February 20, 2018

Replaced the Cam sensors but she didn't idle right this morning. Starting to get really tired of borrowing the wife's car - she is too as she can't leave the house nowadays. I need to fix this ASAP. Starting to consider taking it to the stealership or trading it in for a new ride altogether...:crying:

February 21, 2018

Tried troubleshooting after work. I noticed that the voltage dropped quickly after idling and shutting off the engine, so I decided to do a full stress test of the electrical system.

What I did was I let the car idle for 3-4 mins, then I started turning on the accessories - High beams, A/C, Defroster, Hazards, Heated seats, blasting stereo on full bass, etc. Normal voltage while driving is usually 14.5v. With everything else running it dropped to 14.1v over 1-2 minutes. Then I turned off accessories and let the car idle so the battery could recover before shutting it off again.

After shutting it off, I switched the ignition to the "ON" position without starting the engine so I could run my code reader and I noticed it dropped from 12.7v all the way to 12.2v within about a minute. That didn't look right so I switched it off and used a DMM (voltmeter) to read the voltage off the battery directly and it was reading 12.13v, which is below spec.

After this discovery I ran the code reader and started/idled some more and got the same P1606 and P1606 pending with an additional P0300 and a random U1024 and P1421.

I checked my yellow top Optima battery's date of manufacture and reads 05/2013. The Optima website says battery life can range anywhere from 18 months all the way up to 4 years - depending on operating temperatures and whether or not the battery is properly maintained by the Alternator, etc:

https://www.optimabatteries.com/en-u...r-battery-last

I'm hoping the battery is the root cause - it seems like it would be time to replace it, but the symptoms don't add up. I really don't know anymore... I'm a former Computer Science/Electrical Engineering student, a full time web developer and consider myself proficient with tools and technology but I'm just out of ideas now and really tired of this. I don't want to get rid of my Z...

Any help would be appreciated at this point...:crying:

i have a friend that’s having the exact same problem and symptoms. i’m gonna keep researching the forums, but hopefully you find a solution brother.

Did either of you have any luck finding root cause? I'm having the same intermittent issue. Typically if I leave it alone overnight it just works. I fidgeted with the MAF and camshaft sensor connectors one time thinking that actually did something (the next morning) but I think it's just time (or ambient temperature) that solves it.

Mendoza keep us posted. My 2011 Nismo is having the same problem and its left me a few times with the P1606 code on the scanner.

I'll be dropping my Z off at the stealership soon and see if they can't figure out the problem. I have an extended warranty on it and this should be covered and once she's back I'll let you guys know what Nissan says

My Z had this happen again, anyone have any leads?

Hey everyone! I'm back and I can say with confidence that I've fixed my problem for good - the Z has been running fine for 3 weeks now (knock on wood). But before I share, I just want to note that my situation may be different from yours and as such my solution may not work for everyone, so definitely do your own research and get a second or third opinion.

TL : DR ; - It was the f**cking relays...

Since my last post I took my car to two different mechanics. The first shop didn't see anything wrong when I brought it in (I guess they ignored the P1606?), stated the car started up and drove fine and simply asked me to bring it back to them when the problem came back. The second shop stated that the only thing they could think of was to try and replace the entire EFI and engine room harnesses, then if that didn't work they would try replacing the ECM and hope for the best. However since parts & labor for those options weren't cost-effective solutions they said they didn't want to touch it and simply wished me the best of luck...

So I went to a local junk yard (Pick-U-Part in the San Fernando valley) and with the help of my brother who is an aspiring mechanic found a wrecked 2014 base model 370Z and salvaged the main two relays (VVEL and Window washer), an IPDM, a fuse box, a VVEL module and most of the Engine room harness. I spent days mapping out the harness by hand and studying the Factory Service Manual (specifically sections EC and PG).

In the end my process was to basically rip apart the car, revert the car back to stock in order to eliminate everything as a potential problem and meticulously put it back together. I basically removed the entire intake system (plenum, pipes, MAFs), reconstructed every electrical component near the battery compartment (fuse boxes, relay boxes, etc), replaced all the fuses (whether they were blown or not), cleaned up the wiring harnesses, checked for shorts to ground/power, brushed all the ground connections and then ran through all the major system calibrations (meaning initializing the VVEL, resetting the ECU, running the idle air volume learning process, etc). All this was probably overkill and I didn't find anything seriously wrong but I had to be absolutely sure.

