What it means
Cylinder 4 Injector Circuit Low: the signal voltage is below the expected range. This affects fueling of the associated cylinders.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module switches and monitors the fuel injector circuit for cylinder 4 to deliver fuel at the commanded times. P0270 indicates the circuit signal is lower than expected, which can disrupt cylinder 4 fueling; it does not by itself prove that the injector is clogged.
Common causes
Most likely first.
- Injector winding failed open
- Wiring or connector fault
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Rough idle or misfire
- Reduced power
- Increased fuel consumption
How to diagnose it
- Record freeze-frame data and check misfire counts and cylinder-specific live data to see whether cylinder 4 is affected when the fault occurs.
- With the ignition off, inspect the cylinder 4 injector connector and nearby harness for loose pins, corrosion, damage, or chafing.
- Check the injector circuit for a short to ground, open, or excessive resistance using the vehicle wiring diagram and manufacturer's test procedure.
- Test the cylinder 4 injector winding and compare results with the manufacturer's specification.
- If wiring and injector tests pass, check the control module's injector driver and its connections before considering module replacement.
Common fixes
- Clean and secure the cylinder 4 injector connector or repair corroded terminals.
- Repair an open, grounded, or damaged section of cylinder 4 injector wiring.
- Replace the cylinder 4 injector if its winding fails the manufacturer's test.
- Repair the control module driver only after the injector and circuit have tested correctly.
Can I keep driving?
If the engine runs roughly or misfires, avoid hard acceleration and long trips; unburned fuel can damage the catalytic converter. Stop driving if the misfire is severe, the engine shakes heavily, or power drops enough to make driving unsafe.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.