- :
- 2022 CX-5 Turbo
This is going to be long, but I solved the mystery myself, and thought that I should share the
experience with you all.
I had a video recorder installed myself next to backview mirror. It draws power from the
12V socket below the radio. The video recorder is automatic. It starts recording once power
is on. Close the last AVI file when power is down using small internal battery. No worry for
me to do anything. It keeps recording everything happened out of my windshield (w/ audio).
It uses micro SD card, and records in cycles. I have it installed to record good/bad things happen
along the ways. Very useful in unfortunate events of accidents to clarify faults.
Let me put that aside for now.
Since a few months ago, my GPS started to act strangely. Sometimes, it located me
in places 50 miles away or even in rivers or the Pacific ocean. This happened a couple
times in the past (roughly once every month). I did the map calibration, and it went back
to normal. Most recently I had a trip to UC Berkeley. I got stuck in traffic for at least one hour.
The GPS started to act up again! It was actually funny to see yourself in the bay while driving
on highway. My engineer side took over. I got to solve this problem.
I dig through the WorkShop manual. The diagnostic was simple. It was either the antenna behind
the MID (display) or replacing the unit (~$2000-3000). Naturally, I hope it was the former.
So, I started a "debugging" process.
I got into the diagnostic mode and monitor the GPS signals. Nada! What?! It saw 0 satellite.
I recalled that I was seeing at least 4 to 5 satellites last time I check the same page.
Conclusion: GPS signals were not received.
Wait: During the past few months, I have used the GPS guidance several times.
How did it work? Got it. Our factory GPS takes input from steering angles and VSS (vehicle
speed sensor). It is capable of "extrapolating" your current locations and applies some
heuristics to map your locations fairly accurately in "most cases". Then, I recalled that
most times when locations were wrong, I was stuck in traffic for a while. The "extrapolation"
process must have been messed up. It started to deviate to never-never lands...
OK. That made sense to me as an engineer.
So, no GPS signals visible? In perfectly good weather? No way.
The WorkShop manual asks to disconnect all
aftermarket-installed devices (including Mazda installed accessories like Remote Start, etc.)
It also says that When you see "GPS" three letters displayed at the top/left corner below
the compass, that means your GPS is receiving the signals from satellites.
So, I disconnected the aforementioned Video Recorder. Guess what? Bingo!
The navigation was displaying "GPS" three letters below compass. The diagnostic mode confirmed
that 4-5 satellites were visible. Great! Problem solved.
I did not stop here.
So, interference is blocking GPS signals to be visible by the navigation unit.
I dig in more.
Once GPS was displayed, I plugged in the Video Recorder. Guess what? No problem.
The GPS letters stay on the screen for the entire trip.
Another experiment. I plugged in Video Recorder, started the engine. The "GPS"
was not displayed at all (i.e. failed to acquire GPS signals from sky). I then unplugged
the power of Video Recorder, and the "GPS" came back in about 1-2 minutes.
Conclusion:
When navigation unit starts up, it tries to acquires GPS signals from sky. This is when
navigation unit is very vulnerable to interferences. Once GPS signals are acquired, it is more
tolerant to interferences (i.e. plugging the Video Recorder did not disrupt the GPS signals).
When GPS signals are not present, the navigation would keep trying to acquire them.
That is why after I unplug the Video Recorder, the GPS signals can be acquired
quickly.
So, if you do not see the "GPS" letters below your navigation compass, you have got a problem.
Some devices might be interfering the reception of GPS signals. Also, if your navigation
unit is not accurate sometimes, check and make sure "GPS" letters are displayed there.
Case closed.
I still need to find a solution to have both work in harmony.
experience with you all.
I had a video recorder installed myself next to backview mirror. It draws power from the
12V socket below the radio. The video recorder is automatic. It starts recording once power
is on. Close the last AVI file when power is down using small internal battery. No worry for
me to do anything. It keeps recording everything happened out of my windshield (w/ audio).
It uses micro SD card, and records in cycles. I have it installed to record good/bad things happen
along the ways. Very useful in unfortunate events of accidents to clarify faults.
Let me put that aside for now.
Since a few months ago, my GPS started to act strangely. Sometimes, it located me
in places 50 miles away or even in rivers or the Pacific ocean. This happened a couple
times in the past (roughly once every month). I did the map calibration, and it went back
to normal. Most recently I had a trip to UC Berkeley. I got stuck in traffic for at least one hour.
The GPS started to act up again! It was actually funny to see yourself in the bay while driving
on highway. My engineer side took over. I got to solve this problem.
I dig through the WorkShop manual. The diagnostic was simple. It was either the antenna behind
the MID (display) or replacing the unit (~$2000-3000). Naturally, I hope it was the former.
So, I started a "debugging" process.
I got into the diagnostic mode and monitor the GPS signals. Nada! What?! It saw 0 satellite.
I recalled that I was seeing at least 4 to 5 satellites last time I check the same page.
Conclusion: GPS signals were not received.
Wait: During the past few months, I have used the GPS guidance several times.
How did it work? Got it. Our factory GPS takes input from steering angles and VSS (vehicle
speed sensor). It is capable of "extrapolating" your current locations and applies some
heuristics to map your locations fairly accurately in "most cases". Then, I recalled that
most times when locations were wrong, I was stuck in traffic for a while. The "extrapolation"
process must have been messed up. It started to deviate to never-never lands...
OK. That made sense to me as an engineer.
So, no GPS signals visible? In perfectly good weather? No way.
The WorkShop manual asks to disconnect all
aftermarket-installed devices (including Mazda installed accessories like Remote Start, etc.)
It also says that When you see "GPS" three letters displayed at the top/left corner below
the compass, that means your GPS is receiving the signals from satellites.
So, I disconnected the aforementioned Video Recorder. Guess what? Bingo!
The navigation was displaying "GPS" three letters below compass. The diagnostic mode confirmed
that 4-5 satellites were visible. Great! Problem solved.
I did not stop here.
So, interference is blocking GPS signals to be visible by the navigation unit.
I dig in more.
Once GPS was displayed, I plugged in the Video Recorder. Guess what? No problem.
The GPS letters stay on the screen for the entire trip.
Another experiment. I plugged in Video Recorder, started the engine. The "GPS"
was not displayed at all (i.e. failed to acquire GPS signals from sky). I then unplugged
the power of Video Recorder, and the "GPS" came back in about 1-2 minutes.
Conclusion:
When navigation unit starts up, it tries to acquires GPS signals from sky. This is when
navigation unit is very vulnerable to interferences. Once GPS signals are acquired, it is more
tolerant to interferences (i.e. plugging the Video Recorder did not disrupt the GPS signals).
When GPS signals are not present, the navigation would keep trying to acquire them.
That is why after I unplug the Video Recorder, the GPS signals can be acquired
quickly.
So, if you do not see the "GPS" letters below your navigation compass, you have got a problem.
Some devices might be interfering the reception of GPS signals. Also, if your navigation
unit is not accurate sometimes, check and make sure "GPS" letters are displayed there.
Case closed.
I still need to find a solution to have both work in harmony.
Last edited:
