2000 Maxima - I just changed the head gaskets, got it back together and no start, no spark, solid security light and linking error to ecu. 50 miles to a nissan dealer. I have 12v to the injectors but no ground, I just checked spark last night and have none. I tried all three keys, will no battery for a month or two cause key security issues? I hate to drag it to Nissan and have them tell me I need a new ecu for a few thousand dollars. Does a security issue cause a linking issue?
Try this.
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Turn ignition switch on, (do not start engine), and wait five seconds.
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Turn ignition switch off.
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Repeat steps 1 and 2 twice, (total three times).
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Start engine.
Tester
You cant diagnose any of this until you get that security light sorted out. No telling what the ecu will do to prevent a start …each goes about it in a different fashion and probably on several levels.
Do not pass Go till you sort that out…thats for certain
Blackbird
Anything’s possible, but first suspect is you forgot to connect some connector or another in the process of changing out the head gaskets. You changed them yourself, right? That’s a big job, lots of stuff has to be taken apart, and it would be easy to miss a connection or two on re-assembly. So get out your flashlight and take a second look at all that. On my Corolla, right behind the intake manifold, in a very awkward place, nearly invisible to see with everything installed, there’s a spot where all the sensor and computer grounds attach to the chassis, and if that got missed this type of symptom could result. Likewise – again on my Corolla – there’s a removable electrical connector which attaches the engine ground to the chassis ground, likewise forgetting to connect that back up could cause this. I think something like that has happened on your Maxima.
One more thing, suggest to charge up the battery fully with a battery charger.
And think positive. At least you’ve proved the engine won’t start with no spark and no fuel … lol … 
Yes @GeorgeSanJose makes a good point… You removed several engine Grounds in order to do your job correctly… Leave one off or lose and Bingo… you gots problemos…
@ GeorgeSanJose - that would be ideal, I’ll go over everything again and let you know whether I find something. If it’s not a connection, I suspect the ecu because of linking error, security issue and no check engine light with key on. also no tach movement while turning over. Thanks to all.
Another thing you might do is verify power is getting to each of the dash fuses while the ignition switch is ON using a test light probe or meter. Use the slits on top of the fuses to make the checks.
well cant find anything disconnected. All fuses are good and getting power. Guess I’ll pull the ecu to see if I can tell if it’s bad.
Without the proper testing equipment you will not be able to test anything on the ECU.
I presume that this does turn over. In that case I would check to see that you have power to the Crank sensor. If the crank sensor is not working the ECU has no idea that the engine is turning over…hence it sends no signal to the coil/ coils.
I’m not sure but this may also have a cam sensor.
Yosemite
Since the fuses are getting power you now need to verify power is getting to the ECU. There very well could be a relay used to provide power to it and that is where the trouble is at.
After such major surgery… Your suspect list is fairly large… @Yosemite is dead right about you being able to ascertain the status of the ECU by looking at it…Trust us on that one… Ive stared like a fool at many a green circuit board hoping to see something black or blown…never that easy.
If I were you…I would go over all my grounds… I would also disconnect…and reconnect any and all engine harness plugs AND I would pay close attention to any wires or pins that are pushing out of those connections…sometimes a pin backs out of a plug when otherwise it looks like its fine.
You also need to understand why this isnt starting up… Got the timing correct? U sure? Check it…also when you try to start it…what doesn’t it have ? Fuel? Spark? Compression? Make sure you know what you have …and what you dont so you can narrow your focus a bit.
Blackbird
I’m assuming that this engine ran just prior to your doing a head gasket job.
I would then go over everything as @Honda Blackbird listed. If you only need spark there must be something in the ignition circuit that is the problem.
The only way that it would be the ECU…is if you did not pull the ground off the battery and you shorted something out as you were removing parts for the head gasket replacement.
Yosemite
There are some real good clues here that are talking to me as to where the problem lie’s. The injectors aren’t working because they ground through the ECU. The data port of the OBD2 connection is down most likely due to a lack of power to the reader. The CEL light isn’t working. The ignition isn’t working. All these things point to the ECU and I doubt that it is bad. I suspect there is a problem with the power to it. The OP has already stated that the dash fuses are good and getting power to them. There may be a relay involved with the power to the ECU or perhaps not. If there is a relay then the control lead to it needs to be checked also. Either way, I think the next best check is to verify power getting to the ECU. I don’t think there is a ground problem to the ECU but to see if there is, simply run a temporary ground jumper from the negative battery post to the ECU.
Cant argue with you there @Cougar … Methinks we are all on the right track. I would def go thru those grounds as well as every engine harness plug… Make sure they are seated…and something no one thinks about…ensure the pins didn’t backtrack inside those connectors. Most harnesses wont allow plugs to got in the wrong place…sometimes the harness leads YOU to where it is supposed to plug in… But sometimes…sometimes you can find a female plug that accepts the wrong male plug… Its a lot like life in that… Hahaha
Blackbird