STARTING SYSTEM
Car won’t crank
The engine does not rotate when starting. Separate battery, cable, starter-control, interlock, security, and starter faults before replacing anything.
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The engine does not rotate when starting. Separate battery, cable, starter-control, interlock, security, and starter faults before replacing anything.
Treat overheating as a stop-and-assess condition, then separate coolant loss, airflow, circulation, control, and combustion concerns.
Determine whether the battery is undercharged, unable to store energy, losing energy while parked, or disconnected by a cable fault.
Use when and where the vibration is felt to separate brake torque variation from wheel, hub, tire, steering, and suspension causes.
Use scan data and operating patterns to separate ignition, mixture, air, fuel, mechanical, mount, and control concerns.
Separate airflow, control, compressor-command, heat-rejection, refrigerant-circuit, and electrical concerns without venting refrigerant or guessing a charge.
Separate actual low tire pressure from a TPMS malfunction, sensor, compatibility, registration, or relearn concern.
Use the first starting split—cranks or does not crank—to choose the correct electrical, authorization, fuel, ignition, or mechanical diagnostic path.
Use operating conditions, code context, cylinder patterns, and targeted tests to separate ignition, fuel, air, mechanical, and control causes.
Classify an unfamiliar vehicle noise by location, timing, speed, load, and safety evidence before choosing a system-specific inspection path.
Classify an engine noise by when it occurs, where it is heard, and what warnings or operating changes accompany it before choosing a safe inspection path.
Separate battery state, mechanical drive, cable loss, alternator output, sensing, control strategy, and vehicle-load concerns before replacing the alternator.
Use the timing, affected circuits, electrical load, and vehicle state to separate a charging, connection, control, or individual lighting fault.
Separate a failed lamp or local connection from fuse, ground, wiring, control, and configuration concerns before replacing parts.
Separate a missing lamp or changed circuit load from socket, wiring, switch, module, hazard, and control evidence before replacing a flasher or lamp.
Separate blade and glass conditions from fuse, switch, motor, linkage, washer, wiring, module, and frozen-system evidence while protecting visibility and the windshield.
Separate airflow, temperature, humidity, glass, control-door, blower, and cooling-system evidence before driving in conditions where the windshield cannot stay clear.
Use speed, braking, acceleration, road surface, and steering input to separate wheel/tire, brake, hub, axle, suspension, and steering causes.
Use load, speed, engine rpm, gear, and steering input to separate axle, CV-joint, driveshaft, mount, wheel/tire, transmission, and engine-performance causes.
Use steering angle, speed, throttle, braking, and road surface to separate tire, wheel, hub, bearing, CV-joint, suspension, steering, and driveline causes.
Use lamp behavior, symptoms, code status, freeze frame, readiness, and system tests to understand what the vehicle detected without treating a code as a parts order.
Separate true transmission slip or shift flare from engine power loss, traction-control intervention, clutch concerns, and normal ratio changes before condemning a transmission.
First determine whether the engine cannot make power, the transmission is not transferring it, or a chassis/control system is limiting torque.
Treat active hot coolant loss as a burn and overheating hazard, then inspect the cooled system to separate external leakage, cap/sealing concerns, trapped air, and possible internal loss.
Classify whether the engine stalls at idle, under load, during deceleration, immediately after starting, or with a broader electrical power loss before choosing a test path.
Classify smoke or a burning smell by location, color, timing, and nearby systems before attempting another drive or touching a hot component.
Cabin heat complaints can come from engine temperature, coolant level/circulation, airflow, blend-door/control operation, or an electric heat source on some vehicles.
Water inside the cabin after rain, washing, or HVAC use can come from drains, seals, glass, body openings, or condensation. Locate the path before removing trim or blaming a coolant leak.
Grinding or scraping during braking can indicate friction-material, hardware, rotor/drum, shield, bearing, or debris concerns. Braking performance and heat determine whether the vehicle should be driven at all.
Brake squeal can come from friction-surface behavior, hardware contact, contamination, temperature, or a dragging component. Separate an intermittent noise from signs of unsafe braking before choosing a repair.
A fuel-economy complaint is meaningful only after establishing a repeatable baseline and separating normal operating changes from engine, emissions, tire, brake-drag, drivetrain, or temperature-control faults.
A soft, spongy, low, or sinking pedal can reflect hydraulic leakage or air, master-cylinder or control faults, mechanical adjustment or flex, and other foundation-brake concerns. Braking safety comes before diagnosis.
Reduced braking, unusually long stopping, or a vehicle that will not stop normally is a stop-driving condition. Secure the vehicle first, then separate hydraulic, assist, friction, mechanical, and control-system evidence with qualified service information.
A pedal that suddenly feels hard or requires much more effort can indicate loss of brake assist, a vacuum/electrical control concern, or another braking fault. Secure the vehicle and verify the exact assist system before driving or replacing parts.
A wheel that locks, a brake that stays applied, or a vehicle that pulls with heat or odor can become a control and fire hazard. Stop driving and separate friction, hydraulic, parking-brake, mechanical, and control evidence with the exact vehicle procedure.
A sudden loss of steering assist, heavy steering, or a steering control change is a safety-critical handling problem. Stop safely and separate assist supply, electrical/control, hydraulic, tire, and mechanical evidence before any repair decision.
An oil-pressure warning can represent actual lubrication-pressure loss or an electrical/sensor reporting fault. Because real pressure loss can damage an engine quickly, operation safety comes before diagnosis.
Restore a safe rear-visibility workflow by separating a camera, reverse-input, power, ground, connector, display, network, or software concern before replacing a module.
Separate an intermittent radio or screen reset from a complete power loss by recording what else resets, then test supply, ground, protection, network, and heat evidence before blaming the head unit.
Treat gasoline or diesel odor as a safety signal first, then separate a liquid leak, vapor-system concern, refueling spill, exhaust odor, and cabin-source issue without running the vehicle beside an active leak.
An EVAP code identifies a monitored vapor-control condition, but the useful next test depends on whether the evidence points to a leak/sealing fault, purge-flow fault, electrical circuit fault, or an incomplete monitor.
Separate braking pull, acceleration/load-sensitive pull, tire pull, steering/suspension faults, and alignment geometry before ordering an alignment or replacing a part.
Use road speed, steering load, acceleration/coast, gear or drive mode, and tire condition to separate wheel-bearing, tire, CV/shaft, differential, axle, and other rotating-noise paths.
Describe noises, warning lights, when the problem happens, recent work, and any scan codes. IAR search can route the evidence to a guide; the AI assistant can organize a test plan when the static library does not cover the exact wording yet.
Read the urgency first, then choose a measured procedure that explains what the result can—and cannot—prove.