Toyota Yaris P0204: Injector Circuit Malfunction - Cylinder 4 diagnosis
Code verification standard
P0204 is published with SAE J2012 / ISO 15031-6 code structure plus Toyota Yaris diagnostic context.
This page covers meaning, symptoms, first checks, live data, misdiagnosis risk, and repair verification.
What does this mean?
Code P0204 indicates that the Powertrain Control Module (PCM) has detected an electrical malfunction within the fuel injector circuit for cylinder #4. This means the PCM is not seeing the expected resistance or voltage drop across the injector circuit during its operation. This could be due to an open circuit, a short to ground, a short to voltage, or excessively high/low resistance within the injector coil itself or its wiring. Symptoms often include a noticeable engine misfire, rough idle, reduced engine power, increased fuel consumption, and the illumination of the Check Engine Light.
How serious is this code?
Driving with a P0204 code is generally not recommended for extended periods. A malfunctioning injector circuit will cause cylinder #4 to misfire, leading to significant engine performance issues such as rough running, reduced power, and poor fuel economy. Continued driving can also lead to unburnt fuel entering the exhaust system, potentially causing severe and costly damage to the catalytic converter. It's best to diagnose and repair this issue promptly.
Diagnostic system: General powertrain circuit
On a Toyota Yaris, the P0204 code should be diagnosed as part of the general powertrain circuit group. Related codes and live data from this same system can change the repair priority, so avoid replacing parts from the code name alone.
Most Common Causes for Toyota Yaris
- Clogged or faulty fuel injector
- Damaged, chafed, or broken wiring harness
- Corroded or loose electrical connector
- Internal PCM/ECM failure
- Faulty fuel pressure regulator
Symptoms to Watch For
- Check Engine Light is illuminated
- Engine misfiring or shaking sensation
- Rough or unstable idle
- Significant loss of engine power
- Poor acceleration or sluggish response
Before replacing parts, check these first
- Record freeze-frame data and related codes before clearing the fault.
- Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system.
- Use live data or a multimeter to confirm the failed circuit before replacing parts.
- Check for blown fuses, weak battery voltage, and damaged connectors before buying major parts.
Live data to compare
- Freeze-frame conditions
- Related codes
- Circuit voltage and continuity
How to Diagnose
Common Mistakes
Treating the code description as a parts list instead of verifying the circuit, operating conditions, and related codes. Always confirm the fault with freeze-frame data, live data, visual inspection, and circuit checks before spending money on parts.
Repair verification
After the repair, clear P0204, complete a drive cycle, and confirm the monitor runs without the code returning. Save the before/after scan report if the vehicle needs emissions inspection.
Frequently Asked Questions
Can I drive with the P0204 code?
If the check engine light is solid, you can usually drive to a safe location or mechanic. If the light is flashing, pull over immediately to prevent catastrophic engine or catalytic converter damage.
Will the P0204 code clear itself?
Once the underlying problem is fixed, the engine computer will run its self-checks. If it passes over several drive cycles, the light will turn off automatically. You can also clear it immediately using an OBD2 scanner.
Will this code fail an emissions test?
Yes. If the Check Engine Light is on due to the P0204 code, your Toyota will automatically fail an OBD2 plug-in emissions or smog test.
What should I check first for P0204?
Record freeze-frame data and related codes before clearing the fault. Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system. Use live data or a multimeter to confirm the failed circuit before replacing parts.
Join the Discussion
Repair Estimate
Fuse, connector, wiring, cleaning, or basic inspection
Major component replacement after live data and circuit tests confirm failure
Costs vary widely; start with visual inspection and circuit confirmation to avoid unnecessary parts.
DIY Difficulty
Can usually be performed at home with basic hand tools.