P0512

P0512 means the ECM saw the starter request input go active when conditions don't allow a crank event (transmission not in Park/Neutral, brake not pressed on push-button systems, key-position mismatch, or the request line stuck logically high). The starter request circuit is a discrete input to the PCM/BCM, typically pulled low at rest and driven to battery voltage when the START position is commanded — so a scan-tool live data PID of 'Starter Request Input' should read 0V key-on engine-off and snap to 10-12V only during the brief crank command. Shop-floor ladder, cheapest first: scope the start signal at the PCM input pin during a crank attempt — if it sits above ~1V at rest, you've got a shorted-to-power wire or a stuck ignition switch contact (GM tilt-column passive-key vehicles in particular wear the START contacts and bridge them intermittently). Next check is the ignition switch / push-button assembly itself — ohm the START position contacts cold and after a 20-minute heat soak, because the failure is almost always thermal. Wiggle-test the harness between the column and the BCM with the scan tool watching the PID; intermittent transitions while flexing the harness are a chafed wire. Expensive-misdiagnosis caveat: don't replace the BCM or PCM on P0512 until you've physically disconnected the ignition switch and confirmed the start-request input drops to 0V at the module pin — a stuck switch will frame the module as faulty and burn a $400-700 part for a $90 switch problem.

Vehicle-specific patterns: 2005-2010 GM passive-key vehicles (Cobalt, HHR, Malibu, Equinox, G6) running the recall-era column ignition switch frequently throw P0512 from the documented ignition-switch wear that GM addressed in the 2014 recall — the start contacts bridge to RUN as the cylinder ages, sending the start request to the BCM even after the key snaps back. 2010-2017 Ford Mustang and F-150 with push-button start commonly throws P0512 from a failing brake-pedal position switch or from the push-button assembly itself bouncing the request line — Ford service info covers both diagnostics. 2008-2013 Cadillac CTS / SRX with keyless ignition throws P0512 from BCM software that misinterprets a key-FOB authentication retry as a duplicate start request — a TIS2WEB reflash from the dealer clears it. 2011-2016 Chrysler 300 / Charger / Durango with the WIN module (wireless ignition node) commonly throws P0512 from WIN-module solder-joint cracks that intermittently float the start line. Estimated repair: $90 (ignition switch DIY) to $750 (BCM/WIN module replacement + programming).