Transmission issue

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Chris81593

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I've got a 2004 LS V8 with 158k, today it started running rough at low rpm and eventually gave an MIL. I noticed at this point it seemed to be skipping a gear so I put it into sport mode and found that the car will not go into 3rd gear. It skips right over it from 2nd to 4th. The code stores within the computer is P0356: Ignition coil "f" primary/secondary circuit malfunction. It does not have the smell that is associated with a dead coil. Any help is appreciated.
 
I've never had any smell with failed coils. With a P035x code fuel is cut to that cylinder for sure. Best to solve ignition problem first.
 
IMG_0042.JPG
If the valve cover gasket is leaking, oil could fill the spark plug well and cause premature coil failure. Cylinder #6 is second from the front on the driver side.
 
Chris81593 said:
I replaced the complete set or coils about 20k miles ago. ...
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What brand of coils? Did you replace the spark plugs at exactly the same time? Did you set or verify the gap on each plug was 1.0mm?
 
joegr said:
What brand of coils? Did you replace the spark plugs at exactly the same time? Did you set or verify the gap on each plug was 1.0mm?
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They're motorcraft coils. I did not do the spark plugs as they had been replaced shortly before I purchased the car. It had 103k on it at the time. Probably worth checking out again at this point
 
The problem is that bad coils can kill plugs, even new ones, and in a very few miles. The nearly new, but now damaged plug can then kill the new coil. Replace both at the same time, or risk running in this circle forever.

That said, this may not have happened. The first thing to do is to verify that the connector on the coil is fully latched in. The latches break very easily, and a loose connector would trigger the code that you have (as would a bad coil or a wiring fault).
 
joegr said:
The problem is that bad coils can kill plugs, even new ones, and in a very few miles. The nearly new, but now damaged plug can then kill the new coil. Replace both at the same time, or risk running in this circle forever.

That said, this may not have happened. The first thing to do is to verify that the connector on the coil is fully latched in. The latches break very easily, and a loose connector would trigger the code that you have (as would a bad coil or a wiring fault).
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That's a good point that I hadn't even considered. Makes perfect sense that they could easily affect one another. Is there any benefit on these cars between platinum and regular plugs? I only ask because I had a truck that if platinum were used it would run too hot and short out
 
Factory manual calls for platinum. Just stay away from Bosch.
 
Replacing the coil and plug fixed the issue temporarily. I've been about 350 miles and the problem has already resurfaced. Is there another cause for this code or do I just have back to back defective coils?
 
Well, you could have two bad Motorcraft coils in a row, but probably not. (The same though does not apply to those e-bay coils, including the ones that try to fool you into thinking they are OEM. Those are likely to be bad.)
Another possibility is damaged wiring and/or a connector that is not correctly latching into the coil. If you tug on the wire and the connector comes out, then it is not correctly latching. P035x is an electrical continuity code. It should be coil, wiring, or PCM.
 
joegr said:
Well, you could have two bad Motorcraft coils in a row, but probably not. (The same though does not apply to those e-bay coils, including the ones that try to fool you into thinking they are OEM. Those are likely to be bad.)
Another possibility is damaged wiring and/or a connector that is not correctly latching into the coil. If you tug on the wire and the connector comes out, then it is not correctly latching. P035x is an electrical continuity code. It should be coil, wiring, or PCM.
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If it happens to be damaged wiring, is it possible to replace the harness that connects the coils together? Or is a complete wiring harness that is needed?
 
Individual repairs to the harness are practical, no need to replace all of it.
 
Spliced in a new set of cables and connector on cylinder 6. Replaced the plug and coil at the same time. The problem is still there. Is all that's left the pcm? I know that there are currently none in stock in the USA
 
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joegr said:
Factory manual calls for platinum. Just stay away from Bosch.
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OUCH.
I just installed a set of Bosch Double Platinum in the V6 Getrag I'm rebuilding. Why should I have avoided them?
 
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I have had bad experiences with Bosch + Ford, and from what I have seen, I am not alone in this.
 
Chris81593 said:
I've got a 2004 LS V8 with 158k, today it started running rough at low rpm and eventually gave an MIL. I noticed at this point it seemed to be skipping a gear so I put it into sport mode and found that the car will not go into 3rd gear. It skips right over it from 2nd to 4th. The code stores within the computer is P0356: Ignition coil "f" primary/secondary circuit malfunction. It does not have the smell that is associated with a dead coil. Any help is appreciated.
Click to expand...
 
Here's some valuable info that my son wrote to Conchita, on LSO Facebook. I think he's an LS expert becjause of all he has researched and all the work he taught himself how to do on his work LS.


  1. Conchita Porter: it depends what he means by doing a jerk. If it's dropping out of gear at low speeds or a full stop and he has to give it a little gas before it'll go then it would cause it to jerk when the tranny reengaged - caused by low fluid. If it stays in gear but either grinds or shifts really hard only sometimes while driving then it's worn servos and the cheapest option is to replace them with modified servos from a guy on LVC. As far as I know a bad solenoid will usually cause it to shift harder and slower than normal but not as hard as a bad servo - any LS 05 or older should have the solenoid, fluid, and filter changed out anyway cuz ford was using bad fluid that would clog the filter and cause the solenoid to overheat until failure. While that's being done, you might as well have the 3-4 spring replaced cuz the part literally costs $5 and takes about 5min additional work to replace if you're already doing a solenoid.

To fill fluid correctly... fill transmission from the center screw-out piece of the drain plug itself until fluid comes back out, start the car and let it warm up at idle then add more fluid, cycle through P-R-N-D5-D4-D5-N-R-P holding each gear for a few seconds and fill it again until fluid comes out, take it for a drive (about a mile) then cycle through all gears again and FINALLY you'll be able to fill it up until fluid comes back out in a steady stream and have it accurately filled. If the fluid is only dripping out then it's still low, it should be like running a faucet. I have never talked to anyone in any shop I had taken my moms LS to when I had it that knew how to do this correctly so I would be surprised if your guy was any different.


Btw, I personally recommend Royal Purple ATF (mercon V compatible) and their HPS line for engine oil. I put their ATF in my moms transmission, power steering, and hydraulic fan. The power steering and hydraulic fan pumps got consistently and significantly quieter, steering was smoother, and I'm convinced that it's basically the only reason the transmission wasn't damaged after it was filled incorrectly and was driven for about 3 weeks while 2.5 quarts low. Also, the mpg went up by 2 overall and the timing chains stopped making noise for almost 3 years when I switched from mobile 1 to royal purple HPS.


  1. This is not correct. It's a sport so you have to have a select shift transmission for it. Additionally, there were updates to the transmission every year so you need a 2002 V8 sport transmission specifically. To make things worse, there was a mid model year update for 02 and I don't know if anything was messed with in the transmission. You'll have to do some research to figure that one out. That said, it's very rare for these transmission to actually fail as opposed to just being in need of a relatively simple fix that mimics the symptoms of something much more serious.
 
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