AEM EMS loses connection every 30-40 seconds - Dodge SRT Forum
 
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post #1 of 6 (permalink) Old 06-10-2016, 01:25 PM Thread Starter
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AEM EMS loses connection every 30-40 seconds

I had a AEM credentialed shop install and tune my EMS. Everything was going great, car started up first time with correct base file, after a few tweeks the tuner was driving around the parking lot, then it went on the dyno. About half way through tuning the car died. It would not start up and while cranking almost tried to start the engine backwards (you could hear the flywheel bang off of the starter). After a while it was determined that the crank signal was jacked up, it had a lot of noise. The crank signal was re-wired and the shop told me that the AEM might of fried that part of the wiring. Got the car running again, but every 30-40 seconds the engine stumbled hard and the connection to the laptop would disconnect and quickly reconnect. The shop was not able to explain why, aside from saying the AEM EMS was bad. When the stock PCM was hooked back up the car did not stumble at all. Has anyone encountered this problem? I've researched and most issues appear to be with the coil driver (happened to two people I actually know as well), but I have yet to see this issue logged anywhere.

It's a V1 unit, AEM UEGO wired in, second pump controlled by the A/C relay pin since I took the A/C out, and wired with the AEM boost solenoid. The shop did extend the harness from the AEM to the stock PCM so it could be mounted in a different location (pretty much where some of the CAI's run), but the shop said that wasn't the issue.

Any suggestions on what to check? The shop informed me that AEM has zero support for this unit now, so not even sure where I would have it checked out at. The unit was brand new in box when I handed it to them.

Thank you for your time.

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post #2 of 6 (permalink) Old 06-10-2016, 02:09 PM
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I had a AEM credentialed shop install and tune my EMS. Everything was going great, car started up first time with correct base file, after a few tweeks the tuner was driving around the parking lot, then it went on the dyno.

About half way through tuning the car died. It would not start up and while cranking almost tried to start the engine backwards (you could hear the flywheel bang off of the starter).

This doens't make any sense. The starter is an electromechanical device. It only spins one way and that is determined by its design. The EMS only provides the starter solenoid (relay in essence) input to the starter.

After a while it was determined that the crank signal was jacked up, it had a lot of noise. The crank signal was re-wired and the shop told me that the AEM might of fried that part of the wiring. Got the car running again, but every 30-40 seconds the engine stumbled hard and the connection to the laptop would disconnect and quickly reconnect. The shop was not able to explain why, aside from saying the AEM EMS was bad. When the stock PCM was hooked back up the car did not stumble at all. Has anyone encountered this problem? I've researched and most issues appear to be with the coil driver (happened to two people I actually know as well), but I have yet to see this issue logged anywhere.

It's a V1 unit, AEM UEGO wired in, second pump controlled by the A/C relay pin since I took the A/C out, and wired with the AEM boost solenoid. The shop did extend the harness from the AEM to the stock PCM so it could be mounted in a different location (pretty much where some of the CAI's run), but the shop said that wasn't the issue.

Any suggestions on what to check? The shop informed me that AEM has zero support for this unit now, so not even sure where I would have it checked out at. The unit was brand new in box when I handed it to them.

Thank you for your time.
Yes support has discontinued for the EMS.

Here are some third party options that may be able to help: AEM Performance Electronics Support - Series 1 EMS Technical Support Ending | AEM I am guessing that AEM sold the stock parts, manuals, and schematics to the vendors listed on the bottom of that page.

It is odd that an experienced tuner can not capture what is happening in the logs unless the logs are clean. If that is the case then something within the box may be bad, or there is the possibility of a faulty solder joint that is causing intermittent issues.

A stumble due to coil driver failure can easily be tested by switching to another coil bank within the EMS (it can run up to 10 cylinders IIRC). You will have to switch wires around, and change the coil config within the tune.

Now if the EMS is disconnecting and stumbling at the same time I'd lean more towards a faulty power or ground connection somewhere. Logs would show this.

I am not a fan of spliced wiring harnesses as they introduce an entry point for failure. If the harness was not properly stripped, wrapped, soldered, and heat shrunk with automotive grade tubing (with sealant goo inside) it is VERY possible that the extended harness is bad. Saying it is good and actually end to end testing it while moving/shaking it to simulate vibrations and such are two very different things. I am doubting that they did test it thoroughly.

