How is fault code P0512 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Load test the battery and check the terminals before anything else. A reading of at least 12.5 to 12.6 volts at rest is what you want, and clean tight connections matter as much as the voltage figure 2. Scan for stored codes and note anything immobiliser or ignition related sitting alongside the P0512, because that often points you straight at the cause 3. Pull and check the relevant fuses and fusible links for the starter and ignition circuits 4. Go over the wiring, connectors and terminals in the starter request circuit looking for green corrosion, chafing, or a plug that's worked loose 5. Swap the starter relay with a matching one from another circuit, or test it for continuity and voltage against the wiring diagram 6. Confirm the ignition switch is doing its job and, on cars with an immobiliser, check the antenna ring around the barrel and the key fob battery

Starter Request Circuit

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Load test the battery and check the terminals before anything else. A reading of at least 12.5 to 12.6 volts at rest is what you want, and clean tight connections matter as much as the voltage figure 2.

PPowertrain
0Generic code
5Speed / Idle
12Sequence number

What does it mean?

We’ve certainly come a long way since starting our cars with a hand-crank, moving through push-button ignition and all manner of keyed ignitions. In the interest of security, it was found that even intricate and hard-to-duplicate mechanical keys weren’t enough to prevent unwanted engine starting, leading to the development of the engine immobilizer system.

Then, mechanical keys were paired with specialized resistors and uniquely-coded radio transponders, even in in modern push-button ignition systems. Just as keys need to be cut or “programmed” to match the vehicle ignition cylinder, the engine immobilizer system needs to be programmed to recognize the transponder.

Basically, the immobilizer uses a small antenna to detect the appropriate transponder signal when engine start is requested, either by turning the physical key to the start position or when the driver steps on the brake and presses the start-stop button. If the engine immobilizer system recognizes the transponder, it enables the fuel and ignition system and the starter. If not, it locks out the starter or the engine control module (ECM), making the vehicle impossible to drive.

In some cases, the engine immobilizer system, which may or may not be part of the ECM, may have a hard time recognizing the transponder, even if it is properly registered. In this case, the engine immobilizer system, may lock out the ECM or starter, set a diagnostic trouble code (DTC), P0512 “Starter Request Circuit,” or illuminate the malfunction indicator lamp (MIL).

Symptoms

Likely causes

How to fix it

Codes From the Same System

All Fault Codes

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.