P0291
UniversalCylinder 11 Injector Circuit Low
Medium SeverityThis code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the electrical circuit for the fuel injector of cylinder 11. This typically means the injector is not receiving the correct electrical signal to operate properly, leading to potential engine misfires and performance issues.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on electrical components of your vehicle. Ensure the engine is cool to the touch before attempting any repairs, especially around hot engine parts or the fuel system. Use appropriate eye protection and gloves, and be cautious when handling fuel to prevent leaks or fire hazards.
Common Symptoms
- Check Engine Light illumination
- Engine misfire
- Rough idling
- Poor acceleration
- Reduced fuel economy
- Engine hesitation
Common Causes
- Faulty fuel injector for cylinder 11
- Wiring harness issues (open, short, or corrosion) affecting cylinder 11 injector circuit
- Corroded or loose electrical connector at the injector
- Faulty Powertrain Control Module (PCM) driver for the injector
- Resistance in the injector circuit
Frequently reported on: All Makes
Diagnostic Steps
- Visually inspect the wiring harness and connector for cylinder 11 fuel injector for any signs of damage, corrosion, or loose connections.
- Using a multimeter, check the resistance of the cylinder 11 fuel injector. Compare it to specifications or a known good injector.
- With the key on and engine off, check for proper voltage at the injector connector. Then, check for a pulsing ground signal from the PCM during engine cranking.
- If accessible, swap the cylinder 11 fuel injector with a known good injector from another cylinder to see if the code follows the injector.
- If the injector tests faulty or the code follows the injector, replace the fuel injector for cylinder 11. Clear the code and retest.
👨🔧 When to Call a Professional
If you have performed basic diagnostics and confirmed the circuit issue is not a simple wiring problem, or if you are not comfortable testing fuel system components and PCM signals, it is highly recommended to seek professional diagnostic help to accurately pinpoint and repair the fault.
Commonly Asked Questions
What does 'Cylinder 11' refer to in the P0291 code?
It indicates that the detected low circuit issue is specifically with the fuel injector circuit connected to the eleventh cylinder in your engine's firing order or numbering scheme.
Can I continue driving my car with a P0291 code?
While it might be possible to drive, it's not recommended. A faulty injector can cause misfires, reduced engine performance, increased emissions, and potentially lead to further engine damage if left unaddressed.
How can I test the fuel injector circuit for low voltage?
You'll need a multimeter to check for proper voltage supply to the injector and to test for continuity and resistance within the injector's circuit and the injector itself. You can also check for a pulsing ground signal from the PCM.
Is a P0291 code always caused by a bad fuel injector?
Not always. While a bad injector is a common cause, the code could also point to issues with the wiring harness, a corroded connector, or even a fault within the engine control module (PCM) that controls the injector.
What's the difference between 'injector circuit low' and 'injector circuit high' codes?
'Circuit low' typically means there's insufficient voltage or a short to ground. 'Circuit high' usually indicates excessive voltage or an open circuit. Both refer to an electrical issue within the injector's circuit.