P0261: Circuito Bajo del Inyector del Cilindro 1
El código de diagnóstico de falla (DTC) P0261 indica que el módulo de control del motor (ECM/PCM) ha detectado que el voltaje eléctrico en el circuito de control del inyector de combustible correspondiente al cilindro 1 ha descendido por debajo de los umbrales operativos calibrados, o que existe una derivación excesiva de corriente hacia masa. En sistemas diésel de riel común, el inyector es alimentado con alta tensión (80V a 200V) proveniente del convertidor elevador de voltaje (boost converter) de la ECU, y la etapa de control de lado bajo (low-side) es conmutada a masa mediante un transistor MOSFET de potencia de alta velocidad. El código P0261 se almacena cuando la línea de control de lado bajo se cortocircuita al chasis o tierra del vehículo, cuando la degradación del aislamiento en el embobinado interno comunica el actuador con la culata, o cuando la etapa de salida del ECM detecta una rampa de corriente anormalmente rápida.
🚗 Seguridad operativa, presupuesto estimado y verificación
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🚦 Seguridad de conducción y riesgo mecánico
Evaluación mecánica inmediata y necesidad de grúaCortocircuito a masa en circuito del inyector del cilindro 1 - Riesgo de fallo de etapa de potencia ECU
El circuito de control del inyector del cilindro 1 está en cortocircuito a masa. En sistemas common-rail, una derivación a masa del circuito de alta tensión dispara la protección por sobrecorriente de la ECU, corta la inyección del banco entero y fuerza el modo de emergencia.
PELIGROS MECÁNICOS SI CONTINÚA CONDUCIENDO:Un cortocircuito persistente puede quemar el banco de condensadores elevadores de tensión internos de la ECU del motor. - 02
💰 Presupuesto típico de taller
Niveles de costo esperados para repuestos y mano de obraMantenimiento menor / Filtro45 € - 95 €: Localización del punto de fricción del cableado y reparación con soldadura y funda termorretráctilLimpieza de sensor, cambio de filtro de combustible, revisión de fusibles o conectores.
Cambio de válvula / Sensor220 € - 520 €: Sustitución del inyector del cilindro 1 por bobina interna derivada al cuerpoSustitución de componente individual (válvula reguladora, unidad dosificadora o inyector reconstruido).
Reparación mayor / Bomba e inyectores750 € - 1800 €: Reparación de la etapa de potencia de la ECU o sustitución del mazo de cables del motorRevisión de bomba de alta presión, juego de inyectores nuevos o sustitución del conjunto DPF.
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🧰 Verificaciones visuales rápidas en garaje
Chequeo de 5 minutos sin herramientas antes de ir al taller11. Inspeccionar el cableado del inyector del cilindro 1 a lo largo del perfil de la tapa de balancines o soporte del rail en busca de rozaduras contra masa metálica.22. Desconectar el enchufe del inyector y medir la resistencia entre cada conductor y el borne negativo de batería (debe marcar circuito abierto / OL).33. Medir la resistencia entre los terminales del inyector y su cuerpo metálico exterior. Cualquier valor inferior a 500 kOhm confirma la derivación interna de la bobina. - 04
🛡️ Protección ante diagnósticos erróneos en taller
Preguntas técnicas exactas para evitar sustituciones de piezas innecesarias""Desconecte el inyector del cilindro 1 y compruebe si el DTC pasa de cortocircuito a masa a circuito abierto; esto discrimina si el fallo es del inyector o del cableado.""
""No reemplace la ECU sin realizar previamente una comprobación de aislamiento a 250 V con megóhmetro en el mazo de cables del motor.""
""Verifique que las cintas de masa entre la culata y el chasis estén firmes, limpias y con una resistencia inferior a 0.2 Ohm.""
