What this test is for
Build a safe, repeatable evidence set for a normal-crank/no-start complaint without treating one code, sound, or test result as a failed part.
Use the procedure to narrow a cause group. The result must be interpreted against the exact vehicle, equipment, and conditions.
- 01PurposeBuild a safe, repeatable evidence set for a normal-crank/no-start complaint without treating one code, sound, or test re
- 02PrepareOBD-II scanner or scan tool / Battery tester or digital multimeter
- 03MeasurePreserve the no-start condition / Capture complete scan evidence
- 04InterpretA changed condition can hide the branch that actually needs testing; normal rotation alone does not prove the battery or
- 05ContinueBattery voltage and condition test / Voltage-drop test
Follow the sequence, stop when evidence changes the path, and verify the exact vehicle information before acting.
Preserve the operating conditions, equipment setup, and result before moving to the next branch.
Tools and preparation
- OBD-II scanner or scan tool
- Battery tester or digital multimeter
- Approved ignition and fuel test equipment
- Exact service information
Procedure and interpretation
Preserve the no-start condition
Record cranking sound and speed, warning lamps, security messages, fuel odor, smoke, recent work, temperature, and whether the symptom changes when cold or warm.
The original operating pattern is documented before repeated attempts or parts are moved.
A changed condition can hide the branch that actually needs testing; normal rotation alone does not prove the battery or control inputs are adequate.
Capture complete scan evidence
Save stored, pending, and permanent codes, freeze frame, engine-speed data, synchronization or authorization status when supported, and relevant power-supply faults before clearing anything.
The scan record preserves the conditions and module evidence associated with the failed start.
A code identifies a monitored condition or circuit, not automatically a failed sensor, coil, injector, pump, or module.
Confirm cranking power and speed
Use the approved battery and voltage-drop procedure while the engine cranks, and compare the result with exact vehicle and equipment limits.
Battery, cables, grounds, and cranking behavior meet the applicable test boundary.
An engine can sound as if it turns normally while unstable voltage or speed prevents valid control, ignition, or injection.
Test the missing combustion requirement
Use approved methods to establish whether ignition energy, injector command, fuel delivery, air control, and synchronization are present under the actual no-start condition.
At least one evidence-backed branch is separated from the others without unsafe improvisation.
A missing result narrows the path; it does not identify which upstream circuit or component caused it.
Evaluate mechanical condition only when indicated
If electrical, authorization, ignition, fuel, and control evidence does not explain the symptom, use the exact compression, relative-compression, leak-down, vacuum, or timing procedure for the engine.
Mechanical evidence is measured with the correct setup and limits rather than inferred from sound alone.
Mechanical testing is a branch chosen by evidence, not a reason to replace internal parts from a no-start symptom.
Verify the original starting conditions
After the supported fault is corrected, repeat the relevant cold, warm, load, key, and recent-work conditions and confirm codes and data remain appropriate.
The engine starts consistently and the original no-start pattern does not return.
One successful start does not prove the repair if the enabling condition has not been reproduced.
Record this test result
Save a bounded result and note to the selected vehicle. This is a personal record, not a verified diagnosis.
Choose a vehicle in My Garage or the vehicle selector first. IAR will not attach a test result to an unknown vehicle.
What to test next
Safety boundary
Fuel, ignition, and moving-parts safety
Work in a ventilated area, keep sparks and flames away from fuel vapors, and use only approved test equipment. Do not bypass immobilizers, spray unapproved starting fluid, or reach near belts and fans during a start attempt.