P0512 – Starter Request Circuit

P0512 means the ECU has detected a malfunction in the Starter Request Circuit — the electrical pathway that carries the “start engine” signal from the ignition switch or push-button start module to the starter relay and ECU. When this circuit fails, the ECU may not receive the start request, resulting in no-crank conditions, intermittent starting, or delayed starter engagement. In this guide, you’ll learn exactly what P0512 means, how it works, the common causes behind it, real-world examples, and the diagnostics and repairs that reliably resolve this fault.

What Does P0512 Mean?

P0512 sets when the ECU doesn’t detect the expected voltage or signal state on the starter request input line during a start command. In traditional key-start systems, this signal comes from the ignition switch. On modern vehicles with push-button start, the signal comes from a body control module (BCM) or smart-key module. If the ECU doesn’t see the correct voltage when the driver requests a start, it interprets this as a circuit fault and stores P0512.

A failure in this circuit can prevent the starter relay from energizing, causing the engine not to crank. Wiring issues, corroded connectors, ignition switch wear, BCM faults, or relay problems can all lead to this code.

Quick Reference

  • OBD-II Family: P-Code (Powertrain)
  • Scope: Generic
  • System: Starter Request / Crank Signal
  • Difficulty Level: Moderate
  • Estimated Repair Cost: €40–€250
  • Last Updated: 2025-11-24

Real-World Example / Field Notes

A common cause of P0512 on Chrysler, Dodge, and Jeep models is a worn ignition switch or a failing WIN (Wireless Ignition Node) module failing to send a proper start request signal. One Dodge Charger case involved intermittent no-crank conditions with P0512 set each time. The ignition switch provided incorrect voltage under load, causing the ECU to miss the signal even though the key turned normally. Replacing the switch fixed the issue. On push-button Hyundai and Kia models, a failing brake-switch signal can prevent proper starter request, triggering P0512 even though the starter is functional.

Symptoms of P0512

  • No-crank condition: Engine does not turn over when starting.
  • Intermittent starting: Sometimes cranks, sometimes doesn’t.
  • Delayed starter engagement: Crank begins only after several attempts.
  • Starter clicks but doesn’t engage: Weak or inconsistent signal to the relay.
  • Dashboard lights flicker at start: Poor signal or voltage drop.
  • Check Engine Light: P0512 often appears with no-crank complaints.

Common Causes of P0512

Most Common Causes

  • Faulty ignition switch (key systems).
  • Worn or failing starter relay.
  • Broken or corroded wiring in the starter request circuit.
  • Poor ground or low battery voltage affecting the request signal.
  • Push-button start module / BCM failing to send crank request.

Less Common Causes

  • Faulty clutch or brake pedal switch (prevents starter request).
  • ECU internal fault preventing detection of start signal.
  • Security system / immobilizer blocking crank request.
  • Aftermarket alarm or remote-start system interfering with signal.
  • Water intrusion in ignition or BCM connectors.

Diagnosis: Step-by-Step Guide

Begin by confirming whether the ECU is receiving the start signal and checking the ignition or start module.

Tools You’ll Need: OBD-II scanner, multimeter, test light, wiring diagram, battery tester, and access to the starter relay.

  1. Check battery voltage first. Low voltage can cause false circuit faults.
  2. Scan for related codes. Look for immobilizer, BCM, or brake-switch faults.
  3. Monitor live data. Many vehicles show “Start Request: Yes/No” — confirm if the ECU sees your command.
  4. Test ignition switch output. Key-start systems should output 12V on the start wire when turned to “crank.”
  5. Check brake or clutch pedal switch. Required for start — a failed switch blocks the request.
  6. Inspect starter relay. Check for proper power, ground, and switching voltage.
  7. Check for wiring damage. Look at harnesses near the steering column, BCM, and relay box.
  8. Test for voltage on the ECU starter request pin. No voltage = switch/wiring issue; voltage but no crank = relay/output issue.
  9. Check immobilizer status. If IMMO is active, the ECU may block the starter request.
  10. Inspect push-button start module. Confirm brake pedal signal and request output are correct.

Pro Tip: If the engine cranks normally when bypassing the starter relay, but P0512 remains, the problem is almost always in the request signal path — ignition switch, pedal switch, or BCM output.

Possible Fixes & Repair Costs

  • Replace ignition switch: €60–€150 and very common on older models.
  • Replace starter relay: €10–€40.
  • Repair wiring or connectors: €10–€80 depending on location.
  • Replace brake/clutch switch: €15–€50.
  • Repair or replace BCM / start module: €120–€250.
  • Fix grounding or battery issues: €0–€40.
  • Reprogram key or immobilizer: €30–€120 if the system blocks crank request.

Always confirm whether the ECU is receiving the start request before replacing parts — this distinguishes between ignition-side failures and relay/starter-side issues.

Can I Still Drive With P0512?

If the vehicle still starts, you may be able to drive temporarily — but intermittent no-crank conditions can leave you stranded without warning. If the engine doesn’t crank at all, the car is not drivable. Fix P0512 promptly to avoid unpredictable starting failures.

Related Codes

  • P0574 – Cruise Control System Vehicle Speed Too High
  • P0573 – Brake Switch “A” Circuit High
  • P0572 – Brake Switch “A” Circuit Low
  • P0571 – Brake Switch “A” Circuit
  • P0570 – Cruise Control Accelerate Signal
  • P0569 – Cruise Control Coast Signal
  • P0568 – Cruise Control Set Signal
  • P0567 – Cruise Control Resume Signal
  • P0566 – Cruise Control Off Signal
  • P0565 – Cruise Control On Signal

Key Takeaways

  • P0512 indicates the ECU is not receiving a correct starter request signal.
  • Common causes include a bad ignition switch, faulty relay, wiring issues, or BCM/push-button faults.
  • The vehicle may fail to crank or start intermittently.
  • Live data and voltage testing quickly reveal which part of the start-request path is failing.

FAQ

What causes P0512 most often?

Most commonly a worn ignition switch, faulty brake/clutch switch, or wiring problem preventing the start-request signal from reaching the ECU.

Does P0512 mean my starter is bad?

No. P0512 refers to the start-request signal, not the starter motor itself. The engine may not crank because the signal never reaches the starter relay.

Can a push-button start system trigger P0512?

Yes — if the BCM or brake pedal switch doesn’t send a valid start request, the ECU will store this code and prevent cranking.

Can I drive with P0512?

Only if the engine still starts consistently. If starting becomes intermittent or fails entirely, the vehicle should not be driven until diagnosed.

How do I diagnose P0512?

Check ignition switch output, brake/clutch switch operation, starter relay function, wiring continuity, and whether the ECU is receiving the start-request signal in live data.