P0291 code definition
When your vehicle’s PCM registers the P0291 code, it means that a voltage reading came from the fuel injector circuit – for cylinder number 11’s fuel injector – that doesn’t conform to the predetermined value referenced by the manufacturer.
What the P0291 code means
Inadvertent resistance can lead to voltage variations. If they go above 10% of the amount of voltage referenced by the manufacturer, a P0291 code will be stored and the Check Engine light will generally come on. This code specifically references the fuel injector for cylinder number 11.
During normal conditions, the PCM switches the fuel injectors in your vehicle on and off within the fuel injection system.
What causes the P0291 code?
Oddly enough, the number one cause for this code being stored is actually squirrels. These little critters and other wildlife often find a way up into your hood because they recognize that your engine is warm for a long time after it’s parked. Not content to simply rest and be warm, though, these animals may decide to chew through important wires that leave you with fuel injectors unable to operate as they should.
There are a few other reasons you should know about too:
- A defective fuel injector
- Loose electrical wiring
- Corrosion on the electrical wiring
- Damaged connector faces
Sometimes, the fuel injector in your vehicle’s PCM may actually be responsible, but this is incredibly rare.
What are the symptoms of the P0291 code?
When a fuel injector isn’t able to function correctly, your ride is going to suffer. This means that you should notice early on when the problem occurs. Your vehicle may all of a sudden have a really tough time accelerating. The [engine could actually misfire) because of just one fuel injector’s problem. Even when you’re sitting at idle, you might find that your vehicle – or at least the ignition – vibrates intermittently.
How does a mechanic diagnose the P0291 code?
First, your mechanic is going to use an OBDII scanner to get a reading on the codes your PCM has stored. For a P0279 issue, they’ll most likely also use an ohmmeter, noid lamp and the vehicle’s user’s manual to figure out how bad the problem is.
Once they confirm there’s an issue, your mechanic will most likely examine all of the associated wires and connectors. If necessary, they may go on to examine your fuses too. All the while, the system should be reset to see if the code comes back or is permanently cleared.
Common mistakes when diagnosing the P0291 code
It’s extremely important that all relevant electrical components get checked before moving onto other possible repairs. It’s usually just a matter of replacing one or two before P0291 clears for good. Unfortunately, if your mechanic doesn’t do this, they may end up blaming the problem on your PCM, which would be a huge, unnecessarily costly mistake.
How serious is the P0291 code?
While this isn’t the type of problem that will necessarily increase your likelihood of getting into an accident, a P0291 code does mean your vehicle is operating at subpar levels. Aside from how frustrating this can be, it might also mean you end up spending a lot more at the pump. Also, if you don’t fix the fuel injector, the problem could have a damaging ripple effect.
What repairs can fix the P0291 code?
Your mechanic will do some combination of the following to get you back on the road:
- Replace the bad injector
- Clean out the fuel injector
- Replace or repair the fuel injector’s electrical connector
That last step is probably going to be all it takes. Electrical connectors can become corroded for all sorts of reasons or get loose and keep working correctly.
Additional comments for consideration regarding the P0291 code
Even if you don’t notice any serious ramifications from this code, get it fixed right away. As we mentioned earlier, fuel injection issues can quickly become much worse.
Need help with a P0291 code?
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