LeafSpy Pro data accuracy...

[Lew]

I'm still learning my way around my 2019 SL Plus after a couple of months of ownership. I have questions about basic LeafSpy Pro (using LeLink BT-LE dongle) data.

1. Tire Pressure:
   LeafSpy consistently reports tire pressures of ~36-37 psi (hot and cold). Using a fill station I trust and 3 different tire gauges, I read 40-41 psi. Is this discrepancy normal? I presume the LeafSpy reading is correct from the CAN bus since the dashboard reads roughly the same.
   Could all 4 tire sensors be that far out of whack? Is there a calibration factor that the TPMS adds to the sensor data? If so, can that calibration be tweaked?
2. Ambient temperature:
   Unlike the TPMS, the ambient temperature LeafSpy reports is ~100-170+ degrees F. (on initial start and varying while driving but still unreasonably high all the time) but the dashboard and Infotainment are close to what the temperature feels like.
   This would indicate that the temperature reported via the CAN bus might be using a sensor from some other source than what is feeding the dashboard. Any guess as to where that sensor might be? Or if I just have an open connection in a cable somewhere? I don't have a service manual yet so any hints would be appreciated...

I'm presuming a different dongle wouldn't have any impact?

Any hints/pointers/advice appreciated...

 

[GerryAZ]

I am not sure what temperature you are looking at in LEAF Spy. There are battery temperatures and also motor inverter temperature (which will be significantly higher than ambient after driving for a few miles (depending upon motor load). I am not aware of ambient temperature display in LEAF Spy. The LEAF measures absolute air pressure in the tires, but tire gauges (and service station gauges) measure gauge pressure. They will be the same at sea level, but gauge pressure will be lower than absolute pressure at higher altitude.

 

[Lew]

The LEAF measures absolute air pressure in the tires, but tire gauges (and service station gauges) measure gauge pressure. They will be the same at sea level, but gauge pressure will be lower than absolute pressure at higher altitude.

This seems odd to me in that, based on this as I understand what you say, in Denver the pressure reading from the TPMS should be higher than the 40+ psi that I think are "right."

I am not sure what temperature you are looking at in Leaf Spy.

The reading is labeled on the screen is "outside temperature" which I presumed was ambient. Is that the inverter temperature you mention? I'll do more research but still find it unlikely that this temperature could be that high within a few seconds of turning the car on...

I'll do more looking into the LeafSpy manual and post a screen shot if that helps...

 

[GerryAZ]

I did not explain the TPMS measurements very well. The sensors are calibrated to read gauge pressure at sea level, but the sensing is actually absolute pressure. Since atmospheric pressure is lower at high altitude, a normal tire pressure gauge will indicate a higher pressure at high altitude than the TPMS sensors which are measuring absolute pressure and calibrated to display gauge pressure at sea level. Some gasoline engine cars use the barometric pressure sensor for the engine management system to calculate a correction for the TPMS system, but LEAF does not have a barometric pressure sensor so the system cannot compensate for altitude. The 4 psi difference is probably about right for the altitude in Denver.

I need to look at LEAF Spy screens more carefully to understand what temperature display you are looking at.

 

[Lew]

From the LeafSpy manual:

If the ambient number looks to be in the wrong units go to the Settings/Units panel and enable "Convert Outside Temperature" or if already enabled then disable it.

By turning this off, the readings are closer to reality but still a few degrees different from temp reported on the dashboard.