ecu grounding

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jefferson
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Location: Parkville, Mo.

ecu grounding

Post by jefferson »

Just a little tip I got from a motorcycle forum that would possibly help our cars. It involves splicing into the ground for the ecu and running a dedicated ground back to the battery. One way to check if this could be of benefit is if there is voltage on that ground while running at an idle and also while revving. Benefits can be barely noticeable to dramatic. The older the vehicle the more resistance builds up in the loom and the ecu can pay the price in it's ability to function optimally. A little bit more involved than a grounding mod, but well worth the effort.
91 Black SS 5spd. Edm lights, wrx gauges in dash, 45 degree airbox, cryoed drilled and slotted brakes. Invidia divorced downpipe with custom stainless exhaust. To be installed, aluminum a-arms, manual belts, awic.
jefferson
Third Gear
Posts: 750
Joined: Sat Dec 16, 2006 4:41 am
Location: Parkville, Mo.

Re: ecu grounding

Post by jefferson »

Just as an aside to this. I ran a 14ga ground from the battery to the pivot bolt on the alternator and then another from the pivot bolt to the intake manifold. I'm getting much better charging now and the needle is steady instead of jumping around. I feel the car is running smoother and pulling better, but those things can be subjective. Either way it was well worth it for the charging alone.
91 Black SS 5spd. Edm lights, wrx gauges in dash, 45 degree airbox, cryoed drilled and slotted brakes. Invidia divorced downpipe with custom stainless exhaust. To be installed, aluminum a-arms, manual belts, awic.
Legacy777
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Re: ecu grounding

Post by Legacy777 »

Just to note, the ECU grounds itself to a point on the back side of the driver's side intake manifold. Alternatively, you can run a dedicated ground from that spot to the battery if your existing grounds are ok.


Good tip!
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
jefferson
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Posts: 750
Joined: Sat Dec 16, 2006 4:41 am
Location: Parkville, Mo.

Re: ecu grounding

Post by jefferson »

I though about going to that spot on the manifold, but it was so easy going to the empty bolt hole on the passenger side front of the manifold. Last time I got to the ground point on the manifold it was kind of a pain if I remember correctly.
91 Black SS 5spd. Edm lights, wrx gauges in dash, 45 degree airbox, cryoed drilled and slotted brakes. Invidia divorced downpipe with custom stainless exhaust. To be installed, aluminum a-arms, manual belts, awic.
damnsubi
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Re: ecu grounding

Post by damnsubi »

i looked on my 91 and couldn't find a ground wire on the back side of the driver's side ecu, maybe someone moved it
Legacy777
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Re: ecu grounding

Post by Legacy777 »

The ECU is grounded through the wiring in the connectors going to the ECU. There is no additional wiring going to the external part of the ECU.

The comment above was in reference to the intake manifold.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
85hpp
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Re: ecu grounding

Post by 85hpp »

This is good stuff, extra grounds can definitely fix/improve things on an older car. Subaru's might not have this problem but putting dedicated fat ground wires to the headlamps on my old Ford gave me much more light output :D
Pete - '94 Legacy 2wd/auto - Mobile nightclub in progress
- '02 Legacy Outback Sedan Limited - heated leather seats, sunroof, shiny paint, cherry condition - all things new to me :)
- 2006 Honda Reflex 250cc
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