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Torque Converter Lockup & ScanGauge

12K views 31 replies 10 participants last post by  Bimmer74 
#1 ·
FYI:
I installed a ScanGauge 2 in my '10 Forester and have been playing with the various gauges that you can monitor. One of interest was "OPEN/CLOSED LOOP". By monitoring this gauge, you can tell when the torque converter swiotches from locked to unlocked and vice-versa.

As an example, let's say the engine has warmed up to normal operating temp (~185-195 deg. F) and your coasting down the road at 40 MPH with no foot on the gas. If you check the open/closed loop gauge, it will show "OPEN" and the MPG goes to 9999 which says the injectors are turned off and the transmission is free-spinning the engine.

If you let the car continue to coast, at ~20 MPH, the open/closed loop gauge will change to "CLSD" and the MPG drops to something less than 9999. Also, if you don't touch the brake while coasting down, there's a slight nudge when the torque convert unlocks.

I also tried this in my other car, an '04 Honda Pilot, and on that one the torque converter unlocks at ~30 MPH.

This might be handy if you suspect a torque converter lockup issue in your vehicle or if you just want some feedback on how often the torque converter switches from unlocked to locked. I've read some other posts where an unlocked torque converter is the main cause of the tranny temperature rising. Note, I don't know if this works for older generation Foresters.
 
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#2 · (Edited)
Glad you're enjoying the Scangauge II! We have one in each of our 3 vehicles. As to Open or Closed Loop operation, you might want to check out this link. :wink:

From the SG2 manual:
CLSD LP/OPEN LP Fuel system loop status This indicates when the oxygen sensor is being used to control the mixture (closed-loop) and when it is not (open-loop). It is usually closed except when the engine is cold or under full throttle acceleration.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
#3 ·
2.5x sleeper,
Yep -I'm aware of what is described in the link. My observations were taken after I had driven the Forester for ~10 miles/15 minutes (past the initial open loop stage). I monitored both the open/closed loop setting and the instant MPG and see the loop go back and forth between open and closed depending on the speed and if the accelerator is being pressed.

Have you ever played with this setting on your scangauge and do you see similar behavior?
 
#4 ·
My understanding is that when the O2 sensors are used to calculate the air/fuel ratio in closed loop mode, then the short term fuel trims come into play. I know these can be monitored with XGAUGE on the scangauge but I don't know what I would ever use the info for. Maybe you can detect if an O2 sensor is bad?
 
#5 · (Edited)
My main use for the Scangauge II is to monitor intake air temp, coolant temp, battery voltage & I like the digital speedometer, which is more exact & easier to read than the analog one in the instrument cluster. Of course the CEL code view & clear functions is a plus. :wink:

The SG2 uses the existing engine sensors that are tied to the ECU, so many of the functions are kinda interesting to monitor (view), but are really not of much use (for me). :smile:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
#6 ·
Yep -that's about the same conclusion I've come to. I mainly intend to use the scangauge as a trip computer. I really wish there was a way to monitor the tranny temp. I have read on some other threads that the tranny temp sensor goes to the TCU and not the ECU so it's not possible to read it from teh OBD2 port. :icon_frown:
 
#7 · (Edited)
From my understanding & research, the Scangauge II via XGauge functions can be programed to monitor any sensor that the ECM uses. I have to admit I haven't prusued these features, but my seaching the internet found this. It's not for Subaru, but if you read the the thread, you can see the SG2 can do much more if you want to get into it. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
#8 ·
Thanks for the link. I have to dig into the XGauge programming a bit. The scangauge manual and info on Linear Logic's website are pretty cryptic. I wish they would partner more with the various auto manufacturers to reveal more of the vendor specific data that can be shown with xgauges. From the XGAUGE.PDF document, it looks like they did a lot of work with Ford and GM but that's about it.
 
#9 ·
Resurrecting this old thread...

Has anyone with a Scangauge II and auto transmission Subaru been able to get transmission temperature readings? I don't want to buy it if it won't provide that info.

My highest priority "gauge" needs are:
Transmission Temp
Coolant Temp
Exhaust Gas Temp

I have an '04 Forester XT with auto trans.
 
#11 ·
... Has anyone with a Scangauge II and auto transmission Subaru been able to get transmission temperature readings?...
Transmission temp is not listed by ScanGauge as a regular function
» Fuel Economy
» Fuel Rate
» Battery Voltage
» Coolant Temperature
» Intake Air Temperature
» Engine Speed (RPM)
» Vehicle speed (MPH and KM/H)
» Manifold Pressure (not available on some vehicles)
» Engine Load
» Throttle Position
» Ignition Timing
» Open/Closed Loop
ScanGaugeII - Digital Gauges
The SG can be programmed to look for more information, depending on the car:
You can add vehicle specific gauges to your ScanGauge.
ScanGaugeII - Add-A-Gauge
Transmission temperature is one of the functions that the SG can display, but not for a Subaru. Evidently, this information is not known to the Subaru ECU and so is not put out through the OBDII port:
http://www.scangauge.com/support/pdfs/XGAUGE.pdf
 
#13 ·
I looked over the PDF for the Subaru select monitor & I couldn't find anything on trans temp. From what I see, the trans temp is kinda like the oil pressure light. It's off when normal & on when there's a problem. No real gauge like functions. :frown:

Curious... are you looking for one device to measure Transmission Temp, Coolant Temp & Exhaust Gas Temp? :confused:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
#18 ·
I monitor instant fuel mileage, MAP, IAT, and something else on my scan gauge. The trouble code reader is also worth it.

