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Aem Smart Coil Wrx v3-v4 Wiring Issue


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I seem to be having a weird signal ground wiring issue with my new set of Aem smart coils. If i connect REF Ground to cylinder heads it seems to work just fine but if i leave it as is meaning wired to B137-24 car just doesnt start. Wiring itself is ok i checked. What could be the reason for this and can i use the expansion loom ground for ignition ground as i have other sensors grounded to that expansion loom ground.

Switched to these after having misfire issues from my old set of coils ls2 truck coils ds585(bought 2 sets new of coils  run great for 150-200miles and started misfiring above 25psi) 




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What coil pin are you referring to as "REF"?   Pin B?  

Is your B137-24 pin in position 16 in the link pinout? 

If both of those questions above are "yes" then it sounds like possibly a ground offset between engine and ecu.  These coils use TTL so quite low voltage switching point.  If you could back probe at a coil connector and measure voltage between pin A&B with just ign on, and also when cranking that will give us some clues.

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Yeah i am referring to Pin B



"Is your B137-24 pin in position 16 in the link pinout? "

Yeah its in 16 




Hmm i did measure the voltage between A&B  A&C A&D with ignition on. I dont remember the values but it was all basically same so i assumed grounding was ok. I will measure those again tomorrow and let u know the exact voltage. What would happen if i were to ground Pin B to somewhere else close to where ecu is grounded or maybe coil mount plates instead of bundling them together with Pin C. I have tried to find out some info regarding grounding issues some said  that could result in a blown coil in very rare circumstances (i mean grounding Pin B and C to cylinder head together). Pin D is directly connected to battery ground

BTW thanks again adam you are a life saver every time.


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Ok that should be fine.  I would expect those coils to be happy up with up to about 500mv offset.

So if it runs ok with B grounded to the cyl head then I would just leave it like that, it will be difficult to find why it is not happy with ECU ground without a scope etc.  I have seen many of those coils grounded that way working without drama although I do prefer to have that referencing ecu ground.      

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Modern OEM Subaru COP with internal ignitors work fine even at only 30psi boost.

585's are over-rated, far too many seem to get a hard on over them despite their massive and dangerous flaw of premature firing with too much dwell.


Your problem is a strange one. I've used IGN1A's on a few cars ( non-link ) and never had any issues with them. If you are not 100% sure the coil triggering system is working safely, I'd proceed with caution. Sparks firing at the wrong time, can cause big problems

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  • 3 weeks later...

@Stevieturbo @Adamw


After a month of changing everything like 3-4 times trying out new set of AEM coil packs twice spark plugs like 4-5 times and coil wires 4 times, another subaru mechanic told me that they have tried the same set of AEM coil packs on a race car and had the same problem.  So i decided to go back to original 2006 setup which immediately solved everything. I simply cant fathom why but apparently subaru dont like AEM coil packs. THANKS for everything again adam. You have been so helpful everytime. 

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