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Misfire and code P0302

Tiny
AVALON1995
  • MEMBER
  • 1995 TOYOTA AVALON
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
2CarPros,

I have a misfire code, which is P0302. After doing various diagnoses, it has been definitely determined that the issue is with a bad ground wire on the fuel injector connector on the cylinder with the misfire code.

I replaced the entire ground wire for that cylinder with the misfire code from the fuel injector connector all the way to the ECM just to be sure, even though I didn't even see a broken or chewed up wire. This didn't resolve the issue.

The car has a V6 cylinder and I also diagnosed the other 5 fuel injector connectors. The ground wires for all those 5 fuel injector connectors are fine.

Since replacing the ground wire didn't resolve the issue, is there anything you can suggest I try out at this point?

For the time being, as an alternative method, I decided to splice and share the functional ground wire from the adjacent cylinder. In other words, I now have two fuel injector connectors sharing the same ground wire. This method has worked and has resolved the misfire issue. However, my concern is if this method is an acceptable resolution or is there any type of downside or hazard this could cause? Preferably, I would much rather have a dedicated ground wire for the cylinder with the misfire code instead of sharing a ground wire from another cylinder. Thank you very much for any help you can provide.
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Friday, July 3rd, 2020 AT 11:43 AM

21 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

The ECM is what controls the ground for the injectors.

When you shared a ground and the misfire went away, that tells me the ECM is not good. The quad driver for that cylinder is failed inside the ECM.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Roy

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Friday, July 3rd, 2020 AT 12:23 PM
Tiny
AVALON1995
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So, is sharing the ground wire a sustainable method of resolution? Is there any type of downside I should be concerned about?

In terms of the faulty quad driver for that cylinder in the ECM, is it preferred to replace the quad driver or replace the entire ECM? A used OEM Engine Control Module goes for $20.00 to $40.00. If I replace the ECM with a used OEM, does it need reprogramming? If so, how much would it roughly be? Thank you!
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Saturday, July 11th, 2020 AT 8:44 AM
Tiny
ASEMASTER6371
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You cannot share a ground for the injector. They each have there own wire to the ECM.

You could try a used one but I never suggest used modules for any car as they may be worse than the one you have.

I attached the replacement from rock auto for you.

The ECM is a plug and play. No programming required at all.

Roy
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Saturday, July 11th, 2020 AT 9:06 AM
Tiny
AVALON1995
  • MEMBER
  • 121 POSTS
So, even though, the misfire went away as a result of sharing a ground wire, you don't recommend to drive the car with that type of setup? Thank you!
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Saturday, July 11th, 2020 AT 2:12 PM
Tiny
ASEMASTER6371
  • MECHANIC
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No, I do not. You are adding fuel at the wrong time and that will effect emissions as well as drive ability.

Also, it will not stay that way. It will totally fail at some point due to the internal failure. It is not a matter of if, it is a matter of when.

Roy
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Saturday, July 11th, 2020 AT 2:42 PM
Tiny
AVALON1995
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  • 121 POSTS
Are the fuel injectors in this car ground wire controlled or power wire controlled?
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Friday, July 31st, 2020 AT 12:36 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
They are ground controlled by the ECM. The power is supplied to the injectors from the fuse box. The other wires go to the ECM and they are grounded to allow fuel at the correct time.

The power is supplied by a 7.5 amp fuse in the fuse box.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy
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Friday, July 31st, 2020 AT 3:58 AM
Tiny
AVALON1995
  • MEMBER
  • 121 POSTS
So, I understand that the ground wires for the fuel injectors are connected to the ECM and the ground wires for the ignition coils are connected to the igniter. While power is supplied by a 7.5 amp fuse in the fuse box, where exactly are the power wires for the fuel injectors and the ignition coils connected to? Also, where is the fuse box where power is being supplied? Is there an individual fuse for each power wire or is there just one fuse for all of the power wires? Thanks!
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Friday, July 31st, 2020 AT 11:27 AM
Tiny
ASEMASTER6371
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The power comes off a splice that feeds all the injectors.

I attached the diagram and location of the fuse block for you.

