P0261
Cylinder 1 Injector Circuit Low
The appearance of the standard OBD2 trouble fault code P0261 is an indicator that your vehicle ECU triggered a threshold alert for "Cylinder 1 Injector Circuit Low". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Your vehicle's computer logged P0261 after detecting a malfunction in the cylinder 1 injector circuit low system. The most common signs are engine misfire, reduced power, check engine light on. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Engine misfire, reduced power, check engine light on
Common Causes
- Defective Cylinder 1 fuel injector
- Short to ground in injector wiring
- Poor electrical connection at the injector
- Failed PCM
How to Fix
- 1 Test and replace Cylinder 1 injector
- 2 Trace and repair shorted wiring
- 3 Clean and secure connector
- 4 Test PCM injector drivers
Technical Explanation
P0261 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
Driving with an active P0261 fault risks accelerating damage to defective cylinder 1 fuel injector and related components. The longer the fault persists, the more expensive the eventual repair becomes — what starts as a sensor or solenoid issue can escalate to major mechanical failure.
Mechanic's Pro Tip
Before replacing any component on P0261, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Injector replacement: $150 - $400