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Ground with Ignition off from AEM FIC piggy back tuner

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Old 03-27-2014, 07:52 PM   #1
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Ground with Ignition off from AEM FIC piggy back tuner

Im experiencing an erratic ground when I have the FIC connected and turn the truck off. It doesnt come on immediately, usually about 10-30min after turning off the truck and it causes the air bag light in the dash to come on (SRS warning light is powered off the 7.5A ECU-B fuse). Its also very inconsistent, sometimes not showing up for days. It usually takes about 5-10 hours to drain the battery. If I disconnect the ignition power source from the FIC and then reconnect it, the ground goes away and never returns until I start and subsequently shut off my truck.

Ive swapped out the unit with a good one and experienced the same issue. Ive double and triple checked all the wiring (wire diagram attached in zip folder). Two power ground leads from the FIC are connected IAW instructions, one connected to E01 and one connected to E02. Signal ground connected to E1 (shielded ground for sensors). 12V power wire connected to IGSW (ignition 12v source).

AEM FIC forums are down and AEM FIC phone support sucks (they keep telling me Im wired to the "constant 12V" vice "ignition 12V" source).

Here is something Ive found in the Scion forums where the FIC keeps some sensors engaged when the ignition is shut off. I dont know how this will apply to me but I doubt this is the issue as Im pretty much the only 1st gen Tacoma experiencing it:

http://www.scionlife.com/forums/showthread.php?t=210269
Attached Files
File Type: zip 5vz Wire Diagram.zip (90.5 KB, 2 views)
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Old 03-28-2014, 03:40 AM   #2
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I'll look it over today and see if I find anything.
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Old 03-28-2014, 09:24 AM   #3
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After reviewing the schematic it doesn't make sense? How did you come to the conclusion that there is a ground causing the issue? I'm thinking maybe we need to check power on the IGSW wire after you turn your truck off. If there is 12V there it's still on. If there is not 12V there we need to check each wire to see if any of the connected wires have 12V. Something has to be drawing the power while the truck is shut off.

Did you double check the wiring to make sure all wires are correctly spliced in the FIC wiring? There is a chance we spliced one wire just one pin off.

If you totally disconnect the FIC wiring and the AEM and your battery is not draining then 100% the problem has to be in the FIC wiring.
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Old 03-28-2014, 10:32 AM   #4
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Quote:
Originally Posted by Rons01TRD View Post
After reviewing the schematic it doesn't make sense? How did you come to the conclusion that there is a ground causing the issue? I'm thinking maybe we need to check power on the IGSW wire after you turn your truck off. If there is 12V there it's still on. If there is not 12V there we need to check each wire to see if any of the connected wires have 12V. Something has to be drawing the power while the truck is shut off.

Did you double check the wiring to make sure all wires are correctly spliced in the FIC wiring? There is a chance we spliced one wire just one pin off.

If you totally disconnect the FIC wiring and the AEM and your battery is not draining then 100% the problem has to be in the FIC wiring.
So when I disconnect the 24pin connector from the FIC, the dash light briefly flickers but stays on. When I disconnect the 22pin from the FIC, it goes away. So I troubleshot further and started disconnecting the terminals from the ECU. The ground only goes away when I disconnect the E5 terminal which only has the ignition power wire spliced in (no other wire connected to the FIC).

Here's the kicker. When I checked for voltage on the ignition power wire, I got nothing. When I reconnect the FIC, the ground doesnt come back until after starting the truck again. Just like in the Scion thread, something isnt turning off when I shut the truck off. Since Im pretty much the only Tacoma with this issue, I think it might be a faulty sensor that fails to de-energize... (like the Scion issue...).

My next step is to leave the 24pin connector in the FIC and test the 22 pin for voltage to see what readings I get. I dont know how to test the pins on the 24pin connector without disconnecting it (and thus clearing the ground).

I dont have a clue what the ECU-B fuse fits into all of this but I have a feeling its important.
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Old 03-28-2014, 12:23 PM   #5
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Ron, we may have to splice some test points into each wire to measure where the voltage leak is.
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