Navigation Errors after upgrade to Sync3

Sync updater went flawlessly in about 45 minutes. Navigation works but prompts with a navigation fault message on every boot. DTC errors GPS open circuit. GPS fault. Consensus is that this is due to cheap GPS. I can’t retrofit the roof mount GPS on my 2015 Mustang so I’m stuck with this aftermarket crap. So I’d like to have a thread that lists GPS units that are known to fail.

I received this fault error with the following: Eightwood brand fakra-c GPS (Amazon), Bingfu brand fakra-c GPS (Amazon). Avoid them. Several reviews indicated success with the Eightwood brand, so I’m assuming either the product has changed or the reviewers were on an older version of Sync3 than 3.4 23188.

Based on a 2023 thread that is closed to comment, at least one anecdotal success story with Xtenzi. Just ordered Xtenzi brand, not to be confused with the blue pill. Each time it’s a full tear down of my dash on a 2015 Mustang!

If anyone has any other proven winners, please post them here. I’m worried that since I have the latest version of Sync3, some of the older reviews stating these products work may no longer be valid.

Also wondering about correct Apim Forscan settings for gps gyro and telematics unit? That could also throw an error if the Apim is looking for a device that isn’t present. I loaded the defaults for my Sync2 and programmed them onto the Sync3, then attempted to address the faulty settings one by one. Programming could still be an issue on my unit.

SYNC Region: NA

Navigation Variant: Non Nav

Manufacturer Year: Pre MY20

Install Type: Retrofit

Old SYNC Version: 2.3.17109

New SYNC Version: 3.4.23188

Do you have a error message, if so what is it?
navigation fault

Update Method: CyanLabs Syn3 Updater

Syn3 Updater Version: 3.4.23188

Syn3 Updater Documentation Read: yes

Syn3 Updater Log File

There was a really good one on amazon a while back that I was using… but it’s since disappeared. Wish I documented it better as I’d love to find the supplier of it to sell on my site. I’ll do some digging to see if I can find it again.

Went back through my search history on google from 3 years ago (creepy, Google, but thanks I guess :sweat_smile:) and realize I found the spec sheet for the product, I just couldn’t front the $ for their minimum SIXTY THOUSAND piece order requirement :sweat_smile:

Mitsumi GPA-CG2C5 GPS Antenna Spec Sheet

Or you could get an antenna off a 2018 that had Sync 3 and use a splitter like the one below that goes behind the glove box. This is the OEM way and the best way.

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Hi Bill- I had thought that the GPS on Mustangs was integrated into the Sirius fin on the roof? Which cars have a dash mount gps antenna suitable for this? A part number would be handy. I can see the part number for the splitter GB5T-19C181-AB with fakra-c connection but I don’t see a part number for an interior dash mount gps antenna. My car has a controller for the roof mount gps/sirius under the vented dash cover. These plugs would not fit it and I don’t think it’s compatible with sync3. The am/fm antenna is integrated into the rear window on the Mustang coupe. Not exactly universal parts LOL.

The SYNC 2 systems used a standalone GPS antenna/module that was “usually” mounted behind the IPC under the dash, Fusion, Explorer Flex and may others. The Sync 3 systems in most cases moved it to the roof antenna. Usually if you have Sirius than it will get the right signals from the roof mount but that is not always the case. You could buy the splitter and see if plugging it in will work. If it does not than you simply will not get a GPS signal. I believe that splitter was for either an Explorer or Expedition. Wire lengths are the only difference I believe.

There is an APIM AB setting that says where the antenna is mounted but I don’t think it matters much. If it does not work than getting a roof mount from a 2018 Mustang is probably necessary. There is a good chance your will work though. I looked up antennas for a 2015 and it included them up to 2020.

Personally, I have found all aftermarket antenna to be garbage but they do work for a lot of people.

I’m still not sure how this attaches to the existing wiring harness. I see a harness into the gps controller on the dash. The previous sync2 apim had only a large plug and the usb. It didn’t have a fakra plug. I don’t see anything that looks like a fakra connector.

It basically replaces the one behind you glove box. All it adds is the Blue plug and the signal separating box. The black and brown plug got to the ACM. blue plug goes to the back of the APIM, You prob know that part though.

I only have this pic of an Expedition behind the glovebox. It has jumper wires so it won’t look the same in a Mustang.

You probably have the first cable in your Mustang and it just needs to be replaced with this second cable. In most models it really just goes along the bottom of the glovebox opening.

On a 2013-2016 Fusion the connector for that sub harness is under the driver’s side of the console next to the shifter.
As far as the roof antenna, if you have Sirius in the car you should already have a dual coax and a power wire. If you have that you can use one from a later Mustang, shark fin from a Explorer that has/had Sync 3 or the regular antenna from 2017-2018 Fusion Ti/Plat or high trim SE.

Surprise, it does matter. This setting changes the voltage, thus the gain, of the antenna. Using the setting for IP with heated windshield is the highest voltage or gain setting for the antennas. Be aware that antennas are not all the same so some will perform better than others with these settings. Also, some LNA’s do not support variable voltage and are set for maximum gain. The values are optimized for the production antennas.


Finally had some time to re-visit this. Thanks for the help. I can report that the Xtenzi brand GPS with Fakra-C connector from Amazon appears to be compatible with Sync3 as I am not getting errors. Link to actual product, Secured with 3M panel tape to top of dash hidden under center dash speaker grill cover. I guess 3rd time is the charm. Errors with Eightwood and Bingfu brand.

I agree that tapping into the OEM antenna would be best. I did look behind the glovebox and below the armrest. The harnesses don’t appear to be quite like what you have in your images. I’m attaching them if it can help others doing the Sync2>Sync3 upgrade on a Mustang G6.

Wiring harness behind glovebox on left side.

. This looks the most like your two yellow cables but they plug into a yellow rectangular wiring harness shown in the image.

Wiring harness behind glovebox right side.

Wiring harness under armrest.

The 3rd pic is the one. On the Mustang it appears it goes down the middle like the Fusion. Good to know, Thx.

That blue one in the 3rd image looks like a Fakra. Would you use a splitter or simply run a Fakra type extension cable from that point? It’s interesting that all of the Sync3 upgrade guides simply suggest to install an aftermarket GPS, but then most of the cheap ones result in errors.

The aftermarket GPS is just the easiest. Most people are not mechanically inclined to swap the splitter and possible the antenna to do it. That and the seller does not want to go down the road of having to provide technical support on all that.

I would use the splitter for sure. I would need to look at the diagrams in Oasis to be sure how it is run but OEM has always been the better route on all this. IMO.