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Driving in reverse makes GPS position wrong

Peter_M

Member
Oct 10, 2013
975
290
Ottawa, Canada
Has anyone else noticed this? If you reverse for any significant distance (e.g. backing out of a long driveway), the GPS position will not update while you're in reverse, so then it's off by that amount for 10-15 minutes until it gradually drifts back to the right place as you drive. This is usually just a minor annoyance, but if you're in an unfamiliar area and relying on directions, it can be a problem if the wrong position is on another street. It also messes up TeslaFi records.

This is in a Model S with 2018.14.2 a88808e.

I did search for this topic but let me know if there's already a thread on this. Thanks.
 
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MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
Hi Peter, I have been complaing to Tesla about this problem for over two years. Escalated it to executive resolution and all I get is a song and dance that they are working on it.RIGHT! My problem manifests slightly different. When I drive backwards the map icon moves forward screwing up the location by about 2.5 feet per 1 foot backed up. Exactly what you describe happened to me. I had to back up a very long driveway and the navigation was totally useless. It works correctly once right after a firmware update.
 
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Reactions: Peter_M

Peter_M

Member
Oct 10, 2013
975
290
Ottawa, Canada
To be honest, I didn't watch very closely so the same thing might happen for me - icon moving forward as I back up rather than just not moving. I'll check next time.
 

MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
Here is what I do. Set the map to full magnification. Put the car in reverse, touch the screen to close the rear camera and back up. I'm pretty sure that the icon will move forward.
Most people wouldn't see this because it's only visible at full magnification of the map. I also see the icon slowly drift back to the correct position as I drive forward.
This problem also will affect garage door auto close. The car ends up 300 feet in the field behind me and autoclose does not work.
I'm going to email Tesla again.
 

ken830

Model S 85, Model 3 Performance
Jun 19, 2012
1,113
367
San Carlos, CA
I had occasional GPS issues (such as losing satellites, drifting, or stuck map marker) that the service center has not been able to resolve since 2014. But recently, it completely stopped working (zero satellite connections so it drifts away from the actual location over two weeks) and the service center replaced everything including the GPS antenna and mcu. After they did that, I noticed that everything worked but I had issues with Homelink and suspension geofencing features and after some experimentation, noticed the forward-when-reverse issue. I took it back to the service center and showed the tech and he said would research the issue. I got a loaner and when I got home, I noticed that the loaner had the same issue! And that led me to search the forums and here I am. Shouldn't this bug be pretty widespread?
 

MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
I've tried for a long time to find out how many cars have this problem and did not have much luck. I think it's a software bug, not hardware. The GPS board was replaced which didn't help.
Please notify executive escalation. Up to now I feel like I've been spitting into the wind trying to get this problem fixed. If more people complain, Tesla might take more notice. All I get is they are working on it.
Thanks.
 

ken830

Model S 85, Model 3 Performance
Jun 19, 2012
1,113
367
San Carlos, CA
I've tried for a long time to find out how many cars have this problem and did not have much luck. I think it's a software bug, not hardware. The GPS board was replaced which didn't help.
Please notify executive escalation. Up to now I feel like I've been spitting into the wind trying to get this problem fixed. If more people complain, Tesla might take more notice. All I get is they are working on it.
Thanks.

From your signature, you also have a very early car. Did this occur when everything in the car was original (before GPS board replacement, etc.)?? Because I didn't see this in my car until after the latest service center visit where they replaced the GPS antenna, board, and MCU. So, I suspected the new MCU maybe not being compatible with the older drive computer so communication of being in "reverse" doesn't register. But now that I see this in the loaner (I'll have to test this some more) kinda throws all of my theories up in the air again.

The tech already says he would check all the hardware again and take videos and open a new issue in their system for the engineering team to resolve. I want them to escalate this, so I'm debating if I should mention the same behavior in the loaner yet. I'm afraid if I do, they will just claim it's normal behavior and return the car back in the same broken state.
 

MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
I noticed this problem over two years ago and started complaining. Normally this problem is not noticed because the map is normally not on full magnification. Plus once you drive forward a mile or two it corrects itself. Another interesting point is that after a firmware update it works correctly once, Until you drive forward.
I believe that this problem has been in the car since new, but a cannot say for sure.
The techs are clueless about this problem. And don't let them feed you a line of BS that this is normal.
 

deonb

Active Member
Mar 4, 2013
4,057
4,210
Redmond, WA
I noticed this problem over two years ago and started complaining. Normally this problem is not noticed because the map is normally not on full magnification. Plus once you drive forward a mile or two it corrects itself. Another interesting point is that after a firmware update it works correctly once, Until you drive forward.
I believe that this problem has been in the car since new, but a cannot say for sure.
The techs are clueless about this problem. And don't let them feed you a line of BS that this is normal.

