Injectors need both an electrical supply and ECU control.
Why this matters
If all injectors lose command at once, a shared cause such as ECU power, immobilizer, crank signal, or common feed is more likely than every injector failing simultaneously.
An injector can receive a command yet still be mechanically clogged or stuck.
First checks
• Check injector fuse/relay power where applicable.
• Use a noid light only when compatible with the circuit.
• Use scan data and oscilloscope testing for advanced diagnosis.
• Check whether immobilizer or missing crank signal would inhibit injection.
A practical test path
Begin with the easiest observation that can divide the problem into two paths. In a injector command complaint, do not change several things at once. Record the initial condition, perform one test, and then decide what the result proves. If the test shows normal power, move downstream. If it shows a loss, stay with that part of the circuit until the source of the loss is found. Whenever possible, test the circuit while it is carrying its normal load rather than relying only on resistance or continuity checks with everything switched off.
For a crank-no-start, use scan data and direct tests to determine which basic requirement is missing. Normal starter speed does not prove the engine computer has a valid position signal, correct fuel pressure, ignition output, authorization, or compression.
Common mistakes to avoid • Using a conventional test light on sensitive ECU driver circuits.
Stop and get help when… • Never pierce sealed wiring unnecessarily; use proper back-probing or breakout methods.
What to record
Write down whether the symptom was present during the test, the battery voltage or scan values you observed, and exactly what changed. For injector command, include temperature, key used, whether the engine cranked, and any warning or security indicators that were different from normal. Good notes prevent repeated testing and make professional diagnosis faster if you need it.