Pixhawk Preflight Fail: GPS Reciever Missing


I have a Pixhawk with M8N GPS module but it’s not detected on the preflight check. I’ve tried the latest firmware on both QGroundControl and APM Planner but neither detect the GPS module. The GPS port is providing ~5v so the module is getting power and all the connections on the GPS look good with no damaged cable.

Any ideas would be very welcome?

Thanks, Tim

Do you get any LED flashing on your GPS module? And are you sure it’s connected to the correct pin on pixhawk? Also might be worth double checking the pins on your pixhawk connector are not bent.

Have you completed the setup wizard as well where you can also perform compass calibration on the GPS module compass?

Evening Alex! Yes, done the compass calibration and it comes up green. The M8N is plugged in to the GPS and i2c sockets and the pins look unbent. The multimeter shows 5.25v between the outside pins of GPS. Checked the Serial 4/5 too and there’s no second GPS detected.

No LED on the M8N when it’s plugged in to either the GPS or Serial 4/5.

Some photos of the pins and the connector:
New photo by Tim Squires
Pins look good as do the wires on the connector, the positive wire looks a tiny bit frayed but OK.

It’s not been in the air yet. I have ordered another M8N from you (because the plane needs a backup GPS) which I can use to test to see if it’s a problem with the Pixhawk or the GPS module.

I was hoping that I’d just missed a setting in APM planner!

Thanks again, Tim

Sounds like you might have a bad m8n module, have you opened it up to check the solder points inside the module are all ok? If not if you purchased it from us just send support an email with your order number and a few pics/link to this thread and we will replace it for you

Not familiar with APM planner but in Mission Planner you can turn off individual pre-flight checks so try this for the GPS… providing… you know it’s actually working and your positive calibration would indicate that.
The main questions have to be…

  • Does it show any satellites on the GCS screen? any co-ordinate display etc.
  • Does the compass work? does the GCS screen bearing alter when you rotate it?

If it does than I’d be inclined to turn off and the check and give it a careful test flight.
As Alex @unmannedtech1 has already said though. if you don’t have light on the GPS puck then it might be a duff unit

Steve :slight_smile:

Yes, it’s bought from UnmannedTech but I didn’t want to open it incase it voided any warranty. Am I OK to take a look inside or should I send it back?


Hi Steve,

Yes thanks. It’s looking good for stabilized mode at least, the ailerons all move in the right direction when armed and I fly the plane round the dining room like a kid. :slight_smile: It also responds to the transmitter input.

I’ve just noticed that when the airspeed sensor and the M8N compass is plugged into the i2c splitter, QGroundControl reports that the airspeed sensor is missing too. Unplug the M8N and the airspeed sensor appears again.

No satellites found in GC when the GPS is plugged in either with or without the i2c compass plugged in.

I’m looking forward to receiving the second GPS module to I can test it out.

I do need two GPS modules eventually because this aircraft is planned for autonomous BLOS missions with automatic landing, which is going to be interesting…

Thanks again.

Looking good! Received the new GPS module today (thanks Alex) and it’s been detected. Compass and GPS working well. Yay!

Good to hear it …
Happy flying in 2017 :smiley:

Steve :slight_smile: