AT OIL TEMP LIGHT FLASHING- 2001 OB (L.L. BEAN) W/ 4EAT TRANS

[burtman]

My daughter purchased used Bean OB (2001 Outback/L.L. Bean; 3.0 Engine, 4EAT transmission) in April, 2019 with ~ 147K miles. AT Oil Temp light issues (see below) started @ ~ 154,500.  I’m am fairly experienced with working on cars, but this is my first Subaru.  Experience with transmissions is limited to basic maintenance/service. 

Overall the OB looks to be in pretty good shape – engine runs great, ride is solid, etc.  I’m now debating whether to try and fix the OB or just cut my losses and consider buying my daughter another vehicle.  I have extensively researched the” AT Oil Temp light flashing” issue online, and would GREATLY appreciate any advice offered on what my best options are…fix the OB or get rid of it and cut my losses?

And for all you fathers with daughters out there, this is a classic “rescue daddy” situation.  I would much prefer to fix the OB if possible as this is my daughter’s first experience buying a car on her own.  I’d like for it to not be seen as a tragedy by her (just maybe with a lesson learned that asking dear ol’ Dad for help early is a good thing). 

Current Symptoms

–     AT Oil Temp light flashing Code 79 (Transfer duty solenoid) with OB going into AWD mode (torque bind, etc.) as soon as AT Oil Temp light starts flashing.

–     AT Oil Temp light flashes and goes into AWD mode whether in normal or 2WD drive mode (fuse inserted)

–     BUT…the OB will go much longer/farther in 2wd mode (fuse in) before symptoms arise than in normal mode (fuse out)

–     Definitely temperature related more than miles driven - AT Oil Temp light never flashes in cool weather or when driving through rain.

–     And AT Oil Temp light stops flashing once car is cooled down, only to arise again after being driven in hot weather, stop & go, etc..

–     Also…Check engine light recently came on with code indicating misfire on cylinders 2 & 4.  I believe this in unrelated but wanted to mention just in case.  Probably just needs new plugs?

Maintenance performed (so far)

–     Completed 3 drain/refills on trans fluid, with new trans filter installed on 3rd drain/refill.  This seemed to offer some improvement in that OB now goes further/longer before AT Oil Temp light flashes and AWD mode kicks in.

–     1^st drain refill indicated that trans fluid had likely never been changed/serviced.  VERY dark brown (nasty stuff). 

–     Also completed 2 drain/refills on rear differential and 1 drain/refill on front differential.  No noticeable improvement noted.  Condition of drained differential fluid reasonable, with no noticeable contaminants or metal shavings present (I’ve seen much worse).

I went to a highly recommended local independent Subaru shop and was told that if AT Oil Temp light flashes and AWD symptoms arise in 2WD, problems are deep within transmission and the only fix is to replace transmission at minimum of ~$2,500.  I was about ready to write the OB off at that point, but after looking into issue a bit further online, I question whether this is truly my only remaining option.  Based on what I have been able to find, it looks like a DIY project to replace the transfer duty solenoid & clutch plates will very likely resolve the issue and get the OB back on the road again.

Is there anything else I missed that I should consider as possible solution/fix? 

If not, is it worth the effort to try replacing the transfer duty solenoid myself (along with clutch plates)?  I’ve looked online, and I believe this is something well within my capability. But it is a helluva project, and I don’t want to do it unless there is at least a reasonable chance of success.  The best link I found for transfer duty solenoid replacement is at https://forums.nasioc.com/forums/showthread.php?t=2501432.  Any advice, suggestions, references, links, etc. are much appreciated.

Finally, before considering replacing the transfer duty solenoid myself, I thought I’d do one more drain/refill of trans fluid and add BG ATC additive to see if this helps.  Sound reasonable?

The over-riding question to all you Subaru enthusiasts out there is, “What would you do if you were me?”

Thank you so much in advance for any assistance offered.  My first post here (great website)…hope it is OK.

