What it means
The PCM detected an open or electrical fault in the cylinder 3 injector A circuit. The code does not establish that the ECU disables the injector or that a misfire code will also set.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The PCM switches the cylinder 3 injector's electrical circuit to control fuel delivery. P0203 means it detected an open or other electrical fault in the cylinder 3 injector A circuit; it does not alone confirm that fuel delivery has stopped or that a misfire code will be stored.
Common causes
Most likely first.
- Injector winding failed open
- Wiring or connector fault
Symptoms
- Check-engine light
- Rough running or engine misfire
- Reduced engine power
- Hard starting or stalling
How to diagnose it
- Save freeze-frame data and scan for cylinder 3 misfire or related circuit codes to see when the fault appeared and whether it is isolated to that cylinder.
- Find cylinder 3 using the vehicle's cylinder identification information and inspect its injector connector and wiring for corrosion, looseness, chafing, or heat damage.
- Check the cylinder 3 injector connector fit and measure the injector winding against the manufacturer's specification.
- Follow the wiring diagram to test the cylinder 3 injector supply and control circuits for opens, shorts, and poor connections.
- If the injector and circuit are sound, have the PCM's cylinder 3 injector driver tested.
Common fixes
- Reconnect or clean the cylinder 3 injector connector.
- Repair chafed or broken wiring in the cylinder 3 injector circuit.
- Replace the cylinder 3 injector if electrical testing confirms a winding fault.
- Repair or replace the PCM if its cylinder 3 injector driver is proven faulty.
Can I keep driving?
Do not continue driving if the engine is misfiring, stalling, or losing power; these symptoms can worsen and may increase emissions. If it runs normally, keep driving to a minimum until the cylinder 3 circuit is diagnosed.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.