Anyway that seemed to do the trick and I stress tested the s**t out of the Z wanting it to fail again. You name it I did it - I accelerated hard, sprayed water all over the engine bay and battery compartment, ran it cold, ran it hot, etc. The problem was fixed, but what was the root cause?

Well, my theory is that it was the relays all along. When I tried to swap them early in my troubleshooting I got a false positive and then ruled them out that thinking it had to be something else. The fact of the matter was that I didn't use the metal bracket that holds the relay box in place back when I first installed my Optima Yellow top battery because of wiring clearance issues. It is entirely possible that the relays were indeed faulty and that harsh driving conditions (such as a bumpy road) would shake up and trip the relays which would cut power to/from the VVEL module which explains the intermittent U1024 (CAN communication circuit). It wasn't the VVEL or the ECM like the manual says it is. I tried 3 different VVELs so I know it wasn't that and I wasn't getting codes for the ECM or anything else. It probably helped that the relays from the donor car were newer and made by a different manufacturer - My car is a 2009 and as a first-gen 370z it's understandable for parts to fail since the engineers probably haven't worked out all the bugs yet.

That's it! I hope you guys get some value out of this information and learn from my experience and mistakes. I also want to thank you guys for all your feedback and support - I was so close to giving up and selling my Z but right now am back to having good times!

Peace,

JMendoza
Mendoza Motorsports
Pacoima, CA

Vorex, yeah that was my experience as well. Typically the symptoms would go away overnight or after a day or so.

My understanding is that the capacitors and inductors inside the relays discharge and reset over time. Relays are basically made of light metals, plastic and ceramic so it makes sense that extreme temperatures would negatively affect them (mainly heat), but that's probably not the root cause.

My 370z is a 2009 and since it's a first generation model some parts are more likely to fail since the engineers don't have all the bugs worked out yet. If your car is newer, I would buy a brand new relay and replace the VVEL relay with that one, disconnect your car battery for a few minutes, plug it back in and drive modestly for a bit before pushing it harder.

Here's a video that you may find useful:
https://www.youtube.com/watch?v=DWmt6gorzUg

The Z's run hot - as I'm sure you're aware - and heat f**ks up parts over time. Look at all the plastic parts in the engine bay of some older cars. Connectors, wires and hoses become brittle and crack over time, so imagine what that does to relays and fuses which are basically plastic, ceramic and light duty metals!

If you still have warranty you should be okay, but mention the relays to the techs and ask what they think. Have them test the relays if they know how to.

Here's a video that you may find useful:
https://www.youtube.com/watch?v=DWmt6gorzUg

Update --

I replaced both relays in that VVEL box (since they are both the same, I said screw it). It's been 6 months and I haven't been stranded yet. Fingers crossed that this was the fix.

My Z is a 2010 -- I went with used relays off eBay from a 2015 leaf...

I'm intermittently experiencing similar issues but different Pcode.
Car goes to idle and has no throttle response. Getting a P1608.
Disconnecting battery clears the code and car seems to run fine until it happens again. Wondering if it's a similar relay issue.
Do you guys have part numbers for relays and maybe a link to instruction on replacing?
Thanks.

25230-7995A (replace dash with nothing or a space as every site lists it slightly differently.)

Thinking back I'm not sure if I ever pulled a battery lead but I certainly tried to clear the code with a scan tool and that rarely fixed it. It was always leave it sit overnight and it was fine again in the morning.

The pic attached shows the location of the box, it's item #4

Thanks for the info. I've never been able to clear the fault with tool. Always by removing batter lead.

Update to my issue: Had it happen again on way to work. This time removing battery lead would not clear the fault. Was showing P1609, P1089, P1092. Had it towed to dearlership and currently waiting on call to see what the damage is going to be.

I'm curious to hear the update on what the dealer found and what you decided to do

Vorex- was there any resolution with dealer?

My response was asking USNA94 about his dealer experience. I haven't had the issue since I replaced the relays.