Test for power on both sides of the fuse.

Roy
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Friday, July 31st, 2020 AT 12:05 PM
Tiny
AVALON1995
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  • 121 POSTS
So, when you say test for power, do you mean the fuse you circled in red? Also, when you say both sides of the fuse, are you referring to what I circled in red in the attached picture? Apparently it's a 5 amp fuse, not 7 5 amp. Is there a way you can resend a better version of the picture you sent on the left? It's really not legible. The one on the right is great. Thank you!
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Friday, July 31st, 2020 AT 1:35 PM
Tiny
ASEMASTER6371
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Yes, test the terminals circled with a test light with the fuse installed, key on with a test light.

Attached the enlarged picture.

Roy
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Friday, July 31st, 2020 AT 1:43 PM
Tiny
AVALON1995
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  • 121 POSTS
I think you forgot to attach the picture.
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Friday, July 31st, 2020 AT 2:10 PM
Tiny
ASEMASTER6371
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Sorry, I did but I failed to verify it.

Roy
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Friday, July 31st, 2020 AT 2:18 PM
Tiny
AVALON1995
  • MEMBER
  • 121 POSTS
Where is this fuse box for the last picture you sent located? I know where the other fuse box is located, the one where you had circled.
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Friday, July 31st, 2020 AT 2:47 PM
Tiny
AVALON1995
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I wanted to point out something in reference to the earlier threads about sharing a ground wire with 2 injectors. Well, I have observed that even though the check engine light for the misfire code has not been triggered and the symptoms of a misfire haven't emerged as a result of sharing one ground wire with two injectors, the car tremendously lacks power. It's like the car is incapable of going past 40 mph and when it comes to even a moderate incline road, then it's pretty much hopeless. Hence, it appears that driving this car with just 5 cylinders is somehow a better option despite the misfire that will be present. So, what do you think about this? While I understand that replacing the ECM would potentially resolve everything, I'm just trying to figure out if one had the option of driving this car with just 5 cylinders versus driving with 6 cylinders, while one ground wire is sharing with two injectors, which option would be the better one and why?

Thank you!
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Friday, July 31st, 2020 AT 3:25 PM
Tiny
ASEMASTER6371
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ECM replacement is the only option. You cannot share grounds as the current flow is only set for one injector only. You will damage the ECM even more by doing this or leaving this connection.

You will be overloading the quad driver in the ECM and will result in total failure of the ECM and the engine running.

Roy
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Friday, July 31st, 2020 AT 3:41 PM
Tiny
AVALON1995
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  • 121 POSTS
I appreciate your explanation of the downside of sharing a ground wire with two injectors. What I'm now trying to understand is, what would be the downside of driving this car with just 5 cylinders (each cylinder having its own ground wire and no sharing involved)?

Thank you!
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Friday, July 31st, 2020 AT 5:20 PM
Tiny
AVALON1995
  • MEMBER
  • 121 POSTS
I appreciate your explanation of the downside of sharing a ground wire with two injectors. What I'm now trying to understand is, besides a misfire, what would be the downside of driving this car with just 5 cylinders (each cylinder having its own ground wire and no sharing involved)?

While I understand that an ECM replacement is the only and best option, until I have the money to buy a new ECM, what would be the lesser of two evils between the following?

1) Driving with 6 cylinders, while 2 injectors
are sharing one ground wire.

2) Driving with just 5 cylinders (each cylinder having its own ground wire and no sharing involved), and of course, a misfire code existing

So, is the lesser of two evils #1 or #2?

Thank you!
.
Cheers!
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Saturday, August 1st, 2020 AT 11:41 AM
Tiny
ASEMASTER6371
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Number 2 is the lesser of 2 evils but with the misfire from number 2 you could damage the catalytic converter.

Roy
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Saturday, August 1st, 2020 AT 1:38 PM
Tiny
AVALON1995
  • MEMBER
  • 121 POSTS
Thank you so much! In addition to possibly damaging the catalytic converter, I presume there will surely be an increase in fuel consumption with a misfire, right?
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Saturday, August 1st, 2020 AT 2:49 PM

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