P0273

Cylinder 5 Injector Circuit Low

P0273 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 5 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
P0273
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0273 means

P0273 is set when the ECM/PCM detects that the voltage on the fuel injector control circuit for cylinder 5 is below the manufacturer-specified minimum. The module monitors current and voltage through an internal transistor driver for each injector; when the return signal on cylinder 5's circuit falls too low — indicating an open circuit, excessive resistance, or a failed injector solenoid — it logs P0273 and illuminates the MIL.

Cylinder 5 is present in five-or-more-cylinder engines: five-cylinder units such as the Audi/VW 2.5 R5 TFSI and 2.5 TDI, Volvo five-cylinders, and older Fiat/Alfa 2.5 units; straight-six engines including BMW N52/N54/B58, Mercedes OM642 and M256, Cummins 5.9/6.7, and Land Rover TD6; and V8 and larger engines where cylinder 5 is typically the first cylinder on Bank 2. The physical location and access difficulty for injector 5 varies significantly between layouts, which should be factored into the repair estimate.

As with all injector-circuit-low codes, a dead or underperforming cylinder 5 will cause rough running and unburned fuel in the exhaust. Prompt attention is needed to prevent catalytic converter damage and to avoid worsening drivability.

Common causes

Most-frequently reported root causes when P0273 is logged.

  • 1
    Faulty cylinder 5 fuel injector with an open or shorted internal solenoid coil.
  • 2
    Broken, chafed, or corroded wiring in the injector control harness feeding cylinder 5.
  • 3
    Loose, corroded, or moisture-damaged electrical connector at the cylinder 5 injector.
  • 4
    Blown injector fuse or faulty injector relay affecting the cylinder 5 power supply.
  • 5
    High-resistance or open ground path in the cylinder 5 injector circuit.
  • 6
    Contaminated or clogged injector causing abnormal electrical loading on the ECM driver.
  • 7
    Failed ECM injector driver transistor for the cylinder 5 output channel.

Symptoms drivers notice

MIL illuminated, frequently accompanied by a cylinder 5 misfire code (P0305).
Rough idle and engine vibration, most noticeable at low rpm where the dead cylinder has the greatest relative effect.
Loss of power and hesitation or stumble when accelerating, particularly under load.
Reduced fuel economy as the ECM adjusts fuel trims to compensate for the underperforming cylinder.
Possible engine stalling at idle, especially on smaller five-cylinder engines where each cylinder contributes a larger proportion of total torque.
Elevated hydrocarbon emissions and possible smell of unburned fuel from the exhaust.

How to diagnose P0273

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, capture all DTCs and freeze-frame data, and confirm P0273 recurs after clearing.
  2. 2
    Visually inspect the wiring harness and connector at the cylinder 5 injector — check for corrosion, pushed-back pins, melted insulation, and heat damage.
  3. 3
    With ignition on and engine off, measure voltage at the injector power terminal; expect battery voltage (11.5–12.5 V) — low reading indicates a wiring, fuse, or relay fault.
  4. 4
    Measure injector coil resistance with a multimeter against the OEM spec; an open reading (OL/infinity) or significantly out-of-range value confirms a faulty injector.
  5. 5
    Swap the cylinder 5 injector with one from an adjacent cylinder and retest — if the code moves, replace the injector; if it stays at cylinder 5, focus on the wiring or ECM.
  6. 6
    Check for continuity and absence of shorts to ground or voltage in the full harness run between the ECM connector and the cylinder 5 injector plug.
  7. 7
    If wiring and injector test within spec, test the ECM driver channel with an oscilloscope before condemning the module.

Related powertrain codes

Frequently asked questions

Which vehicles are most likely to show P0273?

Any vehicle with five or more cylinders: Audi/VW five-cylinder engines (2.5 TDI, 2.5 TFSI), Volvo five-cylinders, BMW inline-six (N52, N54, B58), Mercedes inline-six (M256), Cummins 5.9/6.7 diesels, and most V8/V10 engines where cylinder 5 is the first cylinder on Bank 2. Four-cylinder engines do not have a cylinder 5 and will never set P0273.

Is P0273 an electrical fault or a mechanical one?

P0273 is specifically an electrical circuit fault — the ECM sees abnormally low voltage on the injector control circuit. Mechanical issues with the cylinder itself (compression, valves) would produce a contribution/balance fault (P0275) rather than P0273.

Can I drive with P0273 active?

Only for a very short distance if necessary. The misfiring cylinder 5 passes raw fuel into the exhaust, risking catalytic converter damage within a relatively short driving distance. Have the vehicle inspected as soon as possible.

How do I find cylinder 5 on a V8?

On most domestic V8s (GM, Ford, Chrysler) and many European V8s, cylinder 5 is the first cylinder on the passenger-side bank (Bank 2) when facing the engine from the front. Always verify with the manufacturer's cylinder numbering diagram for your specific engine, as conventions differ.

Disabling P0273 in software

RaceTune can permanently disable P0273 — 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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