Code P0340, 30 amp fuse blowing, very rough idle

Tiny
JESSE6101
  • MEMBER
  • 2002 JEEP GRAND CHEROKEE
  • 4.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
Did timing chain guides and tension-er's on my vehicle and put it all back together now it will start and run, has hesitation when I push the gas then revs up beautifully then idles good for five seconds then all of a sudden misses like crazy and shuts down blowing the PCM 30 amp fuse. It runs good for the first ten to twenty seconds after start up. Only code showing is the p0340 cam sensor code. Cam sensor has been replaced as well as all eight coils and plugs and the battery. Nothing that has been replaced has had any effect on the issue. I am wondering if this sounds like a wiring issue or if the timing is off a tooth and where would it be off? The only issue the vehicle had prior to the first tear down was the oil pickup and filter was clogged with what was left of the timing chain guides. Two tension-er's were replaced and the third one was still good. I am thinking the cams are off one tooth but would that cause the PCM to blow a fuse?
Wednesday, May 30th, 2018 AT 7:28 AM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hello,

It does sounds like the timing is off one tooth which will cause the camshaft code. Also it sounds like you have pinched some wires in the engine harness which will make the PCM fuse blow.

Here are guides for the timing chain so you can recheck your work.

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken
Was this
answer
helpful?
Yes
No
Thursday, May 31st, 2018 AT 11:26 AM
Tiny
JESSE6101
  • MEMBER
  • 27 POSTS
Okay, so in the mean time yesterday I tore it back down and found the cams were off so I re-timed them and it started up and still runs rough and has a miss. Sounds like timing still but it is still blowing the PCM fuse. And now I am getting code p1391 and not p0340.
Was this
answer
helpful?
Yes
No
Friday, June 1st, 2018 AT 5:36 AM
Tiny
JESSE6101
  • MEMBER
  • 27 POSTS
I also did the wiring tests for ohms and volts and everything seemed to check out.
Was this
answer
helpful?
Yes
No
Friday, June 1st, 2018 AT 5:38 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I am wondering if you left a ground off? It never blew the fuse before the job? Here are engine wiring diagrams and a guide to help you test for a grounded circuit:

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

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken
Was this
answer
helpful?
Yes
No
Friday, June 1st, 2018 AT 7:51 PM
Tiny
JESSE6101
  • MEMBER
  • 27 POSTS
Okay, I just hopped in the Jeep to start testing wires and I now have a p1698 and p1391. It runs fine for a minute then misses like crazy then I rev it up when it has cleared up and misses at about 3000 rpm. I did check flat ground cables and they look good and hooked up. I am 99% sure the timing is right cause I just tore it back down and re timed the cams with engine on TDC.
Was this
answer
helpful?
Yes
No
Saturday, June 2nd, 2018 AT 4:05 PM
Tiny
JESSE6101
  • MEMBER
  • 27 POSTS
Found a ground wire coming from the PCM that was pulled loose, fixed that and it did not blow a fuse as quick when I started it back up, but this is how it is running now: Random bad miss at idle, bad hesitation when I press the gas then when revved up it sounds like it hits a rev limiter at 4,500 rpm's.
Was this
answer
helpful?
Yes
No
Sunday, June 3rd, 2018 AT 7:00 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yes they only rev so high then the PCM stops it. I know it has nothing to do with the fuse problem but can you do a compression test to make sure the engine is not hurt?

https://www.2carpros.com/articles/how-to-test-engine-compression

What fuse number is it that blows? I will look at everything on the circuit to fix that problem.

Please let us know what happens.

Cheers, Ken
Was this
answer
helpful?
Yes
No
Sunday, June 3rd, 2018 AT 11:25 AM

Please login or register to post a reply.

Sponsored links