Nota técnica: Haga estas preguntas técnicas a su mecánico antes de autorizar presupuestos caros:
Triaje de taller en 30 segundos
- Violent engine shaking, severe shudder, and continuous single-cylinder misfire under all operating conditions
- Significant loss of vehicle acceleration, sluggish throttle response, and inability to maintain highway cruising speeds
- Illuminated Check Engine Light (MIL) accompanied by flashing glow plug warning light and ESP/traction warning
- Cylinder 1 injector low-side control wire pinched, chafed, or shorted to vehicle chassis ground against the cylinder head or valve cover
- Internal dielectric breakdown or winding short to ground inside the Cylinder 1 fuel injector electromagnetic solenoid or piezo stack
- Corroded, wet, or water-contaminated terminal pins inside the Cylinder 1 injector connector creating a conductive path to ground
Connect scan tool live telemetry: compare Target Fuel Rail Pressure vs Actual Rail Pressure and log metering valve command PWM duty cycle during idle and road load.
Expensive Diagnostic Pitfall & Technical Reality
P0261 means Cylinder 1 common rail fuel injector has failed internally and must be replaced immediately with full coding ($450 - $900).
P0261 indicates that the ECM's injector driver circuit detected that the Cylinder 1 high-side or low-side signal wire is shorted to ground or has an abnormally low voltage during actuation. In over 80% of verified cases, the injector solenoid coil itself is in perfect working order. The failure is driven by the engine wiring harness chafing through its protective sleeve and shorting to the cylinder head aluminum casing, engine oil contamination inside the valve cover harness connector, or terminal pins in the ECM plug being pushed back.
Unnecessarily spending $650 on a new injector vs finding the harness rub-through with a multimeter ($0) and insulating with $5 heatshrink, saving over $600.
Motores y plataformas de inyección más afectados
Este código de error afecta principalmente a las siguientes plataformas diésel common rail. Consulte su familia de motores para ver fallos típicos y referencias de piezas:
BMW 2.0d / 3.0d (N47 / N57 / M57TU2)
Bosch CRI2.5 / CRI3.0 Common RailFallo típico de fábrica: Injector balance drift beyond +/- 4.0 mg/stroke, glow plug control unit (BERU) power lead failure, DPF backpressure accumulation.
13537805428, 0445116024, 12217801201Ford / PSA 1.6 TDCi / HDi (DV6ATED4 / DLD-416)
Bosch CRI2-16 Common Rail SystemFallo típico de fábrica: Injector copper washer blow-by (black death), injector cylinder circuit fretting corrosion, DPF pressure pipes heat cracking.
0445110239, 1980J7, 1618LPVolkswagen / Audi 2.0 TDI (EA189 / CFFB / CFGB)
Bosch EDC17 Common Rail SystemFallo típico de fábrica: Piezo stack degradation, injector harness terminal fretting, DPF differential pressure sensor silicone tube split.
03L130277, 0445110369, 076906051AMercedes-Benz 2.1 CDI (OM651 / OM646)
Delphi CRD2 / Bosch Common Rail InjectionFallo típico de fábrica: Delphi piezo to solenoid conversion wiring harness chafing, differential pressure sensor internal diaphragm drift.
A6510704987, A6510700587, A0061539528P0201-P0204 Injector Circuit Diagnosis Guide
Workshop troubleshooting guide for OBD-II codes P0201 to P0204 (Cylinder 1-4 Injector Circuit Malfunction). Resistance test specs, harness checks, and ECU driver stage.
Circuito de control y lógica del actuador
1. Dynamic In-Demand Fuel Metering
The Cylinder 1 common rail fuel injector circuit consists of a high-side supply line and a low-side control line. When firing, the ECM high-side driver gates an 80V-200V capacitor pulse, while the low-side driver pulls the return wire to ground, completing the circuit. The low-side circuit incorporates an internal diagnostic sense resistor. When the injector de-energizes, the collapsing magnetic field generates an inductive flyback voltage spike that is captured and evaluated by the ECM. If the low-side wire is pinched against the engine block, voltage remains pinned to 0V (ground), triggering P0261.
