SPONSORED LINKS

Trouble code P0304

Tiny
BSCHRUM
  • MEMBER
  • 2005 CHEVROLET COLORADO
  • 92,000 MILES
Two weeks ago the vehicle developed a misfire. Scanner gave a P0304 code stating cyl. No. 4 misfire. Replaced the coil which cleared the problem for two weeks. Same problem - same code. Part store exchanged the coil. Installed new coil but misfire still there. Swapped coils on cylinders - problem stayed on cyl. 4. Checked wiring and found nothing. Have +12v on pink wire - ground on black - looks like pulses on green wire (at least #4 looks like the other cylinders). Pulled PCM off firewall to inspect it - found nothing obvious. After putting PCM back cyl. 4 still misfiring, door locks do not work, driver's window will not move, and clock reset to 1200. Do I have a bad plug at the PCM or do you think there might be other issues?
SPONSORED LINKS
Monday, November 28th, 2011 AT 7:41 PM

11 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
Did you try swapping the plug with another cylinder too?

Take a compression test also.
Was this
answer
helpful?
Yes
No
Monday, November 28th, 2011 AT 8:10 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
First of all, you missed the obvious. try changing the spark plug and I bet your issue with the 304 is gone
If not you will need to get a noid light to be sure the injector is getting pulse. If getting pulse,spark and has good compression the injector may be bad/not squirting fuel

See the guides below, they will help

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

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

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Roy
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
-1
Monday, November 28th, 2011 AT 8:12 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
You shouldn't have any programming problems with the PCM. It will lose the adaptive memory and any codes stored but that should be all.
Was this
answer
helpful?
Yes
No
Monday, November 28th, 2011 AT 9:04 PM
Tiny
BSCHRUM
  • MEMBER
  • 4 POSTS
Changed the spark plugs with the new coil with no improvement. Compression is good. Did not disconnect the PCM - just detached it from the firewall (plastic fingers).
Was this
answer
helpful?
Yes
No
Tuesday, November 29th, 2011 AT 3:55 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
If the spark is good, compression is good, that only leaves the fuel injector. You can try moving that injector to a different cylinder to see if the misfire moves with it.
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Tuesday, November 29th, 2011 AT 10:48 AM
Tiny
BSCHRUM
  • MEMBER
  • 4 POSTS
Thought about the injector too. I was probably not clear. I changed the spark plugs but still have no spark out of four. I put a plug in the coil out of the cylinder to check that. Checked all the voltages on the plug but not sure if I am seeing pulses on the green wire. That is the wire that goes back to the PCM. With all the other issues (door locks, driver's window, and radio) I am still wondering about the plug going into the PCM.
Was this
answer
helpful?
Yes
No
Tuesday, November 29th, 2011 AT 2:44 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
If you have power and pulse to the coil, you should have spark if the coil is good, assuming you are grounding the spark plug or using a spark tester which is what you should be doing.
Was this
answer
helpful?
Yes
No
-1
Tuesday, November 29th, 2011 AT 8:03 PM
Tiny
BSCHRUM
  • MEMBER
  • 4 POSTS
I know I have power and ground but I am not sure if I have pulse to coil. Any down and dirty way to test that?
Was this
answer
helpful?
Yes
No
Tuesday, November 29th, 2011 AT 10:24 PM
Tiny
ZIPPYRAIN09
  • MEMBER
  • 2 POSTS
My 05 Chevy Colorado have the same thing about the driver window and the locks and there is no spark on cylinder 4 I tried a lot of stuff and nothing did you find out what was the problem? I think I’m gonna go for a computer and see what happens
Was this
answer
helpful?
Yes
No
Wednesday, January 30th, 2019 AT 5:10 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
If you have a scope, you can check the signal from the coil to the PCM. You cannot tell with a voltmeter or test light.

Check the wiring back to the PCM from the coil.

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

Roy
Was this
answer
helpful?
Yes
No
Wednesday, January 30th, 2019 AT 5:26 PM

Please login or register to post a reply.

Related P0304 Content

Sponsored links