Do I have AEM EMS Problems - Page 2 - Dodge SRT Forum
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post #16 of 25 (permalink) Old 07-21-2012, 10:52 PM Thread Starter
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Yeah I will see if I can get help from AEM directly, or on the forums, and if I can get it to work, I will post up what was required to do so.

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post #17 of 25 (permalink) Old 07-22-2012, 11:28 AM
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You will only see stat sync when the car is cranking.

First I would download the Cal from the ems and email it to yourself.

Then try turning over the engine and see if stat sync ever changes to on. without stat sync you will never get spark and injector pulses.

if you do not get state sync then you will need to log can and crank signals.

or try the easy route and load the srt4 base Cal. you will need to do a fuel rescale matching your current fuel pressure and injector size. there is a wizard for that which is pretty easy.

either way no stat sync = no start.
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post #18 of 25 (permalink) Old 07-22-2012, 12:58 PM Thread Starter
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Well, I think I've got to find the problem that is apparently one step before all that. That is to say that this car does not crank at all. So, no crank, means it is definitely not going to even get to the stat sync part.

I've got to figure out why it won't even crank. I'd be a little happier if it would at least crank.

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post #19 of 25 (permalink) Old 05-15-2014, 08:41 PM
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My aem will not hold battery voltage ....it slowly declines until it stalls out . But if I plug in just the stock pcm car holds voltage fine. Also I already sent it in for inspection and it came back good. Installed it again and the same problem.

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post #20 of 25 (permalink) Old 05-16-2014, 12:20 PM
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What do you mean by battery voltage? Is the car running or not? What are you using to measure the voltage? The EMS or a voltmeter?

I would say that if you are getting not volts while the car is running then there might be an issue with the field wire going to the alternator. IIRC the field is controlled by the stock PCM and passed through the EMS to the alternator. I could be wrong.

Please be specific about your problem.
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post #21 of 25 (permalink) Old 05-16-2014, 04:44 PM
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What do you mean by battery voltage? Is the car running or not? What are you using to measure the voltage? The EMS or a voltmeter?

I would say that if you are getting not volts while the car is running then there might be an issue with the field wire going to the alternator. IIRC the field is controlled by the stock PCM and passed through the EMS to the alternator. I could be wrong.

Please be specific about your problem.
The car starts and runs and drives with aem ems installed but doesn't hold voltage. The battery slowly just depletes and the battery light is on. We replaced the alternator and same result . But if we take the ems off the car and run just the stock pcm the car maintains a steady voltage as it is suppose to

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post #22 of 25 (permalink) Old 05-16-2014, 07:30 PM
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Ahh OK. I'll look at the diagrams and post back. IIRC the stock pcm feeds the alternator field is controlled by the stock pcm and passes through the ems untouched.
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post #23 of 25 (permalink) Old 05-16-2014, 10:57 PM
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Ok just looked at the manual.

There is a piggy back harness going to your stock PCM if you have the original Series 1 PnP EMS.

Here is a simple picture I created for a recent project:



Here is the link to the manual that I am referencing (from JSC Speed):
http://www.jscspeed.com/media/aem_srt4_ems.pdf

Now looking at page 14 of 18 you can see there there is an output to the field control on C4-14. Then the field control is routed to the alternator on C2-19 on page 13 of 18. What happens inside the EMS is unknown, but I think it is a direct shot from the factory PCM in to the EMS and then out to the alternator. I don't think that the EMS does anything to develop the field voltage to the alternator.

If it were me I'd check the piggy back harness and make sure that there is good continuity to the other side of the cable. I can do some testing if you need to see if there is any change to the field inside the EMS, but I doubt it.

Basically the wiring is like this:
Factory PCM C2-19 -- Interface Harness -- EMS C4-14 -- EMS C2-19 -- Alternator

HTH.

Last edited by atroph; 05-16-2014 at 10:59 PM.
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post #24 of 25 (permalink) Old 05-17-2014, 05:05 AM
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Ok just looked at the manual.

There is a piggy back harness going to your stock PCM if you have the original Series 1 PnP EMS.

Here is a simple picture I created for a recent project:



Here is the link to the manual that I am referencing (from JSC Speed):
http://www.jscspeed.com/media/aem_srt4_ems.pdf

Now looking at page 14 of 18 you can see there there is an output to the field control on C4-14. Then the field control is routed to the alternator on C2-19 on page 13 of 18. What happens inside the EMS is unknown, but I think it is a direct shot from the factory PCM in to the EMS and then out to the alternator. I don't think that the EMS does anything to develop the field voltage to the alternator.

If it were me I'd check the piggy back harness and make sure that there is good continuity to the other side of the cable. I can do some testing if you need to see if there is any change to the field inside the EMS, but I doubt it.

Basically the wiring is like this:
Factory PCM C2-19 -- Interface Harness -- EMS C4-14 -- EMS C2-19 -- Alternator

HTH.
Awesome thanks I'm going to check it out and see . Yea if you got the time that would be cool to if you could test , I found a thread on here apparently several people have had the same issues

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post #25 of 25 (permalink) Old 05-17-2014, 01:54 PM
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Ok just checked. The wiring is correct as I posted it above, and indeed the EMS just passes the field voltage to the alternator.

Best way to test is to remove C2 from the stock PCM and the EMS. Test PIN 19 (second row down all by itself at the end) and stick the other lead of your DMM on C2 Pin 19 on the EMS. There should be less than 1 ohm of resistance. If not then you need to test the jumper harness by testing C2-19 (PCM side) to C4-14 (EMS Side). If that is good then test C4-14 to C2-19 on the EMS itself. That should read 0 ohms as well. IMO your problem is one of those things, or you have a bad signal ground on the other pin of the alternator. I don't think the ground is bad because it works with the stock PCM.

The EMS does nothing to the field signal from the stock PCM. It just comes in and goes right back out.

HTH
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