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Subject: Using the Aftermarket Utilization connector (X14) of the MBEC for Accessories for GMT-900 trucks
Topic Description: The MBEC is located underneath the drivers side dash and contains the Aftermarket Utilization connector that can be used to power added accessories. The connection block has a 15 amp battery feed, 30 amp battery feed, 10 amp Run/Crank feed, 300 milliamp Retained Accessories Power (RAP) trigger, and ground. The two battery feeds (always hot) and Run/Crank feed can be wired directly to accessories that draw less than the stated amps. The retained power accessories pin can be used to trigger a relay or amp remote turn on. It cannot be used to directly power a device. A diode should be used with relays. You can push small crimp on terminals from the auto parts store over the pins, but the guide below will cover the correct way to use the connection block with the proper connectors.

*Warning* - Do not use these instruction on "Hybrid" model trucks. See GM UI Bulletin 89c for instructions.
https://www.gmupfitter.com/files/media/photo/808/UI Bulletin 89c_7_2017.pdf

Requirements:
*Skill Level: Basic 12V wiring knowledge required
*Time: 2 hours or less
*Special Tools: Multimeter/test light, wire stripper/crimper and/or soldering iron

The following parts are needed:
*GM Connector P/N 20791502
*Automotive Connectors FMALE 280 SERIES TIN CBL RNG P/N 15304711-L

The following parts are optional and depend on the accessories being installed:
*5 Pin SPDT relay and harness for high amp accessories
*Diode for use with a relay GM P/N 12112422 or equivalent
*heat shrink tubing or electrical tape
*automotive copper wire
*butt splices or soldering iron or similar connectors

I recommend that you order several extra pins.

Step-by-Step Instructions:

Locate the MBEC under the drivers side of the dash. Gently remove the cover by wiggling the edges and pulling it back. There is a plastic prong panel clip in the center that you don't want to damage.


The X14 junction block is the last connector on the left (my hand is holding my accessories wires going to it).


Here is a shot of the X14 connector (P/N 20791502) with the pins labeled according to my table below.


The table below shows what each pin can be used for. Accessories drawing more than 30 amps should be wired to the battery or under hood fuse block posts. A relay should be used with the RAP pin for anything other than something like an amp remote turn on.



If you want the accessories to stay on with RAP (like your radio), you will need to purchase a 12V automotive relay as pictured below. The harness is not required, but they are not very expensive and make it safer/easier to remove or install the relay. For more information on wiring a relay, please visit http://www.the12volt.com/relays/relays.asp . The RAP (Pin 8) would be the trigger, the Battery Feed (Pin 2 or Pin 5) would be the 12V+ supply, ground to ground, and finally the output pin of the relay to your accessory. If you want Run/Crank to be the trigger (and need more than 10A), you could substitute Pin 7 for Pin 8. A diode should be installed across the coil of the solenoid. One end of the diode should be connected to the positive terminal of the coil and the other end of the diode should be connected to ground. For GM P/N 12112422, the striped end of the diode connects to the positive relay pin.


Even though I have checked and documented the pins for ground and 12V+ on my 2012, I highly recommend that you do the same before connecting any accessory to the MBEC in your truck. You can check the pins with a circuit tester (pictured below) or multi-meter set to 12V DC. I used both while investigating. You can check by confirming that the certain pins are always hot and that the others are hot only when the key is in the proper position. Checking will take just a few minutes, but could save your electronics if something is different on your particular model/year.


Conclusion: You can use the X14 Aftermarket Utilization connector in the MBEC to power accessories in the cab. The connector gives you the flexibility to have your accessories always powered, powered with RAP, or powered with Run/Crank. You can power extra 12v outlets wired to the ignition (useful for GPS) or switches that are wired to relays outside of the cab for light bars and other accessories easily with this method. One way diodes are recommended by GM when using relays. Failure to use a diode could result in module damage. Official GM Upfitter Electrical Manuals were used as the reference for creating this guide.
 

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I am installing heated seats and was planning on using the MBEC X14 connector and I have a question.

I see the 60A fuse for the MBEC panel but nothing else under the hood. Are the 30A and 15A in the MBEC fused under the hood somewhere or do I need to fuse the line I am running for the seat heaters?

Thanks,

Bob
 

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So if I wanted to add a USB charging port and a lighted switch, I would have the RAP control the relay and the 15 AMP be the power source, do I need a diode? If so, where would I install it, coming from the RAP terminal going to the relay?

Thanks,
Karl
 

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Thank you Rebelman!!
Used this to wire up power windows in my 2011 1500. No chance I would have figured this one out without your post.
Can't imagine the pennies Chevy is saving by building these without power windows and locks...but they're still doing it!
 

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2010 GMC SIerra All Terrain C.C. 4x4 5.3
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Wow...just came across this. I knew there was power in the MBEC...but I was not aware that you could buy a nice factory plug to use to connect to that section.
 

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Cut it out of a donor vehicle from a pick and pull yard. It can be a similar connector in the same box and you may have to modify it (shave a bit off) and re-pin it. If you get lucky you may find a donor that has the exact one. That is how I did mine for aftermarket seat heater.
 

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Yes ... easily found and dirt cheap. I went to my local junk yard, searched the Chevrolet/GMC truck isles and grabbed about a half dozen connectors from a few trucks. I brought along my cable cutters and made sure that I left about 6" of wires on the connectors.

When I got home I took one of them, removed all the wires except the ones I needed for my project & popped it in the truck. If my memory serves me correctly I think that I had to cut or shave a key way on the side of one of them to get it to fit into the MBEC ... maybe they were keyed to a particular spot?

Anyways it worked perfectly and only cost a buck or two!
 

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What I did was pull the red locking tab and inserted two additional pins for the 15A and the 30A connections to run a power port bar and heated seats.

I have two pins left over from when I tapped the MBEC panel on my truck.

If you PM me your address I will mail them to you.

Bob
 

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2010 GMC SIerra All Terrain C.C. 4x4 5.3
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2001 GMC Sierra 2500HD CCSB
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I actually bought that one nealinator. It only came with 1 or 2 pins, and very small wiring. So it's not that useful unless you go source the terminals elsewhere, which I did.

Pretty sure I bought the correct terminals on arrow.com. All together with shipping the bare pins and the connector price is probably similar as just buying that more expensive one with all the pins and decent sized wiring pigtails already on it.

I had intended to swap out my boss's extra accessory fuse block to be powered with this, but never got around to it. Works fine as is...
 

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