Hi members,

I had my car packed up to the ceiling with Christmas presents and luggage to go on vacation and as I started the car up to pull out of the driveway I threw a P0351 check engine code.
What are the odds?
I'm so grateful this happened now and not on the road but this error code kicked my a** for 5-6 hours and I do DC diagnostics for my job.
Had to go in much deeper than I wanted to see what the heck is going on.

Long story short the car was barely idling and then ran good and then bad- something was dying but all I had was that one code.
So I pulled the intake manifold and swapped out coil pack #1. Fun!!! lol
Put it all back together and the P0351 code came back on instantly upon starting the engine and car still ran badly and in limp mode so after a lot of diagnostics I thought I had a bad ECM the way it was acting intermittently.
In the end- problem was traced to a faulty/dying coil pack #2(front bank!) shorting the IGF feedback for ALL coils- so my scanner basically lied by not telling me the whole story.
End of story- sometimes if a coil pack fails in a special way a P0351 is really a P0351, P0352, P0353, P0343, P0355, P0356 but the ECM leaves the extra codes off. This could lead to a replacing a coil pack on the wrong cylinder and possibly an ECM by mistake when it was neither.

>> If I knew then what I know now it would've been a 10 minute repair so I am sharing my work below for anyone who needs it...

 

ugh! that doesnt sound like fun at all!!! sounds a bit too complicated for me to endure! but yea better at home then possibly stuck on the road somewhere in the middle of b.f.e (most of u should know what that means)

 

Nice post. Getting at those bank 1 plugs/coils is a character builder! Did you also remove the cowling, or just the manifold?

I had a zero compression case (broken exhaust valve spring), and did a similar thing chasing misfire codes all over the place, compression test told the story...

 

so does this mean all 6 coil packs burned/shorted out and had to be replaced?

 

I saw your thread on the RX350 engine removal and work you did and it was an incredible job with massive cringe effect for how much work that appears to be without the luxury of a car lift. My biggest fear would be that the machine shop missed something and the engine would have to be pulled again and not having a 2nd car that's a job I would have to hire someone to do if that happened to me.

On the RX330 since I don't install the rear manifold support bracket bolt I don't have to remove the cowling(just a push in & pull up motion for me) but since I removed the manifold once to swap the coil pack and a 2nd time to inspect wiring since still throwing code for cylinder #1 yeah that sucked when it was coil #2 on front bank that was causing all the problems...

 

Only the #2 coil pack was shorting intermittently but it was shorting in a way that it was grounding all the feedback pulses for all the other coil packs and because of this the ECM should've reported all the other coils bad too- since there was no feedback pulses for any of them.

Once I realized this it was fixed in 10 minutes by pulling the coil pack plugs one at a time until I had my 5V back and pulsing on pin 2.
PS- bad coil cylinder #2 had a crack in it when I located the problem- should've pulled all coils for inspection first. yeah I feel dumb now but I trusted my scanner too much and cost me a lot of aggrevation. lol

 

yea it only goes to show ya that sometimes even electronics that are supposed to help ya dont always help the situation and unfortunately sometimes make things worse than better.

 

Great you figured it out....Yea lot of times the diag takes a longer to do, but at least your not just throwing parts at it as many ppl do........

 

true that!! nothing worse when it comes to vehicle repairs to throw parts/money at it only to find out ya got the wrong part etc

 

Just got back from a 1,500 miles trip and car hasn't run this good in months.
All the slightest engine vibration is gone and can barely feel car running so I think this coil has been throwing weak spark too for a while before it finally died.
Forgot to take pic of cracked cylinder #2 coil pack before I left so here is something to look for on all front plugs before removing manifold on a P0351 code and maybe get lucky- and if they do have to pull manifold may want to inspect all coils while in there so you don't go thru what I had to.


Dead/Dying coil...

 

thanks for the info and pics on this so i know what to look for if i have a suspected bad front coil pack at some point.

 

So I'm having a similar issue on a GX460 and used this post to do some debug.

It seems like if there is a bad plug that IGF/pin2 would be pulled down on ALL harnesses? And if you disconnect the bad coil then IGF/pin2 should show 5V on any harness?

What I am seeing with my issue:
on #1 wiring harness (disconnected from coil) I have 12V power, but never see 5V power on IGF.
I've tried this with all other coil harnesses connected, and I tried with #3 disconnected.

on #3 wiring harness (disconnected from coil) I have 12V power, the 5V on IGF, and the pulse on IGT.

I'm having trouble reconciling how one of the other coils would be bad if the #3 harness IGG/pin2 has 5V while #1 harness does not.

This seems like a short with the #1 wiring or ECM, right?