Fuel Injector Open Cyl 5

BLS

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Mazda CX-9 Grand Touring
Just having an issue with the 2009 CX-9. Wife reported a check engine light and running rough. After work I read the OBDII codes and got #5 fuel injector open error. Starting again from cold it ran fine so I erased the codes and started driving home. After a stop to eat (warm engine?) I got the CEL and the code again. Was able to gently drive home minimizing vibration by using lower gears.

Questions:

1. Is this an expected failure at 10 years and 125000 miles?

2. Since it is showing an "open" does that indicate an electrical vs mechanical issue with the injector?

3. I think #5 is on the back row so I will need to remove the air plenum--so--should I go ahead and replace all injectors at one time?

4. Is it worth doing just a unplug, spray with DeOxit, replug or should I plan on just replacing the injector (s)?

Any experience or advice appreciated.


Brian in Manassas VA
2009 CX-9 Grand Touring FWD
 
Just having an issue with the 2009 CX-9. Wife reported a check engine light and running rough. After work I read the OBDII codes and got #5 fuel injector open error. Starting again from cold it ran fine so I erased the codes and started driving home. After a stop to eat (warm engine?) I got the CEL and the code again. Was able to gently drive home minimizing vibration by using lower gears.

Questions:

1. Is this an expected failure at 10 years and 125000 miles?

2. Since it is showing an "open" does that indicate an electrical vs mechanical issue with the injector?

3. I think #5 is on the back row so I will need to remove the air plenum--so--should I go ahead and replace all injectors at one time?

4. Is it worth doing just a unplug, spray with DeOxit, replug or should I plan on just replacing the injector (s)?

Any experience or advice appreciated.


Brian in Manassas VA
2009 CX-9 Grand Touring FWD

Was the code P0205?

Check the resistance of the injectors with an ohmmeter. They should be the same, within a half an ohm or so (I think the "correct" value on the OEM Mazda is ~12 or 13 ohms). Hopefully, the bad one will be obvious. I don't know that I'd recommend replacing all of them, but that's up to you.
 
You could try swapping the coil on cylinder 5 with a different coil on a different cylinder and see if the code follows, for example if you swap cylinder 2 and cylinder 5 and you get a P0202 code it means the injector was faulty, but first you should visually check the wiring
to the coil on cylinder 5 for any signs of damage.
 
OK, however I replaced all 6 coils about a year and a half ago so don't suspect them as much. I will check the resistance values.

BLS
 
You could try swapping the coil on cylinder 5 with a different coil on a different cylinder and see if the code follows, for example if you swap cylinder 2 and cylinder 5 and you get a P0202 code it means the injector was faulty, but first you should visually check the wiring
to the coil on cylinder 5 for any signs of damage.

Just to be clear, you're talking swapping coils.

In your example, if the code goes from P0205 to P0202, that means the coil is bad and injector is likely OK.
 
OK read the codes: P0205 Cylinder #5 Injector Circuit Open, P0305 Cylinder #5 Misfire, P0174 System too Lean bank 2.

I have 6 new injectors on hand. Will post resistance readings but will probably just replace all 6 while I have the rail off.
 
Funny I had the exact same issue last week, #5 injector @71000 miles. It's the front middle cylinder, but you have to remove the fuel rail to get to it, so intake manifold comes off. If you didn't replace the plugs you might as well do them now. I don't think it is necessary to replace all 6 injectors, just the bad one. Mine went bad halfway through a 200 mile trip. Checked resistance when I got home and it was 2000 ohms. The next day when I checked it in the morning it was 20 ohms, all the others were 13 ohms. Apparently heat causes it to open which is why you don't have a problem until it warms up. Took about 3 hours.

I followed http://davidcwatson.com/auto/mazda/repair/fuel-injector/
 
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Yep. Got all 6 out after a struggle. Readings in ohms were (from left to right facing the engine) engine stone cold.

Back row 12.4 12.3 12.4
Front row 12.4 88.4 12.4

Measured a brand new Bosch injector 11.4

BLS

I'm going to change all six since it's a hassle getting in there.

The tips above the nozzle all had some black gunk on them but the holes seemed uniform to the naked eye.
 
OK, job is done. The link from JJW6645 above is very useful as is this: https://www.youtube.com/watch?v=l-7Cqd6cO7k

I used Bosch W0133-2618710 injectors from Partsgeek.com Perfect replacement. I installed and clipped the injectors to the rail then pressed each injector back into place with a lot of force. I sprayed all the connectors with DeOxit on reassembly. New green intake manifold gaskets.

I never did really depressurize the fuel system but had very minimal fuel from the rail connector and each injector during removal. After reassembly I just cranked a couple of times and then it started with a couple of hickups, then ran smoothly. No more codes.

This job is slightly harder than a plug and coil change but well within most people's ability.
 
thanks for the followup, this will certainly help others in the future. The joy of forums, information that actually stays.
 
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