2. Closed-Loop PID Deviation Monitoring
The ECM executes circuit diagnostics both continuously during engine running and statically at Key-ON. If the voltage on the Cylinder 1 low-side driver line remains below 1.5 V during the un-energized rest state (where pull-up voltage is expected), or if the current-sense circuit detects immediate over-current upon initial gating, P0261 is set. To prevent the short circuit from draining the ECM's shared boost capacitor (which would shut down the entire cylinder bank), the ECM de-energizes the high-side supply to Cylinder 1.
3. Diagnostic Trap: Normally Open (NO) vs Normally Closed (NC) Valves
Short-to-Ground vs Internal Actuator Short Diagnostic Rule: A P0261 'Circuit Low' can be caused by the wiring harness rubbing against the metallic valve cover, OR by internal dielectric breakdown inside the injector solenoid/piezo stack. Unplug the Cylinder 1 injector: if P0261 immediately flips to P0201 (Open Circuit), the wiring harness and ECM driver are 100% HEALTHY-the injector itself is shorted internally to ground! If P0261 remains with the injector completely unplugged, the wiring harness wire is pinched to ground.
Valores físicos eléctricos e hidráulicos
Protocolo de Diagnóstico de Taller Paso a Paso
Unplug Diagnostic Flip Test (Isolating Harness vs Injector)
Turn the ignition Key-ON with the engine stopped. Clear stored trouble codes. Unplug the electrical connector from the Cylinder 1 fuel injector while monitoring live scan tool codes. If code P0261 immediately clears and transforms into P0201 (Cylinder 1 Circuit Open), the vehicle wiring harness and ECM driver are 100% HEALTHY-the injector itself is internally shorted to ground! If P0261 persists with the injector completely disconnected, the wiring harness is shorted to ground.
High-Voltage Megohmmeter (Insulation Resistance) Test
With the Cylinder 1 injector removed or disconnected, use an automotive insulation tester (Megohmmeter) set to 250V or 500V test voltage. Connect one lead to the metal injector body and the other to each terminal pin in turn. Insulation resistance must be greater than 10 MΩ (typically >100 MΩ). Any reading below 10 MΩ confirms internal ceramic or enamel insulation breakdown arcing to ground under load.
Precision Four-Wire Low-Resistance Coil Measurement
Using a milliohm meter or digital multimeter with lead-zeroing on the lowest ohms scale, measure resistance across the two pins of the Cylinder 1 injector: normal resistance for solenoid injectors is 0.20 Ω to 0.45 Ω @ 20°C; for piezo injectors, 180 kΩ to 220 kΩ. A reading of 0.0 Ω (dead short) indicates fused coil windings.
Harness Short-to-Ground Ohms Continuity Audit
If the unplug test indicated a harness fault, turn Key-OFF and disconnect the ECM main harness plug. Using a multimeter on ohms scale, measure resistance between the Cylinder 1 low-side control wire pin and vehicle chassis ground. Resistance must be infinite (OL). If resistance is low (<100 Ω), visually trace the harness over the valve cover, bellhousing, and intake manifold to locate rubbed-through insulation.
Connector Water Ingress & Pin Inspection
Inspect the Cylinder 1 connector seal and terminal cavities. Engine oil pooling from leaking valve cover gaskets or coolant from a leaking coolant flange can seep into the connector, creating an electrolytic short circuit between the high-voltage pin and engine ground. Clean thoroughly with electronic contact cleaner and inspect terminal pin retention.
Oscilloscope Ground-Side Switching Waveform Verification
Back-probe the low-side control wire with an oscilloscope. Crank the engine: verify that the low-side driver pulls the signal cleanly to ground during firing and releases cleanly with a sharp flyback voltage clamp. If the trace remains permanently flat at ground (0V), the internal ECM low-side driver MOSFET has failed shorted.
