OBD-II Code P1200 — What It Means & How to Fix It

What Does This Error Mean?

P1200 indicates a fault in the fuel injector circuit or the PCM power relay. The PCM has detected that it cannot properly control one or more fuel injectors. This can prevent the engine from starting, cause rough running, or trigger a no-start condition. Common on Toyota, Honda, and Nissan vehicles, where injector relay circuits are closely monitored.

Affected Models

Common in Toyota Corolla, Camry, and RAV4
Common in Honda Civic, Accord, and CR-V
Common in Nissan Altima and Frontier
Common in Mazda 3 and Mazda 6

Common Causes

Faulty PCM power relay preventing proper voltage supply to the injector circuit
Damaged or corroded wiring in the fuel injector harness
Shorted or open fuel injector coil winding
Blown fuse supplying power to the injector circuit
Faulty PCM causing incorrect injector control signals

How to Fix It

Check the fuse box for any blown fuses related to the fuel injection or ECU power circuit.

Refer to the owner's manual fuse diagram. Replace any blown fuse and see if the code returns.
Locate the PCM power relay and test it. Swap it with an identical relay from another circuit to see if the code clears.

A faulty relay is one of the most common causes of P1200 and is an inexpensive fix.
Inspect the wiring harness at each fuel injector connector for corrosion, damage, or loose pins.

Pay close attention to areas where the harness bends or passes near hot engine components.
Use a multimeter to test injector resistance at each connector. Compare readings to the manufacturer specification.

Most injectors measure 12–17 ohms. A reading far outside this range indicates a failed injector.
Clear the code with a scan tool and perform a test drive. If P1200 returns, professional diagnosis of the PCM and injector driver circuit is needed.

A faulty injector driver inside the PCM requires PCM replacement or specialist repair.

When to Call a Professional

Injector circuit diagnosis requires a wiring diagram and a multimeter. PCM relay replacement is $20 to $80. Fuel injector replacement runs $100 to $300 per injector. If the PCM itself is faulty, replacement and programming can cost $500 to $1,500.

Frequently Asked Questions

Will P1200 prevent my car from starting?

It can. If the injector relay or power circuit is completely failed, the injectors will not open and the engine will crank but not start. In many cases the car will still run but roughly, with misfires and poor fuel delivery.

Is P1200 the same on all car brands?

No. P1200 is a manufacturer-specific code, so its exact meaning varies by brand. On Toyota it typically points to the injector circuit relay. On Honda it may indicate a different injector driver issue. Always check the definition for your specific make.

Can a bad ground cause P1200?

Yes. A poor engine ground or chassis ground can create voltage irregularities that confuse the PCM. Always inspect ground straps and connections as part of diagnosing any injector circuit code.