I don't think the tuner you are dealing with is an expert with the EMS or else they would be able to exactly identify what is wrong. Sure they may be a great tuner, but the EMS is a very complex box that takes a "special" understanding on how the box functions. The EMS literally logs EVERYTHING, and all it takes is a educated guess on where to start first such as everything power related (batt voltage...etc). Do not rely on logs captured with a laptop! You must log internally to capture hiccups that cause the laptop to disconnect. Internal logs kinda suck to download via laptop, but are the best way to troubleshoot the EMS.

It would be nice if you knew someone close that you could swap boxes with and see if indeed your box is bad, or if it is external to the EMS. I could look at your box in my car in a limited setting since my car isn't 100% street legal at this moment and I'll be limited to around the neighborhood driving. Not the most ideal option, but I figure it is worth the offer.

Last edited by atroph; 06-10-2016 at 02:14 PM.
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post #3 of 6 (permalink) Old 06-10-2016, 02:24 PM Thread Starter
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Thanks for the reply.

The flywheel was banging off of the starter, as in the ignition timing was so far off that it was rotating the engine backwards, not the starter itself.

Pretty sure the issue is not the coil driver, as the symptoms don't match up.

I watched them extend the harness, they did it to my liking. However I'm not sure they thoroughly tested it once the issue occurred. The odd part was that the car was running great with everything installed for hours before it crapped out.

I will inquire about the internal logging.

I appreciate the offer for checking out my box (hehe), but I live in Seattle. If I was to send it out I would probably just send it to streetlightz.

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post #4 of 6 (permalink) Old 06-20-2016, 11:23 AM
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The portion of the harness that was extended is the jumper for the stock ECU from the AEM box, not the engine harness connections to the AEM EMS itself.

As for logging, internally to the EMS the box is shutting off then restarting. It was the internal logs that told me why the car was stumbling and dieing for no apparent reason every 30-40 seconds. The reason is unknown. I also leaned towards power and ground circuits specifically the ASD relay built into the car. Bypassing this circuit with a manual switching relay the EMS still powers down and restarts for unknown reasons. My best guess was an internal short in the EMS that fried the crank position wiring/sensor while the car was on the dyno. This is something I've never seen before but it's not entirely impossible. I also wish I had another car with an AEM ems box I could swap on and try.

I don't think it has anything to do with coil drivers, it was am immediate thought but that's it. Never a diagnosis of any kind.

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post #5 of 6 (permalink) Old 06-20-2016, 11:52 AM
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"They" won't tell you but the old EMS units have been known to just power off at the most inconvenient times.
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post #6 of 6 (permalink) Old 06-21-2016, 08:48 AM
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The portion of the harness that was extended is the jumper for the stock ECU from the AEM box, not the engine harness connections to the AEM EMS itself.

As for logging, internally to the EMS the box is shutting off then restarting. It was the internal logs that told me why the car was stumbling and dieing for no apparent reason every 30-40 seconds. The reason is unknown. I also leaned towards power and ground circuits specifically the ASD relay built into the car. Bypassing this circuit with a manual switching relay the EMS still powers down and restarts for unknown reasons. My best guess was an internal short in the EMS that fried the crank position wiring/sensor while the car was on the dyno. This is something I've never seen before but it's not entirely impossible. I also wish I had another car with an AEM ems box I could swap on and try.

I don't think it has anything to do with coil drivers, it was am immediate thought but that's it. Never a diagnosis of any kind.
Hmmmm..... I am guessing you are the tuner? It always makes things a little more clear hearing the info directly from the source

It is very possible that something within the power supply circuitry is bad/intermittent causing the random reboot and unreliable CKPS. Probably related to either heat or vibration that has caused a faulty run, or an aged discrete component like a capacitor or voltage regulator.

My best recommendation would be to send it to the repair facility listed on the AEM site.

FFChips and StreetLightz.

FFChips' site appears to be down atm, but streetlightz is here: https://streetlightz.3dcartstores.co...s_p_18007.html

Best of luck!

Last edited by atroph; 06-21-2016 at 08:55 AM.
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