Have you tried just a straight reboot and see if it will also correctly work once thereafter? If so, it's useful information to pass unto Tesla.
 

.jg.

Member
Feb 27, 2018
446
369
Weston Super Mare, England
This is interesting. I have to reverse up a lane to my garage and I have experienced some problems with the Auto-Open and Auto-Close functions of Homelink. I will check if my car's navigation system shows the same error when reversing.

As I understand it, Tesla uses GNSS modules from U-blox:
MCU1 cars :LEA-6R - GPS only (no GLONASS or Galileo), SBAS support, Automotive Dead Reckoning (inertial navigation, wheel pulses, etc.)
MCU2 cars: NEO-8L - GPS, GLONASS, Galileo simultaneously, SBAS support, Automotive Dead Reckoning
It seems that U-blox wont discuss the technical details of these modules but I understand the ADR functionality counts "wheelticks" to measure vehicle movement when there is no GPS lock. I wonder if the module only counts wheel pulses as forward motion, even if the car is reversing - and whether wheel pulse data overrides GPS data.
 
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MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
Auto open and auto close work off GPS. If I back down my 50 foot driveway, the auto close works, but if I have to immediately drive back up the driveway, the map shows me sitting in an empty field 100 feet away. Auto open fails.

This is interesting. I have to reverse up a lane to my garage and I have experienced some problems with the Auto-Open and Auto-Close functions of Homelink. I will check if my car's navigation system shows the same error when reversing.

As I understand it, Tesla uses GNSS modules from U-blox:
MCU1 cars :LEA-6R - GPS only (no GLONASS or Galileo), SBAS support, Automotive Dead Reckoning (inertial navigation, wheel pulses, etc.)
MCU2 cars: NEO-8L - GPS, GLONASS, Galileo simultaneously, SBAS support, Automotive Dead Reckoning
It seems that U-blox wont discuss the technical details of these modules but I understand the ADR functionality counts "wheelticks" to measure vehicle movement when there is no GPS lock. I wonder if the module only counts wheel pulses as forward motion, even if the car is reversing - and whether wheel pulse data overrides GPS data.
 

.jg.

Member
Feb 27, 2018
446
369
Weston Super Mare, England
I tried reversing up the lane to my garage, with the navigation map at maximum zoom but it seemed to keep the correct position throughout. However, the car was parked outside the garage for some minutes before I tried this - maybe it would be different if starting from inside the garage, where the GPS signal would be blocked and the GNSS module may be relying on the last know position and the Dead Reckoning function.
 

MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
Well, it sounds like yours is working correctly. Just out of curiosity does the icon flip around in the direction you are going or does it back up?
I'm suspecting it's a problem with the dead reckoning circuit.

I tried reversing up the lane to my garage, with the navigation map at maximum zoom but it
seemed to keep the correct position throughout. However, the car was parked outside the garage for some minutes before I tried this - maybe it would be different if starting from inside the garage, where the GPS signal would be blocked and the GNSS module may be relying on the last know position and the Dead Reckoning function.
 

.jg.

Member
Feb 27, 2018
446
369
Weston Super Mare, England
Well, it sounds like yours is working correctly. Just out of curiosity does the icon flip around in the direction you are going or does it back up?
I'm suspecting it's a problem with the dead reckoning circuit.
The icon stayed pointing forwards, against the direction of travel. I was moving slowly - about walking pace. I need to try another test, when the system has not had a chance to get GPS lock and hopefully, is using dead reckoning.
 

ken830

Model S 85, Model 3 Performance
Jun 19, 2012
1,113
367
San Carlos, CA
I think in mine, it still moves forward when I have GPS signal. It seems to override the GPS when moving slowly (which makes sense, since the resolution of GPS is quite low compared to a single wheel rotation).
 

.jg.

Member
Feb 27, 2018
446
369
Weston Super Mare, England
I tried another reversing test but this time, having just started the car in the garage (before GPS lock). The result was that the icon on the navigation map didn't move at all. It only started moving after a few minutes, presumably once GPS positioning was available.
My car has MCU1 and AP1.
 

MichaelS

Supporting Member
Aug 8, 2012
319
51
Hayward CA
Well, that is interesting. In my car the icon moves immediately. Sounds like the dead reckoning is not working correctly. Is there a tunnel you can drive through to kill the GPS signal and see if the icon stops moving?
By the way, the homelink is extremely unreliable when backing up to a garage since the transmitter is in front.
 

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