Cylinder 11 Injector Circuit Low
P0291 indicates that the fuel injector circuit for cylinder 11 is operating at lower voltage or resistance than expected. This causes incomplete fuel atomization, resulting in a lean fuel mixture in that cylinder and triggering the check engine light. The PCM compensates by enriching all cylinders, degrading fuel economy and engine performance.
What You Might Notice
- Check engine light illuminated
- Rough idle or uneven running
- Loss of engine power
- Significant decrease in fuel economy
- Engine hesitation during acceleration
Most Common Causes
- 1
Dirty or clogged fuel injector
Carbon buildup on the injector tip reduces spray pattern and fuel delivery to cylinder 11. This is the most common cause and can often be resolved with fuel system cleaning.
- 2
Faulty fuel injector
The injector coil is failing, preventing proper opening and closing. A defective injector must be replaced to restore proper fuel delivery.
- 3
Wiring or connector issues
Corroded, loose, or damaged wiring to the cylinder 11 injector reduces voltage delivery. Check all connections and harnesses for corrosion or poor contact.
- 4
PCM or fuel injector driver failure
The engine control module's injector driver circuit may be failing, preventing proper voltage signal to the fuel injector for cylinder 11.
How to Diagnose It
- 1
Check Dirty or clogged fuel injector — Carbon buildup on the injector tip reduces spray pattern and fuel delivery to cylinder 11. This is the most common cause and can often be resolved with fuel system cleaning.
- 2
Check Faulty fuel injector — The injector coil is failing, preventing proper opening and closing. A defective injector must be replaced to restore proper fuel delivery.
- 3
Check Wiring or connector issues — Corroded, loose, or damaged wiring to the cylinder 11 injector reduces voltage delivery. Check all connections and harnesses for corrosion or poor contact.
- 4
Check PCM or fuel injector driver failure — The engine control module's injector driver circuit may be failing, preventing proper voltage signal to the fuel injector for cylinder 11.
How to Fix It
- 1
Clean fuel injectors
Use a professional fuel system cleaner or take the vehicle to a shop for fuel injector cleaning service. This often resolves the code without requiring part replacement.
- 2
Replace fuel injector
Remove and replace the faulty fuel injector for cylinder 11 if cleaning does not resolve the code. Ensure the new injector matches OEM specifications.
- 3
Inspect and repair wiring
Check the injector harness and connector for corrosion, damage, or loose connections. Clean contacts with electrical cleaner and reconnect firmly, or replace damaged wiring.
- 4
Test and replace PCM if needed
If injector and wiring are good, the PCM injector driver circuit may be failing. Have the module tested by a specialist or replaced if diagnosis confirms PCM failure.
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