SYMPTOM → SYSTEM → EXACT YEAR

Diagnostic Center

Start with what the car is doing, then stay with the correct engine, model year and system. A symptom or code starts the test—it does not prove a part.

LT1 and LS1 procedures remain separate. Modified cars get their own paths when changed hardware or calibration can invalidate a factory assumption.

Resume Saved Diagnosis →

A mechanic’s approach

I use these paths the same way I would approach a car in the shop: preserve the complaint, test the system in the state where it fails, prove the fault, then choose the part. A code or symptom is a starting point—not a parts order.

Start here

Fastest route

Symptom RouterChoose the complaint first when you do not yet know the failed system.Start by symptom → Year & Engine NavigatorChoose the exact year and engine before using year-specific procedures or hard specifications.Choose application → Exact Test LibraryOpen the meter, pressure, electrical or mechanical test called for by a diagnostic path.Open tests → All Diagnostic JourneysComplete index when you already know the system or exact complaint.Browse index →

Engine & powertrain

Keep LT1 / LS1 separate

1993–1997 LT1Optispark/distributor, fuel, starting, charging, cooling, misfire and drivability paths by published year.Open LT1 → 1998–2002 LS1Starting, security, fuel, ignition, cooling, emissions and drivability with exact-year guardrails.Open LS1 → Transmission / Clutch / Rear Axle4L60E, T56, clutch-release, driveline and rear-axle diagnosis and compatibility.Open drivetrain → DTC Before PartsUnderstand what a code actually proves before replacing the component named in the description.Open DTC guide →

Electrical, body & HVAC

25+ year-old car systems

Battery Drain / ElectricalParasitic draw, charging and electrical starting points.Open electrical → Lighting / Headlamp DoorsHeadlamp doors, exterior lighting and related electrical complaints.Open lighting → Body / ConvenienceWindows, locks, keyless entry, gauges, wipers, washers, horn and other body systems.Open body path → HVAC / A/CBlower and compressor-clutch starting points with system-specific test logic.Open HVAC →

Brakes, steering & chassis

Noise, feel, ABS and modified hardware

Brake Feel / PulsationSeparate rotor, hub, hydraulic and installation causes before buying parts.Open brake path → ABS / Wheel SpeedWheel-speed and false-activation paths without automatically condemning a hub.Open ABS → Suspension / SteeringNoise, pull, wander and memory-steer starting points.Open chassis → Hub / Road-Speed NoiseSeparate tire, brake, hub and driveline noise before replacing a bearing assembly.Open noise path →

MODIFIED-CAR / AFTERMARKET EVIDENCE

Modified car diagnostics

Changed hardware, wiring, calibration, gearing, fuel systems, brakes and drivetrain parts can invalidate factory assumptions. These guides use verified factory information where applicable plus manufacturer documentation and modification-aware diagnostic reasoning. They are intentionally labeled separately from exact-year factory procedures.

Proof before replacement

FPV rule

SYMPTOM → TEST → ISOLATE → PROVE → PARTS VERDICT → REPAIR → VERIFY. When an exact-year value or procedure is not verified, FPV does not substitute a neighboring-year number just to fill the space.