X-gauge Scangauge command to monitor actual main tank fuel directly?

[Greasemonkey Lurker Find all posts View Profile Close Greasemonkey]

Thanks ExNissan and RPP to come up with the programming. I can confirm codes to work in my Prado 150 MY2014 1KD-FTV face lift. Haven't done a compare with a computer based diagnostic read, but X-gauge main tank shows 86l and sub is empty. The calculated liters to empty by the Scangauge is 87l and have this calibrated to work quite well based actual refueling amounts to full. So as a plausibility check display is spot on. I actually prefer this as a raw read without averaging, instantaneous sensor feedback is better for diagnostic purposes. If one wants an accurate read then just stop the car and make sure its level, but I can't really see a purpose for doing this. All one needs to know is that sub is kept absolutely empty with a less than full main tank level. Liters to empty is a better trip planning tool, provided the transfer system works.

Again thank you for coming up with the coding!

[RPP Senior Member Find all posts View Profile Close RPP]

My thanks to ExNissan also.

Looks like the Sub Tank drains first, and the Main Tank refills first (I think it then overflows to the Sub Tank - you can hear the fuel gurgling up the pipe just before it overflows into the Sub Tank).

Therefore, if the filter chokes, just keep the Main Tank topped up.

[Greasemonkey Lurker Find all posts View Profile Close Greasemonkey]

Hi RPP,
Not quite, the engine only draws fuel out of the main tank, but the fuel return line (excess for injector cooling purposes) goes back to the sub tank not the main (on the 150 Prado with sub tank). Its a clever system, but the whole system needs to be all working. In the worst case you can actually have the situation of a full sub tank while main is dry and engine stops. Standard vehicle gauge will show you that you have fuel, but being in the sub tank it is not available to the engine. So work around is to keep combined fuel levels above that of the sub, ie to be on the safe side anticipate to run dry when vehicle gauge gets down to half full. With the X-gauge read outs the situation can be monitored a bit better. The situation shouldn't happen with the service schedule being followed, but remote area travelers are bit paranoid.

[RPP Senior Member Find all posts View Profile Close RPP]

ty Greasemonkey,
I'm now one of them paranoid types.
Got 4 flat tyres in the Kimberley last year, 3 in one day. Now I carry all manner of spares and tools.

[Guest Close Guest]

The following are for Torque Pro - I'm sure someone can translate them for X-guage

Main tank in L
PID 2129
Equation AVG(20:A/2)
OBD header 7c0

Sub tank in L
PID 212a
Equation AVG(20:A/2)
OBD header 7c0

Notes:
1. AVG(20: Gives the avererage of the last 20 readings - the tank level is instantaineous and moves around a fair bit
2. The value returned by the OBD query is in 0.5L increments hence the A/2

Cheers
-Rod

Thank you ExNissan for the info.
I tried the above on torque Pro on my 120 Grande with M-OBD (I realised this is in the 150 section) and unfortunately, I'm getting nothing. If anyone else has any luck, do report back.

[peter_mcc Senior Member Find all posts View Profile Close peter_mcc]

Looks like the Sub Tank drains first, and the Main Tank refills first (I think it then overflows to the Sub Tank - you can hear the fuel gurgling up the pipe just before it overflows into the Sub Tank).

Therefore, if the filter chokes, just keep the Main Tank topped up.

If you look under the car you can see the filler pipe - there is a "T" junction with the straight ahead path going to the main tank and the leg of the T going to the sub tank. If you use a diesel bowser the flow is high enough that the main tank fills first - the diesel goes past the junction. However if you are filling it with a jerry can on the side of the road it will fill the sub tank first - if that happens you need to completely fill the sub tank before diesel goes into the main tank.

When my car ground to a halt on the Mitchell Falls Rd in the Kimberley with a clogged transfer filter I had 1 x 20l jerry of diesel - this wasn't enough to fill the sub tank so I had to beg/buy another 20l from a random passer by.

If you can keep the main tank filled up enough you'll be fine. The problem I see is that unless you're watching the two tank levels you won't know when it's all going bad.

