P0205 — Injector Circuit/Open - Cylinder 5

Quick answer

• What it means: The Powertrain Control Module (PCM) has detected an electrical problem with the fuel injector circuit for cylinder 5.
• Severity: Get towed or repair immediately; prolonged driving can cause severe engine damage.
• Most common cause: A faulty fuel injector or a wiring problem leading to the injector.

What the P0205 code means

The official OBD-II definition for P0205 is "Injector Circuit/Open - Cylinder 5." In simpler terms, your car's computer (the PCM) has identified an open circuit or an abnormal electrical signal within the wiring or the fuel injector itself for the fifth cylinder. This means the PCM is not able to properly control the fuel delivery to that specific cylinder, which can lead to misfires, poor engine performance, and potentially unburned fuel entering the exhaust system.

Common symptoms

• Check Engine Light illuminated
• Engine misfires or runs rough
• Poor acceleration or reduced engine power
• Engine hesitation or stalling
• Increased fuel consumption
• Rough idle
• Potential smell of raw fuel from the exhaust
• Engine knocking or pinging sounds

Common causes

1. Faulty Fuel Injector: The injector itself may have an internal electrical short or an open circuit preventing it from operating correctly. This is the most common cause.
2. Wiring Harness Issues: Damaged, corroded, or open wiring leading to the cylinder 5 fuel injector. This can include frayed wires, poor connections at the injector or PCM, or rodent damage.
3. Bad PCM Driver: Less common, but the fuel injector driver circuit within the PCM could be faulty, failing to send the correct signal to the injector.
4. Poor Electrical Connection: A loose or corroded connector at the fuel injector or at the PCM can disrupt the electrical flow.
5. Carbon Buildup: Excessive carbon buildup around the injector tip can sometimes affect its operation, though this is more likely to cause a P030x misfire code first rather than a circuit open code.

How a technician diagnoses it

1. Verify the Code and Freeze Frame Data: The technician will connect an OBD-II scanner to confirm the P0205 code and review freeze-frame data. This data shows engine conditions (RPM, engine load, temperature, etc.) at the moment the code was set, providing crucial clues.
2. Visual Inspection: A thorough visual inspection of the wiring harness leading to the cylinder 5 fuel injector will be performed, checking for any signs of damage, corrosion, or loose connections. The injector itself will also be inspected for any obvious physical damage.
3. Electrical Testing at the Injector:
   • Resistance Test: The technician will disconnect the injector and measure its electrical resistance (ohms) across its terminals using a multimeter. A typical good injector will have a resistance between approximately 10 to 18 ohms (varies by manufacturer). A reading of infinite resistance (open circuit) or a very low resistance (short circuit) indicates a faulty injector.
   • Voltage Test: With the engine cranking or running, the technician will check for power (usually battery voltage, 12V) at one of the injector