Hi!
Longtime Nissan owner here.
Just got a 2006 X w/180K mi a couple weeks ago.
It had the dreaded PO300 (multiple cylinder misfire) when I bought it cheap.

I have cleaned all the grounds, replaced the battery neg cable, all new plugs (NGK), coils, MAF, ECM relay, fuel injectors, knock sensors, 02 sensors, LIM and upper gaskets, cleaned the TB, and probably something else I forgot.

That cleared up the PO300 and occasional knock sensor codes, now I am stuck with the PO305 and occasional PO132 High volt (rich) bank 1 (which leads me to assume the brand new injector is OK since I hate taking off that manifold). I swapped in 3 different coils and spark plugs and all the same PO305.
I have tested the coil harness ground and it's good, and has 12V+. I can't test the violet signal wire for signal yet since I don't have a Hz meter or oscilloscope, but it seems to have about .5 volt (should have 5v?).

Fuel pressure is 51# .

All the grounds were pretty ugly, the battery neg cable looked like it got pretty hot.
Looking at a new ECM?
Any ideas?
Thanks

Ordered
23731-AL61A Crank sensor

23731-6J90B Bank 2 cam sensor

23731-AL60C Bank 1 cam sensor

Iv'e got nothing .. sorry

Turns out the bank 1/passenger catalytic was failing. Eventually the secondary catalytic clogged and the problem became obvious. Failure mode went from cyl @5 to cyl #3 misfires also.

I replaced the catalytics, punched out the secondaries, and installed a Dynomax stainless catback.
Runs great now!

Need to perform the Mixture Ratio Self Learn procedure, and that may remove the pesky P2A00 code.
https://www.nissanhelp.com/diy/altima/p ... arning.php

Failure mode was: The ground for the coils corroded and caused a Bank1 misfire which in turn caused the catalytic to fail.
Also had a filthy MAF/rich condition from previous owner's use of K&N junk.
Coolant temp sensor was bad too.
I'd say all of those contributed to the melted converter.

Nice investigative work, Squee!

Not sure how I missed this one, but I went through that with our 97 Pathy... no corrosion on the body but the grounds were almost completely nonexistent!

Glad you found the culprit.

How does the truck sound with the Dynomax stainless catback? Can you hear the engine on the freeway in final drive gear going to 70 MPH. I know I will probably need to replace my exhaust soon but I drive this truck back and forth to LA and don't want the loud sound like I have in 300ZX which sounds great on short rides wiht the Tops off.

Sorry for the delay BadQ45t.
Dynomax 19443* is a loud 'braaap' when you hit the throttle, but quiets down at low throttle input.
Rather quiet at freeway speeds.

I was looking for a solution and someone with the same problem said he added a couple of resonators ahead of the muffler. Which is the only place to fit one anyway.
I am looking at pulling the deleted secondary cats and butt splicing in a couple stainless there.

The Armada had resonators ahead of the muffler in place of the secondary cats. They look very similar.
I haven't looked at the dimensions of those yet.
Very busy lately, probably a Spring project.

PS: I wasn't able to get the muffler flat to the ground, it would only line up at an angle since the passenger cat was welded slightly off, which threw off the geometry at the rear slip flange. Luckily the muffler is an offset, if it was straight, it never would have fit by about 2". Didn't want to crack my manifolds!

* Dynomax 19443 in case someone is googling that #

AZhitman wrote: ↑

Tue Dec 24, 2019 11:16 am

Nice investigative work, Squee!

Not sure how I missed this one, but I went through that with our 97 Pathy... no corrosion on the body but the grounds were almost completely nonexistent!

Glad you found the culprit.

Thanks AZH

The body/frame is shockingly nice for a Wisconsin vehicle. Those grounds were fried, it was the first thing I did and the X ran better immediately. The brass ground tabs on the cam cover had literally etched a groove into the aluminum that was filled with corrosion, and the bolts were so rotten I thought they were going to snap. Still need to buy one of those induction bolt heaters.

Thanks since I use the X for my LA to SF runs i need quiet i will go with something more at stock do not need the extra 5 ponies. Glad i asked and appreciated the response.