OBD-II trouble code
P0512: Starter Request Circuit
The circuit that asks for a crank is faulty — the module either never received a valid start request, or received one it could not act on. This is a no-crank code, not a running-engine code.
Quick facts
- System
- Powertrain
- Category
- Starting System
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $25 – $900
- DIY difficulty
- Intermediate DIY
What does P0512 mean?
P0512 belongs to a different moment in the vehicle's life than almost every other code in the P05xx range. Nothing here concerns how the engine runs. It concerns the few hundred milliseconds between you asking for a start and the starter actually turning, and it sets when the request circuit carrying that ask does not behave the way the module expects.
On a modern vehicle the starter is not wired straight to the key. You make a request — turning a key barrel or pressing a button — and that request travels to a module, which decides whether to grant it and then energizes the starter relay. The powertrain control module is one of the gatekeepers in that chain, and it will refuse the request if the transmission range input does not read park or neutral, if the brake pedal switch has not confirmed on an automatic or the clutch switch on a manual, or if the immobilizer has not authorized the key. When the module sees a request it cannot honour, or sees the request line in an implausible state, P0512 is stored.
The useful consequence of that chain is that the code often has nothing to do with the starter itself. A transmission range switch that has drifted out of adjustment is a genuinely common cause: mechanically the shifter is in park, electrically the module never gets a clean park signal, and a perfectly healthy starter never gets asked to do anything. The same is true of a brake pedal switch pushed out of position, which is worth suspecting immediately if your brake lights also behave oddly.
On push-button start systems the request originates in the body control module and travels over the vehicle network, so P0512 frequently arrives with communication codes beside it. That pairing is diagnostically valuable — if U-codes are stored alongside, the problem is the message not arriving rather than the request circuit being broken, and the network fault is what to chase.
Treat this as a code that can strand you. The engine may run fine right now, but the fault lives in the path that restarts it, and an intermittent P0512 has a habit of becoming a permanent one in a parking lot rather than in a driveway.
Common causes
- Failed or intermittent starter relay
- Transmission range switch out of adjustment or failing, so park or neutral is never confirmed
- Brake pedal switch on automatics, or clutch position switch on manuals, out of adjustment or failed
- Corroded or damaged wiring in the start request circuit
- Ignition switch electrical section worn
- Push-button start request not reaching the PCM because of a network communication fault
- Immobilizer or anti-theft system withholding authorization
- Body control module fault on vehicles where the request originates there
Symptoms
- Engine does not crank at all when you turn the key or press the button
- Intermittent no-crank that clears if you cycle the key or reselect park
- Cranks only when the shifter is jiggled or moved into neutral
- Dash message such as press brake to start, or a start request that is simply ignored
- Check engine light on with P0512 stored
- A single relay click, or no sound at all, when a start is requested
- Communication codes stored alongside on push-button start vehicles
Diagnostic steps
- 1.Confirm the battery is healthy and the terminals are clean before anything else. Low system voltage produces no-crank symptoms that look identical to a circuit fault and will mislead every test that follows.
- 2.Try starting with the shifter in neutral instead of park. If it cranks in neutral but not in park, the transmission range switch or its adjustment is the fault and the starter is fine.
- 3.Watch the transmission range and brake switch inputs in live data while you move the shifter and press the pedal. Each should change state cleanly and match what you are actually doing.
- 4.Swap the starter relay with an identical relay elsewhere in the fuse box and retry. It is a two-minute test that resolves a meaningful share of these codes.
- 5.Scan every module, not just the engine module. Communication codes stored beside P0512 on a push-button vehicle redirect the diagnosis to the network rather than the start circuit.
- 6.Measure voltage at the starter solenoid trigger wire while a start is requested. Voltage present with no crank moves the fault to the starter itself; no voltage keeps it in the request circuit.
Repair cost
$25 – $900
A starter relay is $10-$35 and often the whole fix. Brake pedal switch replacement runs $80-$180 installed. A transmission range switch is $150-$400 depending on whether it sits externally on the transmission case or requires dropping the pan. Ignition switch electrical sections are $200-$450. Body control module replacement with programming is the top of the range at $500-$900 and is uncommon. Note that the starter itself is frequently not the repair despite the symptom.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with starter replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.