P0273 — Cylinder 5 Injector Circuit Low

What does P0273 mean exactly?

P0273 means the control module detected an abnormally low voltage condition in the cylinder 5 injector circuit. It identifies the affected circuit, but it does not by itself prove that the injector is defective.

Can I keep driving with P0273?

Driving is best limited until the fault is repaired because an inactive cylinder 5 can cause poor fuel economy, catalyst damage, and continued roughness. Stop driving if the engine shakes severely, loses substantial power, or smells strongly of fuel.

Is the cylinder 5 injector always the bad part?

No. P0273 can also result from a shorted wire, damaged connector, poor terminal, or injector-control-driver failure. Voltage comparison and resistance testing are needed before replacing the injector.

Does clearing P0273 fix the problem?

Clearing P0273 only erases the stored code and does not correct the low-voltage condition. After repairs, clear the code and verify that it does not return during a road test and follow-up OBD scan.

When your check engine light comes on and a scan tool pulls code P0273, your engine control unit has identified a problem with the fuel injection system on cylinder 5 specifically. The technical definition reads "Cylinder 5 Injector Circuit Low," which tells you the powertrain computer is seeing an electrical fault that prevents the fuel injector for that cylinder from operating within its intended range. P0273 falls under the broader category of powertrain codes, meaning it affects the engine or transmission control systems rather than chassis, body, or network communications.

To understand why P0273 triggers, you need a basic picture of how fuel injection works. Each cylinder has its own injector that sprays precise amounts of fuel into the intake port or combustion chamber. The engine control module (ECM) or powertrain control module (PCM) energizes each injector with a specific voltage signal at precisely the right moment in the firing order. When P0273 sets, it means the voltage on cylinder 5's injector circuit stays abnormally low—essentially stuck near ground potential. This prevents the injector from firing at all, or causes it to behave erratically. The ECU doesn't flag this on a single bad reading; it waits for the condition to repeat under specific operating conditions before illuminating the warning light and logging the fault.

Locating cylinder 5 matters for repair planning. On inline engines, counting starts from the front—usually the belt end. On V-configuration engines, cylinder numbering varies by manufacturer, so consulting your vehicle's firing order diagram is essential before any work begins. Some cylinders sit easily accessible while others require removing the intake manifold or other components, which directly impacts labor time and your final bill. The freeze frame data stored alongside P0273 captures engine load, RPM, coolant temperature, and vehicle speed at the moment the fault occurred, giving you a roadmap of exactly what conditions to recreate during testing.

Common Symptoms of P0273

• Noticeable loss of engine power, especially under acceleration or load
• Rough idle that feels uneven or lumpy
• Hesitation or stumble when you push the accelerator
• Fuel consumption climbing noticeably compared to normal
• Extended cranking time when starting the engine
• Check Engine Light illuminated on the dashboard
• Raw fuel odor present, particularly in more severe cases

What Causes P0273?

• Loss of electrical supply voltage reaching the cylinder 5 injector
• The injector signal wire shorted to ground due to damaged or chafed insulation
• The cylinder 5 injector itself failed internally and pulling the circuit low
• Fuel contamination or the wrong fuel grade in the tank
• Vacuum leaks or intake manifold leaks disrupting the air-fuel mixture
• A faulty fuel pressure regulator unable to maintain proper rail pressure
• Multiple clogged or leaking injectors affecting cylinder operation
• A weak fuel pump or restricted fuel filter limiting delivery pressure

How to Diagnose P0273

1. Plug in an OBD2 scanner and confirm P0273 is stored in the ECU memory. Save all freeze frame data—this snapshot tells you engine load, RPM, temperature, and speed exactly when the fault first appeared.

2. Check for any related diagnostic trouble codes before focusing solely on P0273. Codes pointing to fuel pressure, mixture control, or other cylinders often reveal the root cause. Search manufacturer technical service bulletins using your VIN, as many fuel system issues have documented factory fixes or software updates available.

3. Perform a thorough visual inspection of the wiring harness and electrical connectors associated with cylinder 5's injector. Look for damaged insulation, exposed wires, corrosion at the connector pins, or loose connections that could interrupt the signal.

4. Test for supply voltage at the cylinder 5 injector connector first. Then measure resistance from the signal wire to ground—a reading near zero ohms definitively confirms a short to ground somewhere in the harness.

5. Measure fuel pressure at the rail with a gauge designed for the purpose. Compare your readings against factory specifications at idle and again while simulating load conditions.

6. Review short-term and long-term fuel trim values in the scanner's live data stream. Sustained positive or negative trims indicate whether the ECU is compensating for a rich or lean condition, helping narrow down whether the issue is electrical or fuel-delivery related.

7. Clear the code, complete a drive cycle that replicates the freeze frame conditions (same load, speed, and temperature), and verify P0273 does not return. If it comes back, the root cause remains unresolved.

Repair Options and Costs

Addressing P0273 means fixing whichever component in the fuel delivery or injection circuit has failed. The most cost-effective approach is starting with the cheapest and most frequently encountered causes before moving to expensive replacements:

• Fuel pump replacement: $400–$900
• Injector cleaning or replacement: $200–$800
• Fuel pressure regulator or sensor replacement: $150–$450
• Fuel filter replacement: $80–$200

Total Repair Cost for P0273

Your actual spend depends entirely on which part is faulty. At independent shop rates in the United States, typical scenarios break down as follows: fuel pump work runs $400–$900 including parts and labor, injector service costs $200–$800 depending on whether you clean existing injectors or buy new ones, pressure regulator replacement runs $150–$450, and fuel filter swaps are the least expensive at $80–$200. In most cases, the total bill for fixing P0273 falls somewhere between $80 and $900. An accurate electrical diagnosis before purchasing parts is the single best way to keep costs manageable—the most expensive component is rarely the culprit.

Can You Drive with P0273?

Drive with caution. When cylinder 5's injector isn't working properly, the engine runs on an uneven fuel delivery, which can cause stalling, hesitation, and poor throttle response. In severe cases, unburned fuel entering the exhaust stream can overheat and damage catalytic converters, turning a relatively simple fix into a major repair. Short trips to a repair facility are acceptable, but avoid extended highway driving or heavy traffic situations until the issue is properly diagnosed and repaired.

Related OBD2 Codes

• P0200: Injector Circuit Malfunction
• P0201: Injector Circuit Malfunction - Cylinder 1
• P0202: Injector Circuit Malfunction - Cylinder 2
• P0203: Injector Circuit Malfunction - Cylinder 3
• P0204: Injector Circuit Malfunction - Cylinder 4
• P0205: Injector Circuit Malfunction - Cylinder 5