What it means
The control module detects a low condition in the cylinder 11 injector circuit. This indicates an electrical circuit fault and does not by itself establish an injector flow problem.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The injector circuit supplies the electrical command for cylinder 11's fuel injector. P0291 sets when the control module detects a circuit voltage that is too low; this indicates an electrical fault and does not by itself show that the injector is clogged.
Common causes
Most likely first.
- Wiring shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine light
- Rough idle or misfire
- Reduced power
- Increased fuel consumption
How to diagnose it
- Use a scan tool to review freeze-frame data and check for cylinder 11 misfire or injector-circuit codes recorded at the same time.
- Inspect the cylinder 11 injector connector and harness for chafing, corrosion, moisture, or terminals pushed back in the connector.
- With the circuit active, gently move the cylinder 11 harness while monitoring the circuit reading to check for an intermittent fault.
- Test the cylinder 11 injector control wire for a short to ground and check terminal contact using the manufacturer's procedure.
- If the harness checks out, test the injector and module driver circuit against the manufacturer's specification.
Common fixes
- Repair cylinder 11 injector wiring that is shorted to ground or chafed.
- Clean or replace corroded cylinder 11 connector terminals and damaged seals.
- Restore a pushed-back or loose connector terminal.
- Replace the cylinder 11 injector or repair the driver circuit only if testing identifies it as faulty.
Can I keep driving?
A cylinder 11 injector circuit fault can cause a misfire, poor running, and increased fuel use. Avoid hard driving, and stop if the engine runs severely rough or the warning light flashes because continued misfiring can damage the catalyst.
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.