing position error
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 — Command Sweep: Command a sweep of the intake throttle through its full range. Binding shows lag; electrical faults show dropout or no movement with good power. Carbon buildup after short-trip service cycles is a documented cause — inspect for carbon if binding is confirmed.
- 2Step 2 — Inspect Carbon: Inspect the throttle body for carbon buildup. Carbon buildup after short-trip service cycles is a documented pattern. Inspect the throttle plate and bore for carbon deposits. Clean the throttle body if carbon binding is confirmed and cleaning is approved per OEM procedure.
- 3Step 3 — Circuit Checks: Perform circuit checks. Connector unplugged after intake work is a documented pattern — always inspect the throttle body connector after any recent intake service. Verify throttle body connector integrity, reference voltage, ground, and signal circuit.
- 4Step 4 — Clean vs Replace Decision Based on Wear and Response: Make the clean vs replace decision based on wear and response. Clean the throttle body if carbon binding is confirmed and cleaning is approved. Replace the throttle assembly if actuator or sensor failure is confirmed after cleaning and circuit proof ($300–$1,200).
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
1 steps locked- 1Clean throttle body if carbon binding is confirmed and cleaning is approved per OEM procedure.
- 2Repair connector or harness if circuit fault is confirmed.
- 3Replace throttle assembly if actuator or sensor failure is confirmed ($300–$1,200).
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
Throttle actuator conditions are often carbon plus control integrity. The AI Diesel Tech FSM enforces carbon versus electrical split before assembly replacement.