Fixing a jacked up car, AKA – the right way to wire a standalone, Part 1

This will be a multi part series as I just received the car yesterday and I am sure I will have more surprises along the way.

The enthusiast that dropped it off to me complained of poor drivability, inability to stay running when warm, excessively hard shifts, as well as just a lack of trust in the shop that performed the work initially.

Before I even got to drive the car, I started a basic inspection.  First thing I wanted to see was how the standalone (an AEM V1) was wired to the stock ECU.


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In all fairness, those are disconnected because I started trying to straighten up the wiring.  Before, it was a mess, no zip ties on common bunches, etc.  I decided after I first started that I needed to start documenting everything I found

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Yes, that is electrical tape insulating the connections to the stock +12v supply.

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Here, we have a resistor just kind of hanging out.  It is supplying resistance to the crank sensor, but I’ve never had to do that when running a standalone in conjunction with the stock ECU – in fact, the resistors need removed from the standalone in order to make it work right.  Further inspection is required.  Either way, the resistor is not insulated and is just chillin.

Ok, so, you’re thinking, this isn’t all too bad.  Well, the shop did not wire in intake air temp whatsoever.  Who knows why, but I knew that one of the first things I would need to do would be to add intake air temp.  The enthusiast who owns the car had already purchased and started to install, but became overwhelmed with the wiring.  Just when I’m thinking this isn’t all that bad, I decide to snip the ziptie holding the AEM in place under the drivers side of the dash.

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At this exact moment, my heart skipped a beat.  What I thought was initially going to be a quick and easy fix just became a mini-nightmare.  I decide I’m in it this far, lets inspect a little further.

I detached the mainboard from the case via the 3 screws underneath.  Yes, I said 3.  One was missing, as there is clearly supposed to be 4.

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Ok, so, this is scary, but what comes next almost made me cry.

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Speechless.  I had to sit down for a solid 5 minutes and decide which way to attack this.  I don’t like spending other peoples money, but this is so not right, on a ridiculous level.

Alright, so, first thing I had to do was to order the correct ECU plugs. This is an EVO9 plug n play AEM V1 30-1320.  For those that don’t understand that part in an IS300, well, we can use pretty much any AEM (I personally used to use the 30-6101 Supra box).  To make this right, I ordered the correct ECU plugs and pins from a cool EVO-centric website  I even ordered more pins than I would need, but you can see the order below.

Fullscreen capture 442015 53153 PM-001

Just $48 (plus shipping) to avoid wiring this the worst way possible.

Just a quick list of other things I found that need to be changed:

1) MAF clamp – since the stock MAF is kept in the loop on these dual ECU setups, it needs to be clamped.  I’ve had good luck with a simple 4.2v diode.  This could be the explanation for the hard shifts, as the stock ECU uses MAF signal for part of its shift algorithm.

2) Intake air temp – this will be added.  I’m not sure how anyone expected a speed density setup to work without a proper air temp sensor wired in.

3) He was told it was running 18 psi, but it appears the wastegate spring is 12 psi.  There is a connection for a boost control solenoid, but there isn’t one installed anywhere on the car.

4) The GM MAP sensor appears to be a knockoff.  I’ve experienced these and haven’t had good luck with them at all.  Will require further inspection.

There may be more and I will update this as time comes.

Part 2 will be published once I’ve started cleaning up the AEM to be installed correctly.




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