Electrical and sensors

P1500 — Starter Signal Circuit Malfunction

Severity: medium Drive with care, to a shop

What P1500 means

P1500 is a manufacturer-specific code, so its meaning varies by brand. It is most often tied to the starter request signal circuit between the ECM, ignition switch and starter relay. The ECM expects a certain voltage when you turn the key or press start, and sets the code if the signal is missing, erratic or out of range.

Symptoms

  • Engine does not crank
  • Clicking at the starter or relay
  • Hard starting
  • Intermittent no-start
  • Check engine or security light on

Possible causes

  1. Failed starter relay
  2. Corroded or damaged wiring and connectors at the starter
  3. Worn ignition switch contacts or start button
  4. Weak battery or poor ground
  5. Security system blocking the start
  6. ECM starter driver fault

How to diagnose

  1. Scan all codes and freeze frame data, looking for immobilizer faults
  2. Test battery voltage and inspect terminals and grounds
  3. Inspect starter and relay wiring and connectors for corrosion or breaks
  4. Check starter fuses and swap in a known-good relay
  5. Measure the signal voltage on the control wire while turning the key
  6. Check continuity and resistance of the wire from ignition switch to relay and ECM
  7. Verify the immobilizer and key are working
  8. If the circuit tests good, test the ECM per the factory wiring diagram

Common fixes

  • Replace the starter relay
  • Repair or replace wiring and connectors
  • Replace the ignition switch or start button
  • Charge or replace the battery, clean terminals and grounds
  • Fix the immobilizer fault or reprogram the key
  • Repair or replace the ECM as a last resort

P1500 on different brands

Lexus · manuals
On Lexus, this code points to a starter signal circuit malfunction, meaning the control module detected improper operation of that circuit.

Questions and answers

Why do I get P1500 and no crank?

Usually the start request signal isn't reaching the starter. The relay, ignition switch contacts, wiring or an immobilizer lockout are common culprits. Start with the battery and relay.

Can I drive with P1500?

If the car starts reliably, yes, but a no-start could happen at any time. Check the relay and wiring soon.

Does P1500 mean the same thing on every brand?

No, it is manufacturer-specific. On Lexus it refers to the starter signal circuit, while other makes may define it differently, so check the documentation for your vehicle.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.