[RPP Senior Member Find all posts View Profile Close RPP]

Hi peter_mcc,
thanks for the feedback.
It must have been hot, sweaty & dusty under the car on the Mitchel Plateau. I drove 9Km on a flat tyre after a long days traveling just to get to Home Valley Station and away from the 38 degree heat and choking bulldust on the Gibb River Road.

I had assumed, if the time came, that I could just remove the clogged filter and run a straight thru hose or replace it with a spare.
But I think the mechanism by which the main tank is topped-up by the sub tank requires the main tank to be full.

With the codes in my Scangauge I can keep an eye on it now.
Have you tried the codes?
My readings a tad low, the MATH might need a +6 offset. But I'm not sure because the sensors seem to max out before the tanks are completely full.

[Atherton Senior Member Find all posts View Profile Close Atherton]

Thank you ExNissan for the info.
I tried the above on torque Pro on my 120 Grande with M-OBD (I realised this is in the 150 section) and unfortunately, I'm getting nothing. If anyone else has any luck, do report back.

Works fine for me mate in my 150. Tried to attach photos but the forum isn't letting me at the moment :/

[Guest Close Guest]

Works fine for me mate in my 150. Tried to attach photos but the forum isn't letting me at the moment :/

Ok, must be the MOBD protocol then. I recently updated Torque Pro and noticed that transmission temp no longer works when it used to on one of the default meter choices.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

I tried the noted Scangauge codes but the results appear strange. The sub tank reading dropped from around 35 litres to 0 litres way to rapidly to be remotely consistent with actual fuel usage. The Main tank started on 83 litres, and remains on 83 litres well after the subtank reached 0 litres.

According to the dash fuel gauge I have approx 85 litres remaining so perhaps the main tank reading will start dropping shortly????

I have a 2.8l 2018 Prado if this makes any difference....

[RPP Senior Member Find all posts View Profile Close RPP]

Ahoy Aquanaught,

I also have a 2018 GXL Prado. I've been watching my Scangauge fuel tank readings for a few months now.

My Notes:
When both tanks are full the Xgauges read 55Lts & 83 Ltrs. So there are quite a few ltrs above the max reach of the sensors not being registered.
I.e. the sensors don't seem to be able to read past that point - even tho I know I have 150 Ltrs total.

When the Sub Tank is empty - 0Ltrs the Main tank takes a while to drop to below 83 ltrs. Then, when the Main tank drains to 75Ltrs, exactly half the total fuel carrying capacity, the Toyota fuel gauge on the dash also reads 50%. Therefore all good.

As for your sub tank reading dropping from 35 to 0 ltrs inexplicably quickly I can't say. I think your Xgauges seem to be behaving correctly otherwise.

My Xgauge readings after many re-fuelings have been behaving in a predictable manner, and I watch em, and the DPF readings, and the ATF Temp readings, like a hawk!.
I have 2 Scangauges daisy-chained so that I can see 8 gauges at a time.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

Thanks for that RPP. I will await the anticipated dropping of the main tank which should happen shortly, and then see what happens when I fill up next time.

It is curious that the sensors don't provide for the full tank range as the Toyota fuel gauge appears to indicate the full range and presumably is based on sensor signals. Perhaps it makes some assumptions as to the total fill level when above of the sensor upper limit, and tries to fill in the gaps with fuel usage rates to give an approximate reading when out of the sensor ranges.

Even if not providing an exact reading it would at least appear to provide useful info for problem solving should the transfer filter/pump etc fail.

[RPP Senior Member Find all posts View Profile Close RPP]

Even the Toyota fuel gauge on my dash has the needle sitting on (or past) full for a long time before it begins to drop.
It looks like the sensors cant sense whats in the very top of the tanks let alone in the various hoses.

However, when my Toyota fuel gauge reads 50%, my Main Tank Xgauge reads 75Ltrs, which is a match.

[Aquanaught Lurker Find all posts View Profile Close Aquanaught]

That is good to know RRP. Once the readings are "calibrated" against known fuel levels I can use it with more confidence. Thanks for working out and providing the Scangauge codes.

[Prone Member Find all posts View Profile Close Prone]

I have a 2018 VX.
The fuel quantity readings I get on the scangauge agree with those that RPP has reported i.e. 83L and 55L when full. Also the partial tank figures and behaviour are very close to the same as he has reported.

Cheers
Prone