P0201 Code: Injector Circuit/Open — Cylinder 1
Last reviewed May 2026 · Reviewed by the Find This Code Editorial Team
Quick Answer
The ECU detected a fault in the fuel injector circuit for cylinder 1 — the injector may not be firing or the circuit is open.
At a Glance
What this code means
The fuel injector injects a precise pulse of fuel into the cylinder. P0201 means the ECU detected an open circuit or failure in the injector circuit for cylinder 1. This can mean the injector isn't firing at all, causing a cylinder misfire. It will often appear alongside a P0301 (cylinder 1 misfire) code.
Common causes
- Faulty fuel injector (open internal coil)
- Damaged or corroded injector wiring harness
- Open circuit in the injector power or control wire
- Failed injector driver circuit in the ECU (rare)
- Loose or corroded injector connector
Symptoms you might notice
- Check engine light on
- Cylinder 1 misfire (rough idle, engine shake)
- Possible P0301 misfire code alongside P0201
- Reduced power and fuel economy
- Rough idle especially at cold start
Can you still drive?
With caution and only short distances. A non-firing injector means a constant cylinder misfire, which can damage the catalytic converter.
How serious is this code?
High. A cylinder not receiving fuel runs a constant misfire. Extended driving will destroy the catalytic converter.
Before you replace parts
Parts replacement is often not the first step. Before buying anything, it's worth checking these basics:
- Use a noid light before buying an injector — if the noid light flashes, the circuit is fine and only the injector needs replacement; if it doesn't flash, find the wiring fault first
- Test injector resistance with a multimeter — if it matches spec, the injector coil is intact and the problem is likely wiring or the ECU driver
How to troubleshoot it
- Inspect the cylinder 1 injector connector for damage, corrosion, or disconnection
- Use a noid light — plug it into the injector harness and watch for it to flash when cranking. If it flashes, the circuit is good; replace the injector
- Test injector coil resistance with a multimeter — compare to specification (typically 12–16 ohms). An open circuit (infinite resistance) means a failed injector
- Check for wiring breaks from the injector back to the ECU
- If noid light doesn't flash, trace the wiring fault toward the ECU
Common mistakes to avoid
These are the most frequent diagnostic errors when dealing with P0201. Avoiding them can save time and money.
- Replacing the injector immediately without testing it for resistance, balance rate, and spray pattern
- Not checking the injector wiring harness and connector for shorts or opens before replacing the injector
- Confusing a faulty injector with an ignition misfire — always check for companion P030x codes
- Ignoring injector o-ring leaks that can cause fuel to bypass the combustion chamber and trigger fuel-related codes
Tools that may help
These are the types of tools commonly used when diagnosing this code. Having the right tool can save time and help confirm a diagnosis before spending money on parts.
- Noid light set
- Multimeter
- OBD-II scanner
Estimated repair cost range
Fuel injector replacement (one): $100–$250 for the part. Professional injector service: $150–$350. ECU diagnosis: $100–$200.
Costs vary significantly by vehicle, location, and whether you use OEM or aftermarket parts. These are general ranges for reference only.
When to call a mechanic
If you've completed the basic troubleshooting steps and the code keeps returning, or if you don't have access to the proper diagnostic tools, it's worth consulting a professional. A qualified technician can perform a full diagnosis and confirm the root cause before any parts are purchased. When in doubt, get a professional opinion — it can save you from an expensive misdiagnosis.
Real-world note
The noid light test is the most important diagnostic step for P0201 — it quickly tells you whether the problem is in the circuit (no flash) or the injector itself (flash present, but injector still faulty mechanically).
Learn more
How we write these guides
Find This Code guides are written based on OBD-II specification documentation, established automotive diagnostic practices, and real-world patterns observed across vehicle makes and models. Content is reviewed for accuracy and plain-English clarity before publication. Pages are marked with a “Last reviewed” date and updated when diagnostic guidance or code interpretation changes. All content is educational — it is not a substitute for hands-on diagnosis by a qualified mechanic.
Last reviewed May 2026 · Find This Code Editorial Team · Editorial standards →
Sources & references
Our guides are written based on OBD-II specifications, automotive engineering principles, and established diagnostic best practices. Key reference sources include:
- U.S. EPA — On-Board Diagnostics (OBD)Official EPA documentation on OBD-II standards and emissions monitoring requirements for passenger vehicles.
- ASE — Automotive Service ExcellenceIndustry certification body for automotive technicians; sets best-practice diagnostic and repair standards.
Informational purposes only. This guide is for educational reference and is not a substitute for diagnosis by a qualified technician. Repair costs, causes, and symptoms may vary by vehicle make, model, year, and condition. Always consult a licensed mechanic before performing major repairs.