[GeneralDisorder]

Get it warmed up and check the resistance through the solenoid at the bulkhead harness connection. Usually around 35 ohms. If that checks out you will have to check the wiring back to the TCU. If it doesn't you will have to pull the solenoid out and check it as well as checking the transmission sub-harness for high resistance or shorts. 

The "Subaru" shop you took it to obviously is isn't much of a specialist if they can't fix a pre-05 Duty-C failure. 

GD

[burtman]

Thanks bud...will do.  Certainly would be better if it is a wiring issue back to TCU or sub-harness issue.  It might be a day or 2, but I'll let ya know what I find.  

[burtman]

After carefully studying the FSM A/T Control System schematic & digging a bit deeper into the harness setup, I walked through the troubleshooting diagnostics in the FSM and got the following:

Step1 – Check transfer duty solenoid

• PASSED @ 12.6 ohms; within req’d 10-17 ohm
• Also checked at B54 conn @ TCM (#15 - #16/ground) and got almost exactly the same resistance
• GeneralDisorder stated I should get 35 ohms?  Huh?

Step 2 – Check harness between TCM & Transmission 

• PASSED @ 0.2 ohms; less than required 1 ohm

Step 3 – Check harness conn between TCM & transmission

• Passed @ OL; greater than req’d 1 Mega-ohm

Step 4,5 – Check TCM output signal in “P”

• PASSED @ 0.139V; less than req’d 1V
• Note: For steps 4,5,6 -  I measured voltage from back side of B54 connector @ #15 while plugged into TCM.

Step 6 - Check TCM output signal in “D”

• FAILED @ 4.05V; less than req’d 5V to 7V range
• Per FSM, indicates "poor contact” in xfer duty solenoid circuit OR replace TCM

I'm not sure how to test for poor contact in xfer duty solenoid short of taking it out (and replacing).  And if this doesn't fix it, I assume replacing the TCM is my next step?

I still have to check resistance through transfer duty solenoid when engine is hot and AT temp light is flashing (AWD is triggered).  I plan to do this tomorrow.  I'll post what I find.

Anyadvice and guidance from you Subaru experts is invited and much appreciated...

[burtman]

Just got through test drive. FWD fuse out. AT Oil Temp Light came on. Pulled over to take readings...

• Checked at B54 conn @ TCM (#15 -ground); R = 17-20 ohms
• Checked at B54 conn @ TCM (#15 - #16); R = 20-24 ohms

Seems to me that the above should be much closer to the same values? And both should be within 10 -17 ohm range per FSM.

• Left engine running, checked voltage @ B54, #15 to ground
  • 12.68 V in "P" (should be < 1V)
  • 12.68 V in "D" (should be between 5 and 7 V)

Any ideas? Do readings make any sense at all? Do I need to check again?

BTW...I have checked to the best of my ability and I do NOT have VDC.

Help Please?

[burtman]

OK...I have checked and double-checked readings:
When engine is hot and AT Oil Temp Light flashes:

• Transfer duty solenoid resistance is between 20+ to 24 ohms.
• NOTE: Resistance readings tends to drop rather fast – I had initial reading in high 20’s up to 30+ (depending on how fast I could get to location with meter). I assume this is due to temperature?
• TCM output voltage in “P” & “D”” is 11.83V

When engine is hot and AT Oil Temp Light NOT flashing:

• Transfer duty solenoid resistance is 33 ohms (steady)
• TCM output voltage in “P” is 0.16V (PASS)
• TCM output voltage in “D”” is 4.49V (FAIL > req’d 5 V min), which is very close to the 4.05V initial reading I got with engine cold

