2014 r12gs tpms question

Folks
My 2014 R12GS TPMS indicator on the dash.
Cast wheels, 44000 miles
The front works fine, reads quickly after you start riding.
The rear works fine sometimes.
But about half the time, it reads "--" only.
And that can go on for a entire tank of fuel.
Then the next start, it works fine.
The triangle "warning" thing does not illuminate.
Any one have an idea of what to troubleshoot first and second.
I do have the GS 911 tool.
Thanks

David

Sounds like the typical weak battery, intermittent condition.

It's pretty easy to just replace the TPMS sending unit and then use a wake-up tool to capture the new serial number with the GS-911.

This may help.
https://youtu.be/4HAnT58b2DY

I recently replaced both the TPMS Sensors on my '16 RT, which has 78,000 km on the clock. I had been having intermittent flat tyre indication, or no readings for the rear some time. I had mine done by my local dealer, and the units were $270 AUD each. Gasp!!

Many alternative TPMS sources on Fleabay and Amazon for much less than =the OEM sensors - just search by the part#.
If replacing only one sensor the bike will detect and substitute the new for the old without the need for either a wake-up tool or a GS911 or Motoscan.

The sensors I bought from Amazon were $30 USD for two, look and feel exactly like the OEM, came with ID codes on the packaging.
I replaced both sensors at the same time, used my Motoscan to program the new ID's into the Computer.
I had a wakeup tool, you need one that works on a 433mhz sensor, and once awakened the sensors immediately readout on my dash.