S1
Fault Identification
Parse and classify the incoming fault code — SPN/FMI, OBD-II, or natural language description.
The Architecture
What Is a Deterministic FSM?
A Finite State Machine (FSM) is a computational model that exists in exactly one of a finite number of states at any given time. Transitions between states are triggered by specific inputs — in this case, fault codes, test results, and technician observations.
The word deterministic means that given the same inputs, the engine always produces the same output. There is no randomness, no hallucination, no creative interpretation. This is fundamentally different from large language models that generate probabilistic responses.
For diesel diagnostics — where a wrong answer costs real money and can cause safety failures — determinism is not optional. It's the foundation.
The 6 Diagnostic States
Every diagnosis progresses through these states in sequence.
S2
Symptom Correlation
Cross-reference reported symptoms against the knowledge base to build a probability-weighted fault hypothesis.
S3
Test Sequencing
Generate an ordered sequence of physical tests — cheapest and most likely first — to confirm or eliminate each hypothesis.
S4
Result Evaluation
Evaluate each test result against expected values. Narrow the fault tree based on pass/fail outcomes.
S5
Root Cause Determination
When sufficient evidence is gathered, lock in the root cause with a confidence score and supporting evidence chain.
S6
Repair Plan Generation
Output a prioritized repair plan with part numbers, torque specs, and verification steps.
4 Override States
Special-case handlers that activate when standard state progression is insufficient.
Intermittent Fault Submodule
Activates when a fault is present in history but not currently active. Adjusts test sequencing for intermittent conditions.
Multi-Code Cascade Handler
Detects when multiple related fault codes are present and resolves the root cause before addressing downstream codes.
Inconclusive Result Handler
When test results are ambiguous, the engine requests additional data or escalates to the Technician Chat™ module.
Emergency Override
For safety-critical faults (brake, steering, fire risk), the engine immediately surfaces the highest-priority action.