I pasted below a table I created with readings…hope it comes through
 

TEST	Step 1 – TD solenoid Ω	Step 4,5 -TCM output signal in “P” (engine off /ignition on)	Step 6 --TCM output signal in “D” (engine off /ignition on)
Location	B54 (#15-ground)	B54 - all conn plugged in (#15 -ground)	B54 - all conn plugged in (#15 -ground	AT Oil Temp Light Flashing?
Test Values FSM	10-17 Ω	< 1V	5V – 7V
Initial - Cold engine	12.6 Ω	0.139V	4.05V	NO
1st-Engine Hot & AT Oil Temp Flashing	24 Ω	11.83V	11.08V	YES
2nd-Engine Hot & AT Oil Temp Flashing	20+ Ω readings dropping	11.84	11.84	YES
Engine Hot – No AT Oil Temp Light	33	0.16	4.49	NO

NOTES:

• Torque bind occurs ONLY when AT Oil Temp Light Flashing
• Definitely temperature related – symptoms disappear as soon as engine allowed to cool down for as little as ~30 minutes. But come back quickly unless engine allowed to cool completely
• Shifting between gears seems a bit “hard” (with no light flashing / torque bind). This may normal for a Subaru (seems like I read that somewhere) but though it worth mentioning.
• OB does NOT have VDC

QUESTION:
I thought it interesting that whenever AT OIL TEMP light flashin, there is a direct correlation to high output V readings @ TCM. Is it possible the solenoid is going open circuit internally when hot (burned out) and needs replacing? What else could it be?

If any other readings or checks are desired, just say the word….I’ll jump right on it. Would taking readings with FWD fuse in be helpful?

[idosubaru]

You’re using the 6 cylinder FSM right? 4 and 6 cylinder are different

Any sign of transmission replacement?

Id check the rear diff ratio to make sure someone didn’t previously install a different rear diff. Rotate wheel and count ratio of rear diff input driveshaft revolutions to wheel revolutions to get ratio.  I think H6s are 4.11. 

I’m unsure how to differentiate those measurements, seems like they don’t rule anything out or confirm. 

A. The duty C is failing under load, temps, use. 

B. The wiring is heating up under load.  

C. The TCU is the culprit. 

It’s probably not the TCU but I’d probably swap the TCU first unless GD or someone else can point more specifically. TCU is plug and play and they’re dirt cheap and takes 10 minutes.  Use one from a 2001 or 2002 H6 nonVDC.  

I could possibly mail/sell you a TCU and refund your money when you ship it back if it’s not needed. 

Edited September 22, 2019 by idosubaru

[burtman]

Yes...I am using FSM for 6 cylinder, no VDC (same FSM...just different sections for 4 cyl, 6  cyl, w/VDC, w/o VDC, etc.)

No sign of transmission or differential replacement.  I’ll check ratio, but I am all but certain that differential and transmission are original.

I am sure that wiring harness is not issue, but I’ll do a few more checks when hot vs. cold to make sure.  Given the almost “mechanical” nature of the fault reaction to temperature, I am pretty convinced it lies within solenoid.  Sound reasonable?

I’d like to take you up on the “test” TCU.  I’ll PM you for how you’d like to work it out on payment, refund, etc.   I’m going out of town for a few days and will not be able to work on the OB.   So if we could work it out today or tomorrow that you could send it to me, I will test it out as soon as I return toward the end of next week. It certainly would be VERY convenient if it was the TCU, but it just seems unlikely to me given the nature of the fault. Is it common for TCU’s to fail?

Thank you...appreciate your help.  

[idosubaru]

No TCU failure isn’t common on Subarus. 

I’d guess solenoid too but guessing isn’t ideal?!

[Baddan]

I removed the drive shaft for now tell I order my clutch pack and solenoid it drives fine no more binding 

[Hellzbellz1234]

check the plugs on the transmission that come from the TCU and are near the exhaust. a heat shield might have been ripped off causing wire to melt. (am no expert just what i would take a look at)

[Rampage]

On 9/21/2019 at 3:07 PM, burtman said:

Initial - Cold engine

12.6 Ω 

0.139V

4.05V

NO

1st-Engine Hot & AT Oil Temp Flashing

24 Ω

11.83V

11.08V

YES

My first thought on the different resistance readings would be the crimp or solder connections (which ever they used) on the solenoid, where each end of the coil wire fasten to the terminals. They could be starting to break their connection. From there one goes to ground and the other goes to pin #15. Almost everything expands with heat.

