MODS (Mark): This is what I was talking about, if after running all your tests we come up with different results and confirm my theory we can keep this up or maybe add it to the everything you need to know thread, if not we can always delete this, I wont be mad. I'll edit for additional content if anything becomes available or apparent.
The Long (My English teacher would be so proud) Version:
So I have been fighting an issue with my dead #5 cylinder for quite some time now, I did all of the normal procedures, tested all of the components and was left scratching my head as the New Style PTU test procedure is not listed in the FSM that's all over the internet. Hellbent on trying to find why my cylinder was not firing but had spark and fuel and compression I went a searching and here is where I have ended up. When you first discover that you aren't running on all 6 you do the Power Balance Test and discover that you have a pesky dead cylinder or two, from here you go through the usual
- Test for fuel
- Test for spark
- Test for compression
Everything comes out as it should, so you are stuck scratching your head, calling your more mechanically inclined friends, even taking the chance on trying to get something out of the techs at the dealer but nothing! well here is your fish, enjoy it. Most of the time when a PTU fries it does just that, its simple to tell. But sometimes like in my case, due to a hellatious short I had in my power wire some time ago the PTU did not fry but got just crispy enough to get out of spec and with the unavailability of a diagnosis and test page from the updated FSM you are stuck guessing and perhaps throwing down cash on a part you don't need. Well low and behold, the page that so many of us could benefit from
The Short Version:
Use this diagram to test your New Style PTU to make sure it is within spec if the following happens to you:
1. you start misfiring
2. you do power balance test and find the dead cylinder or cylinders
3. you check for fuel and confirm working injector/injectors and pressure
4. you pull COP and Plug and test by conventional method of grounding on manifold
A weakened/slightly burned PTU will deliver spark but will not deliver it at the strength or duration required for combustion and will cause dead cylinders to occur where by every other test there should not be.