Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsStarting System Diagnosis and RepairMedium
A technician is diagnosing a 'no-crank' condition on a vehicle equipped with a remote start system. The engine starts normally when using the remote start, but fails to crank when using the ignition key. What is the most likely cause?
- AA discharged battery.
- BA faulty starter motor.
- CAn open circuit in the main power cable to the starter.
- DA faulty ignition switch.
Show answer & explanationAnswer & explanation
Correct answer: D. A faulty ignition switch.
If the remote start system can successfully crank and start the engine, it confirms that the battery, starter motor, and main power/ground cables are all functional. This isolates the problem to the components unique to the key-start circuit, primarily the ignition switch and its associated wiring to the starter solenoid.
Why the other options are wrong
- A. A discharged battery would prevent both remote and key starting.
- B. If the starter motor was faulty, remote start would also fail.
- C. An open in the main power cable would prevent both remote and key starting.
Remote Start vs. Key Start Diagnosis
Using the functionality of a remote start system to isolate starting circuit problems, by differentiating between components common to both systems and those unique to the key-start path.
- If remote start works, battery, starter motor, and main cables are good.
- Problem is then in the key-start control circuit (ignition switch, neutral safety switch, starter relay wiring).
- Simplifies diagnosis by eliminating major power components.
Memory trick: Remote works, key doesn't, follow the path, find the culprit's presence.