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DTC codes / P02xx · Fuel and air metering (injector circuits) / P0273

P0273Cylinder 5 Injector Circuit Low

P0273 means the engine computer has detected an abnormally low voltage on the electrical circuit that operates the fuel injector for cylinder 5. The computer commands the injector to open, but the return voltage it monitors stays below the expected threshold, indicating a short to ground, a failing injector coil, or a wiring problem on that specific circuit.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or a noticeable misfire that feels like a shake or stumble
  • Loss of power and sluggish acceleration, especially under load
  • Slightly rough running when the engine is cold that may improve when warm
  • A faint fuel smell from the exhaust if the injector is stuck open or leaking
  • Poor fuel economy if the injector is not delivering fuel correctly

Common causes, most likely first

  1. Faulty cylinder 5 fuel injector with an internally shorted coil
  2. Chafed or grounded wire in the injector harness between the computer and the injector
  3. Corroded or loose electrical connector at the cylinder 5 injector
  4. Short to ground in the injector driver circuit inside the engine computer (less common)
  5. Aftermarket or damaged injector with incorrect resistance
  6. Moisture intrusion into the injector connector or harness causing a low-resistance path

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm the code is current and not history
  2. Inspect the cylinder 5 injector connector and harness for corrosion, chafing, or loose pins
  3. Measure the injector coil resistance with a multimeter and compare it to the manufacturer's specification
  4. Check the injector circuit for a short to ground by back-probing the computer connector with a multimeter
  5. Perform a wiggle test on the harness while watching live injector data or a noid light
  6. Swap the cylinder 5 injector with a known-good injector from another cylinder to see if the code moves
  7. If the circuit and injector test good, diagnose the engine computer driver circuit or replace the computer as a last resort

What a low injector circuit really means

  • A low circuit code does not automatically mean the injector is bad; a shorted section of harness rubbing against the engine block is just as common and much cheaper to fix.
  • Many technicians replace the injector only to find the code returns because the connector pins were spread or corroded, so always inspect the plug before condemning the part.
  • The engine computer may set P0273 even when the injector still fires; a partially shorted coil can draw excessive current without completely failing, causing a misfire that comes and goes.
  • A short to ground in the injector driver circuit can damage the computer if the fault is not found, so do not ignore the code or keep clearing it.
  • Related misfire codes such as P0305 or injector circuit codes for other cylinders often appear alongside P0273 and can point to a shared harness problem rather than a single injector.

Can I keep driving with P0273?

You can usually drive a short distance to a repair shop, but avoid heavy acceleration, towing, or long highway trips because a misfiring cylinder can overheat the catalytic converter and cause expensive damage. If the check engine light starts flashing, stop driving and have the vehicle towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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