Reparación de hardware y lista de piezas BOM
Cylinder 1 Common Rail Injector Drive & Wiring Subsystem
0 445 110 369 / 0 445 116 059
High-speed electro-hydraulic fuel injector with calibrated pilot/main injection metering
1 928 498 056 / Tyco Junior Timer 2-Way
Provides positive terminal spring tension to withstand 150V injection pulse vibrations
OEM Heat-Shielded Injector Sub-Loom
Protects injector command lines from constant 120°C hot engine oil splash
Calculadora interactiva de tolerancias Common Rail
Componentes de inyección asociados
Las siguientes bombas de combustible e inyectores common rail originales están verificados para motores con el código P0261. Verifique las presiones de trabajo antes del reemplazo:
0445110239BOSCH
0445110239 Injector: PSA 1.6 HDi Ford 1.6 TDCi Specs
View Technical Specs & Fitment →0445110369BOSCH
0445110369 Injector: VW 2.0 TDI EA189 CFFB CFHC Specs
View Technical Specs & Fitment →0445116024BOSCH
BOSCH 0445116024 Common Rail Piezo Injector for BMW N47 2.0d & N57 3.0d
View Technical Specs & Fitment →095000-5880Denso
095000-5880 Denso Toyota 2KD-FTV Injector: 23670-30050 Data
View Technical Specs & Fitment →28337917Delphi
28337917 Delphi Bobcat D24 Injector: 7030364 Specs & Data
View Technical Specs & Fitment →095000-8340Denso
095000-8340 Denso Mitsubishi 4D56 HP Injector: 1465A367 Data
View Technical Specs & Fitment →Reinicio de adaptación de bomba y ciclo de rodaje
Following replacement of the Cylinder 1 fuel injector or repair of the shorted wiring harness, execute the calibration routine:
1. Enter the new 6-to-30 digit alphanumeric calibration code (IMA / QR code) stamped on the top of the new Cylinder 1 injector into the ECM via scan tool.
2. Clear all stored trouble codes and ensure battery voltage is fully charged (>12.5 V).
3. Access scan tool 'Engine Control Module' -> 'Special Functions' -> select 'Reset Injector Driver Stage Fault Memory'.
4. Start the engine and let it idle at full operating temperature (coolant >80°C) for 5 minutes without touching the accelerator.
5. The ECM will perform smooth-running control (SRC) zero-fuel calibration cycles to re-balance cylinder torque.
6. Conduct a 15-minute road test through all gear ranges, verifying smooth idle, instant throttle response, and zero pending DTCs.
Diagnóstico diferencial y códigos relacionados
Injector Circuit/Open - Cylinder 1
Companion open-circuit fault on Cylinder 1; unplugging a shorted injector will transform P0261 into P0201, confirming the injector is bad.
Cylinder 1 Injector Circuit High
Opposite electrical circuit failure: occurs when the injector control wire is shorted to 12V battery power or 80V boost supply.
Cylinder 1 Misfire Detected
Direct mechanical consequence: because the ECM disables the shorted Cylinder 1 injector, Cylinder 1 fails to fire, setting misfire code P0301.
Casos reales de taller
2015 Ford Focus 2.0 TDCi (DW10C)(168,000 km)
Preguntas técnicas frecuentes
¿Qué significa el código de fallo P0261?
El código de diagnóstico de falla (DTC) P0261 indica que el módulo de control del motor (ECM/PCM) ha detectado que el voltaje eléctrico en el circuito de control del inyector de combustible correspondiente al cilindro 1 ha descendido por debajo de los umbrales operativos calibrados, o que existe una derivación excesiva de corriente hacia masa. En sistemas diésel de riel común, el inyector es alimentado con alta tensión (80V a 200V) proveniente del convertidor elevador de voltaje (boost converter) de la ECU, y la etapa de control de lado bajo (low-side) es conmutada a masa mediante un transistor MOSFET de potencia de alta velocidad. El código P0261 se almacena cuando la línea de control de lado bajo se cortocircuita al chasis o tierra del vehículo, cuando la degradación del aislamiento en el embobinado interno comunica el actuador con la culata, o cuando la etapa de salida del ECM detecta una rampa de corriente anormalmente rápida.
