P0273
Cylinder 5 Injector A Circuit Low.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 73
- FaultThe specific fault in that area
What it means
P0273 means the engine control unit has detected a low voltage or low signal state in the control circuit for the cylinder 5 injector (injector A). The unit monitors the injector driver circuit, and it set the code because the voltage or current did not match what it expected. This usually points to a short to ground or a fault in the injector winding or its wiring. The exact injector type and circuit layout depend on the engine, so check the model-specific wiring information.
Symptoms
- Engine management warning light on
- Rough running or misfire on cylinder 5
- Hesitation or loss of power under load
- Poor fuel economy
- Hard starting or uneven idle
- Fuel smell or black smoke if the injector is leaking or stuck open
Possible causes
- Faulty cylinder 5 injector with internal winding short or incorrect resistancelikely
- Injector wiring chafed or shorted to ground between the injector and the control unitlikely
- Corroded, damaged or loose injector connector or harness connector pinslikely
- Low or unstable supply voltage to the injector circuit (blown fuse, relay fault, poor power feed or earth)possible
- Moisture or contamination in the connector or harness causing a leakage path to groundpossible
- Fault in the injector driver stage inside the control unitrare
- Previous repair damage or incorrect harness routing near cylinder 5rare
How to diagnose
- Read all stored and pending codes and note freeze frame data (engine load, temperature, rpm, battery voltage) to see when the fault occurred.
- Check for related misfire codes, especially cylinder 5, and any other injector or supply voltage codes.
- Visually inspect the cylinder 5 injector connector, harness routing and nearby wiring for chafing, heat damage, corrosion, water ingress and loose pins.
- Check the relevant fuses, relays and the battery and charging voltage, as low supply voltage can affect injector circuit readings.
- With the connector disconnected, measure the injector winding resistance and compare it with the manufacturer specification for that engine.
- Test the wiring from the injector connector to the control unit for short to ground, short to voltage and continuity, following the wiring diagram.
- Check the injector supply and control signal at the connector while cranking or running, using a suitable meter or oscilloscope.
- Where the design allows, swap the injector or its connector with another cylinder to see whether the fault follows, then clear the code and retest.
How to fix
- Replace the cylinder 5 injector if its resistance or operation is out of specification, following the correct procedure for that engine.
- Repair or replace damaged wiring and insulation where the circuit is shorted to ground.
- Clean, repair or replace corroded or damaged connectors and terminals, and ensure the connector locks fully.
- Restore correct power and earth supply by repairing fuses, relays, or poor connections found in the circuit.
- Diagnose and, if confirmed faulty, repair or replace the control unit, then carry out any required coding or setup for that model.
Can I keep driving?
The car can usually be driven short distances to get it checked, but get it fixed soon. Avoid heavy load and stop driving if it misfires badly, flashes the warning light, smells of fuel or runs very rough, as unburnt fuel can damage the catalytic converter and engine.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.