What does it mean?
P1200 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Fuel Injector Circuit Malfunction .
Symptoms
- Check engine light on, often with misfire codes alongside
- Rough idle and vibration, with the engine shaking at a stop
- Loss of power, hesitation and poor acceleration
- Hard starting or a long crank before the engine fires
- Fuel smell from the exhaust and a raw fuel smell in some cases
- Higher fuel consumption and possible black smoke
Likely causes
- Open or shorted injector winding
- Broken, chafed or corroded injector harness wiring, often at the connector where it flexes with the engine
- Injector connector loose, corroded or with a pushed-back terminal
- Blown fuse or failed relay in the injector power supply
- Poor injector power feed from a corroded splice shared by several injectors
- Failed injector driver stage inside the control module
- Wrong or high-resistance aftermarket injectors overloading the driver
How to fix it
- Read all stored codes; injector codes together with cylinder-specific misfire codes narrow the search quickly
- Check the injector supply fuse and confirm battery voltage at each injector connector with the ignition on
- Measure the resistance of each injector winding and compare all cylinders against each other and the specification
- Use a test light or scope on the control wire to confirm the module is switching each injector
- Inspect connectors for corrosion, spread terminals and heat damage; wiggle-test the harness with the engine running
- Repair damaged wiring and clean or replace terminals
- Replace the faulty injector only after the circuit and driver test good, then clear codes and confirm smooth running