Skip the auto shop - Our mechanics make house calls

P0285 OBD-II Trouble Code: Cylinder 9 Injector Circuit Low

check engine light

P0285 code definition

The P0285 code is logged when the PCM (Powertrain Control Module) experiences a low voltage situation that involves the number nine (in the firing order) cylinder’s fuel injector.

What the P0285 code means

The fuel injector could be experiencing problems for a number of reasons, but if you’re seeing the P0285 it indicates that it’s malfunctioning which means further problems could be on the way. Whenever a fuel injector malfunctions, it sends a ripple effect down the line, meaning your entire engine could be affected because of the mixed signals the PCM is receiving. One example would be if the fuel injector spray pattern is lessened. As a result, you’ll end up with a lean mixture – the beginning of the ripple effect. Next, the oxygen sensor sends a signal regarding the lean mixture to your vehicle’s PCM. In return, it ensures the fuel mixture is enriched to all cylinders. The upshot is that your fuel economy will plummet. The cylinder with the malfunctioning injector creates a lean mixture that, in turn, makes for a high cylinder head temp that results in detonation. The knock sensor picks up on the detonation and sends a signal about it to the PCM. It responds by slowing the timing, so now your engine lacks power and runs rough. We could go on and on about this type of ripple effect, but the general idea is that one small problem can have a huge impact if not addressed in a timely fashion.

What causes the P0285 code?

Possible reasons you could be suffering from issues related to the P0285 code are:

  • Malfunctioning fuel injector
  • The fuel injector has become plugged
  • The number nine cylinder is being supplied by a dirty fuel injector
  • The fuel injector harness has an open or a short
  • The fuel injector connector is loose or corroded

As you can see, you can’t underestimate the fuel injector’s role in the performance of your vehicle. Making sure it’s cleaned regularly will help you avoid a lot of problems.

What are the symptoms of the P0285 code?

If your vehicle logs a P0285, expect that a Check Engine Light will come on too. Until you get it fixed, your engine will most likely run pretty rough. As we mentioned above, your fuel economy will most likely suffer as well – something that will get worse with time. When you try accelerating, the associated problems will slow you down and may even cause a rattling sound.

How does a mechanic diagnose the P0285 code?

Your mechanic will most likely begin by taking a look at your vehicle’s fuel injectors for the guilty party. They’ll use a DVOM to assess their resistance. If they all check out, they’ll move onto looking for a problem with the electrical components of your vehicle. It could be an issue with the wiring of your starter solenoid, alternator, oxygen sensor, etc. Even something like a high-powered stereo or some other third-party part that was installed incorrectly could cause the P0285 code.

Common mistakes when diagnosing the P0285 code

The biggest mistake you could make is simply not giving the fuel injectors enough attention. A fuel injector is almost always responsible for this code. If it does turn out to be a problem related to the stereo you installed or something similar, be sure it’s rewired correctly so this issue doesn’t happen again.

How serious is the P0285 code?

Although it’s not an incredibly serious problem, it will make getting around inconvenient until you address the issue behind the code. However, if you leave the P0285 code long enough, it could evolve into something much worse.

What repairs can fix the P0285 code?

  • Cleaning, repairing or replacing a dirty/malfunctioning fuel injector
  • Addressing any problems with the wiring or connectors
  • Fixing problems with the harness connector and its pins

Additional comments for consideration regarding the P0285 code

Even if a bad injector is responsible for the problem, the entire engine should be checked for any other damage it may have caused. This will curtail the chances of future problems.

Need help with a P0285 code?

Call YourMechanic today at 1-800-701-6230 if your vehicle has logged a P0285 trouble code to speak with a service advisor. You can also schedule an appointment online. Either way, we’ll provide you with a quote get a certified mobile mechanic out to your home or place of business ASAP.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...

Related questions

Q: Car wont start

Have the vehicle scanned and see if there is any engine codes. If you have codes then have them diagnosed first in order to more easily pinpoint the problem. If you are getting cam or crank sensor codes, then look...

Q: Van not starting. Only starts after sitting.

I would first recommend enlisting the help of a professional to scan your vehicle for trouble codes. The check engine light may be related to your issue. The issue you are having may be related to your cooling system since...

Q: Fuel System?

A whirring noise is actually a common symptom of a failing fuel pump. You can rule the power steering pump in or out just by disconnecting power steering belt. Obviously, if the noise remains the same with pump disconnected, then...