Error Code P0512 is defined as Starter Request Circuit, meaning there’s a malfunction going on the starter’s request.
This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system or those made since 1996 up to present. It’s particularly common among Chrysler, Dodge, Hyundai, Jeep, Mazda, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
The battery supplies a constant voltage to the starter through the positive cable. The starter requests signal from the ignition switch. When the ignition key is placed into the ignition cylinder and turned to start position, it actuates the electrical portion of the ignition switch and closes a set of heavy-duty contacts, which completes the starter request circuit. Once completed, a battery voltage signal is sent to the starter solenoid (or the starter relay on some models).
When the starter signal is received by the starter solenoid, the starter motor starts to spins, and a small cog will be pushed in the direction of the engine where the teeth of the cog intermesh with the teeth of the flywheel ring gear. This process will turn the engine crankshaft, which will then initiate the engine startup.
For vehicles with Error Code P0512, it means the PCM has probably not received the starter request signal.
If the engine can still be cranked normally, then be addressed at your convenience. Obviously though, if the engine fails to start, then you would have to address the code as soon as possible to be able to use the vehicle. In some minor cases, there may be no symptoms at all. However, common symptoms of this code include:
- Engine fails to start
- Delayed starter engagement (startup requiring multiple key cycles)
Other PCM power circuit failure codes or ignition system circuit failure may also be present.
- Defective ignition switch
- Defective starter relay
- Burnt fusible links
- Blown fuses
- Open or shorted circuits in the starter request circuit
- Defective or programming error in the PCM
How to Check
Start with a visual inspection of the related connectors and wirings. If possible, you can swap the starter relay with a known good relay, since most manufacturers use an identical relay for multiple functions. If the problem is solved by swapping the relays, then swap them back and replace the starter relay with a new one.
You can also test the relays without swapping by looking into your vehicle information source and finding the starter system wiring diagram. Check the starter relay connector view; test the battery voltage input circuit to the starter relay. This circuit must keep a battery voltage when the ignition switch is placed in the On position (switched voltage). If you found no voltage being put into the starter relay, then the system fuses must be checked, along with fusible links, and wirings from the battery or battery junction box.
In most cases, the ignition switch will provide relay secondary voltage source signal when the ignition switch is turned to the start position. Simultaneously, the PCM will provide a ground signal to the starter relay. The secondary voltage and ground signals will cause contacts inside the relay to close, completing the starter request circuit that should send a signal to the starter solenoid and back to the PCM.
Use a DVOM (digital volt-ohmmeter to test the circuit for resistance. Make sure you disconnect all connected and related controllers before doing the testing. First, test the voltage signal to the relay, from the ignition switch first. If there’s none, then there must be a defective ignition switch or malfunction in the wiring.
If there is a secondary input present, then check the ground signal input from the PCM. If there’s no ground being input to the starter relay coming from the PCM, then there may be a failed PCM problem or a programming error problem with the PCM.
How to Fix
- Replacement of starter relay
- Repair or replacement of defective ignition switch or wiring malfunction
- Replacement or reprogramming of PCM
Additional diagnostic notes:
This code rarely shows up in vehicles without a starter relay.
Avoid misdiagnosis by performing repairs and clearing the codes as you progress. Use the vehicle normally until the PCM either enters readiness mode, or the code is reset.
Before swapping the relays during diagnosis, make sure they have matching service numbers. And always swap relays back to their original position and only replace the defective relay with a new one.