AEM Infinity is playing dead (due to fuel pump short that blows fuse 46?)
 

I'm hopeful my AEM Infinity isn't actually dead and that there is something that would explain it not getting power. But it was dead enough that I needed to have AAA tow me home today.

I drove ~25 minutes in 95+ degree weather today in MA with the AC on (first time I ever ran AC for any amount of time). Toward the end of my trip my Gaugeart gauge would blink "Engine Protect" (I set it up to do so if it ever tripped). It would "Engine Protect" when shifting from 1st into neutral and neutral into first.. so low speeds. Once I got driving there were no "Engine Protect" issues.

I got to my destination, ran inside to make a quick purchase, came out 2 minutes later and then the AEM Infinity wouldn't prime the fuel pump and my Gaugeart gauge wouldn't turn on (it gets power via AEM Infinity's AEMnet). SO I quickly reasoned that the AEM Infinity wasn't getting power. I'm thinking running the AC teased out some dormant electrical gremlin I didn't even know I had.

I called AEM a few times at the end of their day. I unplugged the 80-pin AEM wire harness connector for a few seconds like the first guy suggested, didn't help. Then I tried closing the loop on the "flash" wire of the AEM harness but when I turn ignition on the AEM infinity just isn't getting power. I called back a 3rd time and some tech with a shit attitude told me to verify if I was getting 12V on ignition to the Infinity and to verify ground. I asked for him to clarify how and he said with a multimeter (no shit buddy).. I still didn't get an answer on where to stick the multimeter probe (and it wasn't from lack of trying to get one). I have to believe I can only test that 12V is coming down the AEM wire harness (to pin 10 on the 80 pin connector). Similarly, I would imagine I need to verify ground to pins 33 and 43.

So long story short: I'm going to check all fuses.. and then call AEM back tomorrow (before I start probing the 80 pin connector on the AEM harness).

But figured I'd check with s2ki to see if anyone has any suggestions.

Stating the obvious, but: THIS SUCKS!

Did just find this on AEM's forums:
96.3 ChangeLog? | AEM

"A fix was added for the peripheral controller in all Infinity units which should make them more tolerant of battery voltage dropouts; this should allow the ECU to recover better (without needing to unplug the connectors) if the battery voltage drops too low while cranking the engine."

I had one instance in the past 3 years where my Infinity needed to get kicked hard. In that instance I disconnected the battery. But the fact that AEM is regularly telling customers to unplug the 80 pin connector from the Infinity to try to revive their ECU is pretty alarming. Nice they have a fix (maybe)... too bad it took this event for me to become aware of it.

Tested the various pins on the AEM harness. All GND pins (33, 43, 67) properly connected to ground. The +12V pins (10, 63, 68) weren't as successful: only pin 10 read +12V. Pins 63 and 68 provide "Main power" to the Infinity (and AEMnet). The AEM harness manual simply says "12 volt power from relay". Pin 63 reads 0.7V whereas pin 68 reads 0V.

SO now I'm left with a new question: where is this relay that feeds these 12V "main power" pins on the AEM harness? (I know close to nothing about relays.. but I'm increasingly hopeful the AEM Infinity isn't a brick and it is just some relay that needs fixing).

.

I had this same issue awhile back. If you are using the +12v off the aux plug on the infinity for any sensors/accessories and you have not fused that wire, if there is a short it will blow fuse 46 ACG S, which is in the fuse box under the hood. This fuse is what supplies power to the infinity via yellow/green tracer I believe.

Never did do that, until Charper732's reply (still not checked all of them but..)

Wasn't a problem with the relay on the AEM harness.

Thanks so much for your reply, yes fuse 46 ACG S was blown. And then I tried 3 more times to key on and have the fuel pump prime, gaugeart come on, etc. Fuse 46 ACG S blew all 3 times I tried. Before the last attempt I disconnected the AUX harness and AEMnet (which powers my gaugeart gauge) but it didn't change anything.

Seems like my AEM Infinity is nearly a brick. It does the key-on sequence but blows fuse 46 ACG S everytime. I'm RMA'ing it back to AEM for (hopeful) repair tomorrow.

But I'm very appreciative for the insight about the potential for that fuse to blow because I'd have gotten my AEM Infinity back only to fail immediately due to a blown fuse.

before sending it out, i would suggest you plug up your oem ecu and confirm the fuse is not blowing

I seriously doubt your infinity is a brick.
also, if you rewired your fuel pump for direct battery voltage and the fuse holder/wiring is not a high enough gauge, it will also cause the acg s fuse to blow.

Fuse 46 is connected to a lot of circuits. I would highly suggest you break out the wiring diagram and disconnect components and test wiring til you find it.

YES, the fuse blows with the OEM ecu also... but I already sent the Infinity out to AEM (not a big deal, would be nice for them to go over it just to verify all is working as expected).

SO now I have a new focus for chasing down this issue. I didn't rewire my fuel pump. Do you have any pointers for how to hunt for the source of the short? I'll try to find the relevant wiring diagram in the s2000 service manual... see how far I can get.

Thanks!

Based on the wiring diagrams in the manual my initial short list to try disconnecting was the fuel pump and the immobilizer. If I pull the 15A fuse for the fuel pump (closest to clutch under the dash) then fuse 46 does _not_ get blown.

So is it fair to assume that my electrical issue is localized to the fuel pump?

Try unplugging the fuel pump connector on top of the tank. If the fuse still blows after that then your main relay is probably damaged.