¿Cuáles son los síntomas más comunes de P0261?
Violent engine shaking, severe shudder, and continuous single-cylinder misfire under all operating conditions, Significant loss of vehicle acceleration, sluggish throttle response, and inability to maintain highway cruising speeds, Illuminated Check Engine Light (MIL) accompanied by flashing glow plug warning light and ESP/traction warning, Heavy puffing of white or grey unburned diesel smoke from exhaust pipe during cold start and acceleration, Strong, pungent odor of raw diesel fuel surrounding the vehicle exhaust and engine bay, Diagnostic scan tool live data shows Cylinder 1 contribution balance pegged at maximum positive fuel trim (+4.5 to +6.0 mg/stroke).
¿Qué causa P0261 en un motor diésel?
Cylinder 1 injector low-side control wire pinched, chafed, or shorted to vehicle chassis ground against the cylinder head or valve cover; Internal dielectric breakdown or winding short to ground inside the Cylinder 1 fuel injector electromagnetic solenoid or piezo stack; Corroded, wet, or water-contaminated terminal pins inside the Cylinder 1 injector connector creating a conductive path to ground; Damaged or shorted internal low-side MOSFET power transistor inside the Engine Control Module (ECM); Engine wiring harness crushed or pinched under an engine bracket, alternator mount, or intake manifold flange during prior service; Insulation melting caused by wiring harness contact with the hot exhaust gas recirculation (EGR) pipe or turbocharger heat shield.
¿Es seguro conducir con el código P0261 activo?
🟡 Precaución: Modo emergencia activo / Acudir a taller
¿Cuánto cuesta reparar el código de avería P0261?
Los costes habituales de reparación para P0261 dependen de la causa raíz identificada en el diagnóstico: Nivel 1 (Mantenimiento menor / DIY): 45 € - 95 €: Localización del punto de fricción del cableado y reparación con soldadura y funda termorretráctil (Limpieza de sensor, cambio de filtro de combustible, revisión de fusibles o conectores.); Nivel 2 (Sustitución de componente): 220 € - 520 €: Sustitución del inyector del cilindro 1 por bobina interna derivada al cuerpo (Sustitución de componente individual (válvula reguladora, unidad dosificadora o inyector reconstruido).); Nivel 3 (Subconjunto mayor): 750 € - 1800 €: Reparación de la etapa de potencia de la ECU o sustitución del mazo de cables del motor (Revisión de bomba de alta presión, juego de inyectores nuevos o sustitución del conjunto DPF.). Tarifas de referencia de talleres. Más del 70% de las incidencias se resuelven en Nivel 1 o 2 sin sustituir subconjuntos completos.
What is the difference between code P0201 and code P0261?
P0201 is an OPEN circuit fault: current cannot flow because a wire is broken, a terminal pin is loose, or an internal coil winding has snapped. P0261 is a SHORT TO GROUND (Circuit Low) fault: current is escaping directly to the engine metal body before completing its normal path, either because the harness wire is pinched against metal or because the internal insulation inside the injector has broken down.
How does unplugging the injector prove whether the wiring or the injector is broken?
This is the fastest test in common rail diagnostics. If you unplug the injector and the code changes from P0261 (Circuit Low) to P0201 (Circuit Open), you have proven 100% that the wiring harness is NOT shorted to ground (because if the harness were shorted, unplugging the injector wouldn't change anything; the wire would still be touching ground). Therefore, the short was inside the injector itself, and replacing the injector will cure the car.
Can water in the engine bay cause trouble code P0261?
Yes, very frequently. If someone pressure-washes the engine bay or if water leaks past the scuttle panel drain onto the top of the engine, moisture can enter the injector harness connector. Because common rail injectors operate under high voltage (80V-200V), water acts as an electrical conductor, creating a conductive bridge between the terminal pin and the grounded cylinder head, triggering P0261.