Just because the company doesn't offer the programming to pull the transmission temp doesn't mean that the device can't read it. I might dig through their forums to see if anyone's been successful. The only problem is if you use an x-gauge then you have to reprogram all of the generic gauges. That could be a PITA.
 
#21 · (Edited)
On another forum there was a quote from SOA's customer service spokesman John Mergen stating that the Tranmission Control Module(TCM) knows the trannie data, the ECU doesn't, so not available to scanners.

EDIT: The following statement is mine, not Mergen's:
TCM does pass some data to ECU such as transmission fault codes, throttle reduction during shifts, etc.

I'm still curious whether some of the active polling features of Xgauge could possibly tell the ECU to ask the TCM for temp data, but it does seem far-fetched.

PS- Scangauge list seems rather incomplete, but I did notice that the last update of the .pdf was August 2010 so they are definitely adding data.
 
#23 ·
Searching with Google a bit more..
I found an EndWrench article from early 2004 which includes quite a bit about the 4EAT transmission and has some schematics.
4EATPhase2.pdf

It looks like the TCM receives temp data, but doesn't send it to the ECU. Per the electrical schematic it does send data straight to the Subaru Select Monitor.


Then I found a .pdf discussing the Select Monitor functions- Not sure of the exact year:
Subaru%20Select%20Monitor.pdf

The only mention of AT data are AT fuel cut, retard, and torque control that affect shifting.

That's all I know, and it isn't much. Certainly I don't know whether the TCM provides any information to the OBD port.

(sorry, I can't post links because I'm new here- I think you can find those two files by using a search engine)
 
#25 · (Edited)
Okay, I dug through the 2004 Forester service pdf's.

ENGINE SECTION 3 (Pub.No.G8080GE4)
ENGINE (DIAGNOSTIC) EN(H4DOTC 2.5)

TRANSMISSION SECTION (Pub.No.G8080GE5)
AUTOMATIC TRANSMISSION (DIAGNOSTIC)4AT(H4DOTC 2.5)

Plug B40 4AT(H4DOTC)-25 in the transmission pdf is the OBD port, also shown on EN(H4DOTC 2.5)-23 of the engine pdf. Unfortunately I get confused because of the way Subaru labels their schematics- their pinouts are reversed from other OBD diagrams- I think because one is showing the M plug and the other F. Not a big issue but where Subaru says +12v battery is pin 1, in fact it's pin 16, etc. On both the transmission section and engine section, they show connections from both TCM and ECU to pin 10 (Pin 7 in everyone else's OBD schematic)

Anyhow per OBD-II standards pin 16 is +12v, pin 4 is chassis ground, and pin 7 is the "K-Line" data link for # ISO 9141-2 protocol.

Subaru's Transmission section refers to "CAN communication circuit" which may be different than the ECU's protocol, and doesn't seem consistent with the use of pin #7? Wikipedia has a section on "On-Board Diagnostics" which describes some of the protocols and standard uses of various pins.

Still more questions than answers, but I believe the wiring diagrams do show a direct connection between the TCM and the OBD-II port. It seems that the Scangauge ought to be able to pull data from the TCM with the right programming.
 
#26 ·
As I posted here, the ScanGauge II can't pull up data that doesn't exist. The reason you can't measure engine oil pressure, is that it's not measured. The only transmission temperature measurement I could find is like the engine oil pressure switch. Off or on to indicate the presence of oil pressure. In the case of the transmission, if it's overheated a sensor turns on a light. Nothing in the way of actual temperature measurement... that I could find. :frown:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
#27 ·
I don't know if this will help with getting trans temp on your scangauge, but if you want to see your trans temp and Lock-up duty cycle, the program i posted here: http://www.subaruforester.org/vbulletin/f89/legacy-gt-guys-making-good-progress-5eat-tcu-82232/ actually works and shows many transmission parameters, the only problem is it's in metric and you need a laptop.

However if those guys could make it work through the OBD-II port i'm sure it's only a matter of time before other people figure it out.
 
#31 ·
I'm not a berlios expert but this looks very interesting. Can the GUI interface for berlios be customized? Like if I wanted to run this on a tiny netbook and wanted to show 4-6 gauges at a time in large, easy to read numbers? I want something I can view quickly while driving.
 
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