P0270

Cylinder 4 Injector Circuit Low

P0270 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 4 Injector Circuit Low. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0270
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0270 means

P0270 is set when the Engine Control Module (ECM/PCM) detects that the voltage signal on the fuel injector control circuit for cylinder 4 has dropped below the manufacturer-specified threshold. The ECM drives each injector solenoid through an internal transistor (driver); when the return voltage or current is too low — typically caused by excessive resistance or an open in the circuit — the module logs this code and illuminates the MIL.

Cylinder 4 applies to any four-or-more-cylinder engine. In a four-cylinder engine this is the last cylinder; in larger engines the position depends on the firing order. Because one injector is effectively underperforming or disabled, the affected cylinder receives insufficient fuel, leading to a cylinder-4 misfire and the accompanying rough running, vibration, and power loss.

Left unresolved, the raw fuel that is not combusted in cylinder 4 can enter the exhaust stream and overheat the catalytic converter, potentially causing permanent catalyst damage in addition to the drivability issues already present.

Common causes

Most-frequently reported root causes when P0270 is logged.

  • 1
    Faulty cylinder 4 fuel injector with an internally open or shorted solenoid coil.
  • 2
    Broken, chafed, or corroded wiring in the injector control harness between the ECM and cylinder 4 injector.
  • 3
    Loose, corroded, or water-damaged electrical connector at the cylinder 4 injector.
  • 4
    Blown fuse or faulty injector relay supplying power to the injector bank.
  • 5
    Contaminated or clogged injector causing abnormal electrical load on the driver circuit.
  • 6
    Failed ECM injector driver transistor for cylinder 4 output.
  • 7
    High-resistance ground connection in the injector circuit ground path.

Symptoms drivers notice

MIL (check engine light) illuminated, often with a cylinder 4 misfire code (P0304) stored alongside.
Rough idle and noticeable engine vibration due to cylinder 4 not firing correctly.
Reduced engine power and hesitation or stumble under acceleration.
Increased fuel consumption as the ECM attempts fuel-trim corrections.
Possible engine stalling, especially at low rpm or when the engine is cold.
Elevated hydrocarbon emissions at the tailpipe from unburned fuel.

How to diagnose P0270

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all stored codes and freeze-frame data, then clear codes and road-test to confirm P0270 recurs.
  2. 2
    Visually inspect the wiring harness and connector at the cylinder 4 injector for corrosion, pushed-back pins, chafing, or heat damage.
  3. 3
    With the ignition on and engine off, check voltage at the injector connector power terminal — expect battery voltage (11.5–12.5 V); low voltage suggests a wiring or fuse fault.
  4. 4
    Measure injector coil resistance with a multimeter (reference the OEM spec, typically 11–16 Ω for port injectors or 0.3–2 Ω for GDI); readings outside spec indicate a faulty injector.
  5. 5
    Swap the cylinder 4 injector with a known-good injector from another cylinder and retest — if the fault follows the injector, replace it.
  6. 6
    If wiring and injector test good, inspect the ECM injector driver channel with an oscilloscope or injector-test function on a professional scan tool.
  7. 7
    Repair or replace any damaged wiring, connectors, or the injector before clearing codes and performing a final verification drive.

Related powertrain codes

Frequently asked questions

Can I drive with a P0270 code?

Short distances are possible but not recommended. The misfiring cylinder passes raw fuel into the exhaust, which can overheat and destroy the catalytic converter. Address the fault promptly.

Will cleaning the injector fix P0270?

If a partially clogged injector is causing abnormal electrical loading, professional ultrasonic cleaning may resolve it. However, an internally open or shorted coil requires injector replacement — cleaning will not fix an electrical fault.

Why does P0270 often appear with a P0304 misfire code?

They are closely related: a low-circuit fault means the injector is not delivering fuel correctly, so the cylinder misfires. Both codes point to the same root cause in cylinder 4.

Could the ECM itself be the problem?

ECM driver failure is possible but uncommon. Always rule out the injector, wiring, and connectors first, as those account for the vast majority of P0270 cases.

Disabling P0270 in software

RaceTune can permanently disable P0270 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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