Won't connect/boot without hard reset. | AEM
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FauxZ
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Last seen: 4 years 6 months ago
Joined: 03/05/2016 - 22:55
Won't connect/boot without hard reset.

V2, 2JZGTE in a MKIII Supra.  I had the car up and running for a few weeks, just doing leak checks and idle maps, never even put it in gear.  No problems.  I left for work, and the car sat for 45 days, on the charger.  Since then, I've started it a couple of times, and it moved far enough to get turned around in the driveway.  However, I now have an issue were the EMS won't come online unless I pull the battery for a few seconds.  Pumps won't prime, it won't connect to laptop, nothing.  If I cycle the battery, it comes online fine, maps are there, voltage is good, but as soon as I shut it off, it won't come back until I cycle power again. 

Switched 12v, battery, and EFI 12v all seem to function normally.  I also removed the EFI relay to (maybe?) test for a stuck relay, but it doesn't seem to matter.  Suggestions? 

 

Z

 

AEM_NS
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Last seen: 2 hours 8 min ago
Joined: 06/06/2014 - 09:31
Sounds like the EMS isn't

Sounds like the EMS isn't fully powering down after you key off.  Complete power down only occurs when you completely remove all power by disconnecting the battery.  This could be a wiring problem.  You might have something like a lowside output connected to a device that has permanent 12v power present instead of switched 12v power.  This will create a condition where 12v power is back fed into the EMS which keeps it from fully powering down.  I'd suggest disconnecting all I/O (coils, injectors, sensors, all lowsides, etc) to see if the EMS will key on/off correctly with nothing but power and ground connected.  Try that and report back.

FauxZ
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Last seen: 4 years 6 months ago
Joined: 03/05/2016 - 22:55
Will do.  Thank you.   

Will do.  Thank you. 

 

FauxZ
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Last seen: 4 years 6 months ago
Joined: 03/05/2016 - 22:55
Found the issue, it's the

Found the issue, it's the coil off the fuel pump relay.  I have it piggy backed off the 12v feed for the pumps, which is a bad idea anyways.  If I pull the fuse for those, it works fine.  I'll be rewiring the relay to switched power, like I should have anyways.  

Thank you for the help.  

AEM_NS
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Last seen: 2 hours 8 min ago
Joined: 06/06/2014 - 09:31
Sure thing.  Glad you found

Sure thing.  Glad you found it.