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Discussion Starter · #1 · (Edited)
The ScanGauge I ordered yesterday was at the front gate before I woke up this morning. I'm working my way through the docs now. The firmware is at version 6.2

There's nothing in the manual for programming custom X-Gauges for the two things I was most interested in monitoring based on all the discussions here about aux coolers for the ATF and PSF for towing.

My 2012 EX-L 4WD apparently comes with OEM coolers for both ATF and PSF ... although I've yet to find the power steering fluid cooler. It is supposed to be a pipe with fins that returns the PSF from the steering rack back to the reservoir going across the front of the radiator. I see a pipe there but it is fin-less.

On the ScanGauge site I did find custom programming for the Honda CANLF codes for ATF temperature. » Honda-Acura

But so far, no sign of any codes for power steering fluid temp. Anyone know what they are?

I'm starting to wonder if I'm PITW on this as I can't find any blowups or part numbers showing the location (or existence) of a power steering fluid temperature sensor. :eek:

I got it through Amazon so I have a month to return it in case I can't find something other than ATFT useful. Idears welcome.
 

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Must set up a gauge for it using these perimeters.
OBD2 Mode and PID: 222201
Long Name: Transmission Temp F
Short Name: ATF Temp
Minimum value: -40
Maximum value: 300
Scale factor: x1
Equation: AA*(9/5)-40
Overrides PID: "Does not override any PIDs"
 

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Discussion Starter · #3 ·
Must set up a gauge for it using these perimeters.
OBD2 Mode and PID: 222201
Long Name: Transmission Temp F
Short Name: ATF Temp
Minimum value: -40
Maximum value: 300
Scale factor: x1
Equation: AA*(9/5)-40
Overrides PID: "Does not override any PIDs"
Thanks but I'm not sure how to do that.

I got this off the ScanGauge site for CANLF codes for the Honda/Acura transmission fluid temp. But nada for PSF temp.

143347
 

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To my knowledge, there is no sensor in the power steering system to read temperature.

The factory PS fluid cooler is in fact just a tube with no fins. The AWD versions get a longer tube.

This jurist is not convinced that towing adds any significant steering load or heat to the fluid, except when you are parking or placing the trailer backing up, when there's minimal or less airflow across the cooler tube. No more heat generated, just less carried away by that cooler tube. My towing is limited to a small (under 1/2T gross) utility trailer, so I can find no need to upgrade the PSF cooler.

HTH!
 

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To my knowledge, there is no sensor in the power steering system to read temperature.

The factory PS fluid cooler is in fact just a tube with no fins. The AWD versions get a longer tube.

This jurist is not convinced that towing adds any significant steering load or heat to the fluid, except when you are parking or placing the trailer backing up, when there's minimal or less airflow across the cooler tube. No more heat generated, just less carried away by that cooler tube. My towing is limited to a small (under 1/2T gross) utility trailer, so I can find no need to upgrade the PSF cooler.

HTH!
The load distribution hitch can put more weight on the front tires causing the pump to work harder. This equals more heat.
Poor Honda Pilot.
 

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Discussion Starter · #6 ·
To my knowledge, there is no sensor in the power steering system to read temperature.

The factory PS fluid cooler is in fact just a tube with no fins. The AWD versions get a longer tube.

This jurist is not convinced that towing adds any significant steering load or heat to the fluid, except when you are parking or placing the trailer backing up, when there's minimal or less airflow across the cooler tube. No more heat generated, just less carried away by that cooler tube. My towing is limited to a small (under 1/2T gross) utility trailer, so I can find no need to upgrade the PSF cooler.

HTH!
Thanks, it does ... but wasn't exactly what I wanted to hear (no PSF temp sensor). Look at several sites and I couldn't find one on any parts blowup.

I think where I got the impression the tow pkg had a PSF cooler with fins was from a listing for this part: Genuine OEM 2012-2015 Honda PILOT 5-DOOR Cooler, Power Steering Oil 53765-SZA-A51 | Honda Factory Parts
 

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You can mount an aftermarket auxiliary secondary PSF cooler......just got to get creative. Do a search within the forum and you will find pics of how others have mounted PSF coolers. I would think knowing engine coolant temp (ECT) and tranny fluid temp (TFT) would be preferable to knowing PSF temp, but that’s just me. I switch my SGII around to display volts, VCM on/off, etc. I’ve also used it to help neighbors read/clear DTCs when they had a check engine light. Handy little tool.

Creative Piloteer, aggrex, did this to his Pilot.

 

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The load distribution hitch can put more weight on the front tires causing the pump to work harder. This equals more heat.
Poor Honda Pilot.
A little technical, but...

Consider, if you will, that the work the pump does is pretty much the same whether you are moving the steering wheel or not. No heat is added in the rack, and fluid that doesn't do any of that "work" is bypassed back via that same spool valve that guides fluid through the rack. Fluid is directed through the rack or back continuously; "heavy" load on the rack just routes fluid differently on its way back to the reservoir and the pump. It's the pump that actually contributes all the heat, more dependent on engine/pump speed than much else.

The temperature increases when there's less airflow or capacity to shed that heat in the cooler. So long as it reaches an equilibrium at less than about 200F, should be OK.
 

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A little technical, but...

