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The mkiv Supra Owners Club

AEM question


dangerous brain

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Bit of a long running problem that has so far been intermittent. It basically just cuts out. Initially it only did it when hitting nasty potholes or bumps. It would then start again like nothing had happened. Once nearly two months ago it straight up cut out and wouldn't restart, I had it recovered and the next morning after a battery recharge it started straight away and has not had a re-occurence in nearly 2 months.

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Its probably the EPROM chip inside the AEM. If you pop open the side with the serial port on it, you'll see the chip. These can come slightly loose so will just need pressing on to ensure it's fitted properly. Usual signs of this is, pot holes etc knocking it loose - try tapping on the AEM itself. Seems to be a fairly common problem from searching the AEM forums.

 

Mine was doing the same, opened it up, clicked home the chip and have had no problems since :)

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Its probably the EPROM chip inside the AEM. If you pop open the side with the serial port on it, you'll see the chip. These can come slightly loose so will just need pressing on to ensure it's fitted properly. Usual signs of this is, pot holes etc knocking it loose - try tapping on the AEM itself. Seems to be a fairly common problem from searching the AEM forums.

 

Mine was doing the same, opened it up, clicked home the chip and have had no problems since :)

 

 

Oh well it isn't that then. Next stop the immobilisor I think.

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Its not that. For some reason my fuel pump is hard wired straight off the battery and comes on the instant the ignition is turned.

 

Grrrr one of my most hated "mods" of all time. Basically it sounds like someone has dicked it so that the AEM doesn't control the fuel pump, but it's run directly from the ignition.

That's fine unless you crash, where you would normally stall the engine and the fuel pump would cut out so it didn't pump fuel all over you. I would look into getting it reverted back to running right.

 

However, that doesn't get you back on the road for now. A starter for 10, if you turn the ignition on, can you connect with a laptop to the ECU? If not then it's a feed problem to the ECU. It should have 12 volts to pin 33A. You should also get 12 volts with the ignition on to pin 1A.

Also check that you have a good ground on pins 69B, 79B and 80B.

If those are all good, then check the output to the main relays from the ECU. That should be 12 volts from pin 24A. If not then solenoid coil 5 on the ECU is fecked.

If you're seeing 12 volts there, measure pin 33A. That should also be 12 volts. (Coming back from the main relay from what I can tell). If not then the main relay needs replacing.

 

If it's none of these, then it's quite likely that it's not down to the ECU. However that said, it's possible that one or more of the connectors in the plug have become worn over time and you're not getting full continuity across the pins. I've seen and heard about this a few times over last couple of years. Sorting them out is a right pain in the arse as you could well imagine.

 

Hope that helps mate, or if not removes a few variables from the mix!

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Ah that sounds like a feasible thing. Last time it did it I could get the car to cut out by moving the ECU. I will check that first thing in the AM thanks.

 

Think you answered your own problem there mate it can only be a loose wire or plug to the ecu if you moved it and it would cut out. at worst it could be a wire shorting out in the foot well some where near the ecu.

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Bry

 

Check pin at the ecu, IGSW - A1 has 12v when Ign is on. If it does then check pin M-Rel - A24 has 12v.

 

I expect Pin IGSW is loose on the connector.

 

Also chap as Tony said you really need to sort that fuel pump wiring. I didn't relise it had been done like that.

 

Ryan

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OK this is not good news. A component on the ecu circuit board is fried. I could smell a burning smell that I located to the ecu. When I opened the box up it was humming. I think its a capacitor. Its a small cylindrical item with one side flat, labelled up on the board as Q2 near the smaller connection. Now that in my book is not a good thing:( So first up can any electrical component repairer solder a new thingy on? And how do I find out what caused this issue in the first place?

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What completely repin the lot instead of say getting a second hand loom from jez. I expect Jez has loads left over from various manual swap outs.

 

I now have the part number of the transistor it is. Its a PN2222a and they retail at about £0.18 so hardly a bank breaker. Its connected to pin 22 on the smaller plug so that should narrow down the circuit I need to look at to find the fault.

EDIT

 

Ah well what would you know its the fuel pump ECU FPC pin and my fuel pump has been wired straight off the battery for some unkown reason.

 

I just found the resistors on ebay so if I can't get them in matlins I can get them online.

Edited by dangerous brain (see edit history)
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As the fuel pump isn't being controlled by the ECU, unless the ECU is real trick and know's if one of it's circuits is duff, the fact that the fuel control on the ecu isn't working won't stop your car from working.

For 18p, it's worth swapping it, but I would be surprised if it fixes it. I think it's going to be something else....

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