Another thing that could happen (not very often) is the coil of the solenoid could have a few shorted turns. It will read very close to the correct ohms, but will draw more current than it should which may overload the transistor in the TCU that drives that solenoid causing it to overheat and pass less voltage than it should. Something I have run across working with electronics over the years.

In one of your posts you mentioned #16. You do know that pin is for the torque converter lockup solenoid.

[CNY_Dave]

would not be the first control or pickup coil winding that is good cold and bad hot!

 

The TCU monitors the voltages going to the solenoids, I have no idea what the 'good' window is but it evidently does not just look for 'dead short' or 'fully open'.

[burtman]

Thanks to all for the follow-up and suggestions...apologies for going Bueller.  Been busy as heck with work and this is my first chance to post.  I have checked and double-checked various ohm and voltage readings related to duty c solenoid and code 79.  I even supplied solenoid with 12V (when hot and AT Oil Temp light on)  to see if it activated solenoid - - No joy.  At this point, I tend to believe what Rampage suggested above...that that the solenoid has some internal issues that are triggered by heat. So I finally decided to go for it and replace the duty C solenoid and see what happens.  I ordered the parts and should have them in by early next week and installed by the end of the week.  Fingers crossed...

When I opened up the tranny extension case, found everything looks really good. There are some very slight “grooves” on the inside of the reduction drive gear from the clutch plates. Hardly noticeable...especially compared to what I have seen others have had to deal with. I suspect these are from the recent issues with the Duty C and AWD symptoms.

After looking at as many posts as I could find, I decided to go ahead an replace the clutch disks and various seals as well.  The parts I ordered include:

31523AA450    Plate Set Transfer Clutch
31337AA191    Gasket Trans Case Rear
31377AA211    Ring Seal (x2)
31940AA181    Sol Ay Transfer Valve (Duty C Solenoid)
805100030    Snap Ring (for clutch plates)
806735210    Oil Seal
44011AE040    Gasket-Exhaust Pipe Front (x2)
31325KA080    Bolt

Any tips, tricks, or suggestions on anything that might be helpful is much appreciated.  This is my first venture into a transmission, so I am borderline paranoid of going into FUBAR-land.  

One Q...I "found" a black rubber gasket (or grommet) loose in side transfer case cover when I removed it... ~1/2" diameter , black, round (I'll try to attach a pic to this post). What is this for and where does it go? I have looked at a number of diagrams and schematics and I am stumped.  Any ideas?

 

[Rampage]

About your picture. I just looked at one I have apart and I don't see any place for it. The ones used to mount the solenoid are taller with a groove around them.

[burtman]

I’m genuinely stumped.  I noticed the rubber gasket/grommet inside the cover immediately after taking it off. A mystery...what it is and how it got there?  
 

You mentioned something similar used to mount the solenoid?  I found it before unbolting the solenoid, so I doubt that is it anyway.  
 

Is there anything worse than having an “extra” part that you can’t figure out where it came from or where it goes?  Especially with something as complex as a transmission...Ugh

The only rational scenario I can come up with is that someone had opened up the case before and left it in there?  Not a good scenario any way you look at it...

[burtman]

Unfortunately, the needle bearing on the rear drive shaft (which extends into the xfer case cover) slipped out before I could pull it out.  So I will be on able to assure the needle bearing goes back in the same orientation as it was before.  It looks to be in very good condition.  Is it a critical issue if it does not go back in the same orientation as it came out? The bearing cost about $100. I’d rather not have to purchase a new one, but I will certainly do so if warranted.  The last thing I want is a bearing failure on the drive shaft.  
 

Thoughts?  Experience?

[Rampage]

No big deal with the needle bearings, just spray them with a cleaner and use a little Vaseline to hold them in place.

I have changed the differential and valve bodies in the 4EATs but I don't remember seeing that piece of rubber.