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Discussion Starter #1
Tried both methods to obtain error codes, no blinking lights at all, several time the car just died and would not start, after a period of time it would start again, replaced fuse relay, checked wiring to ptu, and cas, relocated and replaced ptu,. Do you think the ecu is done or it is not getting power? How would I check to see if the ecu is getting power? 95 300zx NA
 

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Doubtful it's an ECU power issue since the car does run. ECU error codes have fairly limited usefulness. I'd get a hold of the factory manual (on-line or buy a CD/DVD off eBay) and start working thru all the various sub-systems. Fuel line pressured correctly, is there spark, etc. The issue could be so many things or combinations of things.

This will help: http://twinturbo.net/nissan/300zx/forums/technical/view/922678/The-6-Ps-Proper-Preparation-Prevents-Piss-Poor-Performancegt.html

Did the car just stop running or was it parked a long time? What happened to it before this issue started?

It does seem strange you can't pull the ECU codes tho? The factory manual will have a wiring diagram of all the ECU connections - so using a digital voltage meter you'd be able to test for power at the harness connector.
 

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Discussion Starter #3
I had been driving the car daily, car runs great, I stop to fill up and no start, got under the hood and wiggled some wire around, then it starts,
couple weeks later car just dies going down the road, 5 min later starts , right up, this went on for a couple of months, all of a sudden it happens more often, replaced ptu, didn't help, ran a few more times, but now it won't start at all.
 

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Ok, doubt it's the ECU. More likely either the PTU harness (common issue) or maybe an issue with CAS or CAS harness. What exactly did you wiggle to fix? On passenger side of engine or drivers side?
 

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Discussion Starter #5
The first time it happened Wiggled the ign coil relay, which I replaced, didn't fix the problem, I did not replace the eng relay, I think I'll order one and replace that one too. I wiggled just about everything else, harness to cas and ptu, coil connectors, ground on the back of the engine. I am not sure that's what made it run each time. Each time I had to wait longer until the car started, the last time it was two days. I found the part in the FSM to check power to the ecu. Going to check that out, also going to go through the FSM and check ever thing else. Z1 Motorsports offers both the finished harness and the build your own, which would you recommend. I am not the best at soldering, guess I need to practice first.
The other thing I was going to mention is I went through a problem last year that I figured out was the battery shorting out on the hood, charged the battery several times before I figured it out, was thinking during that time something might of happened to the ecu.
 

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Since you have a later model Z, the PTU connector is better made. That Z1 solution is for older model year cars.

You can randomly replace things but that can get expensive ... follow the 6p link I posted earlier and system by system check everything out:
http://twinturbo.net/nissan/300zx/forums/technical/view/922678/The-6-Ps-Proper-Preparation-Prevents-Piss-Poor-Performancegt.html

Sadly there are so many things that could be causing this issue elimating the possibilities one by one is the best trouble shooting method. Other things it could be: bad fuel pump controller or failing fuel pump, ignition key switch failing, CAS is bad, failed main engine bay wiring harness, etc. The list is large but even just checking for spark (one cylinder on each side of engine) narrows down a few things - having spark means the CAS is good, ECU would be working, PTU and PTU wiring is probably fine.
 
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