Consider, if you will, that the work the pump does is pretty much the same whether you are moving the steering wheel or not. No heat is added in the rack, and fluid that doesn't do any of that "work" is bypassed back via that same spool valve that guides fluid through the rack. Fluid is directed through the rack or back continuously; "heavy" load on the rack just routes fluid differently on its way back to the reservoir and the pump. It's the pump that actually contributes all the heat, more dependent on engine/pump speed than much else.

The temperature increases when there's less airflow or capacity to shed that heat in the cooler. So long as it reaches an equilibrium at less than about 200F, should be OK.
Its always been my understanding that more load on the PS system would equal more heat.
 

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Discussion Starter · #10 · (Edited)
A little technical, but...

Consider, if you will, that the work the pump does is pretty much the same whether you are moving the steering wheel or not. No heat is added in the rack, and fluid that doesn't do any of that "work" is bypassed back via that same spool valve that guides fluid through the rack. Fluid is directed through the rack or back continuously; "heavy" load on the rack just routes fluid differently on its way back to the reservoir and the pump. It's the pump that actually contributes all the heat, more dependent on engine/pump speed than much else.

The temperature increases when there's less airflow or capacity to shed that heat in the cooler. So long as it reaches an equilibrium at less than about 200F, should be OK.
I agree with that analysis ... to a point. Yes, the pump generates most of the heat, not so much the rack which "sees" the load. But that load or force is hydraulically transferred back to the pump which has to work harder which generates more heat.

If opening the bypass against the resistance of the spool valve was all the work the pump had to do, then the system should reach no higher temperatures steering back into a tight parking spot with a trailer than sitting at a red light assuming similar low rpms in both cases.

If so, then the system is under designed and a PSF cooler is a good idea whether you back loads into camping sites or not. Which raises concerns in my mind as to if a plain return pipe as a cooler is as sufficient as one with cooling fins. Why make both? (other than as a marketing revenue generating ploy).
 

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Must set up a gauge for it using these perimeters.
OBD2 Mode and PID: 222201
Long Name: Transmission Temp F
Short Name: ATF Temp
Minimum value: -40
Maximum value: 300
Scale factor: x1
Equation: AA*(9/5)-40
Overrides PID: "Does not override any PIDs"
Those parameters are only for the 'Torque Pro' software on the Android devices.
 

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Discussion Starter · #12 ·
Those parameters are only for the 'Torque Pro' software on the Android devices.
Thanks ... since I have all of one day's experience with this ScanGauge, I was wondering where to enter those values. I'm not sure I'll keep this gizmo though. I've come across some ways to custom program other OBDII dongles using an iPhone. I have some older iPhones and iPads gathering dust and I think I could use one as a dedicated "meter" for the Pilot and heaven knows there's plenty of ways to mount them in a car plus the iPads have a lot bigger, higher resolution, screen than the ScanGauge ... and the price is right. (we have to pay off the iThings when upgrading)
 

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NG, I had to do a little rethinking on my speech content above. Specifically, towing usually involves higher RPM's as the transmission stays in lower gears with the additional load. So likely more heat is added by the pump when towing.

TL;DR:

The rest of the process analysis is valid. The pump works at a constant load, and can't see which path the fluid is taking once it leaves the pump outlet. The pump has an internal bypass valve that sets the maximum pressure the system will see. Otherwise, everything that the pump pumps goes to the steering rack. At the steering rack, there's a "spool valve", a little barrel-shaped hydraulic fluid valve that directs fluid to the steering rack cylinder based on the difference between steering wheel position and rack position. When there's no difference, fluid is directed back to the reservoir and pump again.

No heat is added at the rack or spool valve, regardless of how much force is applied inside the rack by the flow directed by the spool valve. All that heat comes from the pump. The pump is a mostly positive-displacement device, so for every pump revolution there's a volume of fluid pumped. That internal bypass valve returns fluid to the pump intake when pumped volume exceeds what the system is accepting, but otherwise, everything circulates through the spool valve. Look at the rack and you'll see that the external hose connections are at the spool valve sitting just above the pinion. There are balancing passages or tubes between the ends of the rack housing, but ultimately all the fluid is returned to the reservoir whether there's a pressure difference in the rack caused by that spool valve or the valve recircs fluid directly back.

The spool valve itself is a thing of mechanical beauty. Down the middle there's a torsion bar spring that twists when you turn the steering wheel connected at one end, relative to the pinion gear attached at the other end. Sliding sections direct hydraulic fluid to different levels in the valve, each connected to one of four available passages in the housing. Fluid pressure/supply and return hoses connect, and the two rack chambers right and left also connect. The amount of twist applied to that torsion bar spring determines the direction and volume of fluid flow. Incoming fluid might go to one end of the rack while the other end vents to the return hose. A fraction of it might go directly from pressure to return hose when there's no deflection of the torsion bar spring. The "feel" of the steering is based on the stiffness of that torsion bar spring too. "Soft" means lots of assist and a fairly numb feel. A stiffer spring means less assist, and more of your steering wheel input is transferred mechanically to the pinion and ultimately the rack and tie rods.

No actual heat-generating work is done at the rack, regardless of how much twisting the spool valve sees. The pump sees a consistent flow and outlet pressure at any specific pump speed, regardless of how the spool valve directs the fluid on its way back to the pump. Faster pump speed means more fluid is pumped and more is bypassed internally directly back to the pump inlet.
 
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