Subaru Outback Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
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.
  • 1st 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 (Atlanta GA area) 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. 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.
 

·
Registered
Joined
·
16,403 Posts
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.
Done you're homework! That's good to see. Welcome to the forum!

Code 79 is:

"TROUBLE CODE 79 — TRANSFER DUTY SOLENOID — S004509E17
DIAGNOSIS:
"Output signal circuit of transfer duty solenoid is open or shorted." [underline added]

In other words, the problem isn't mechanical (in the transmission); it's electrical, somewhere in the connection to and through the solenoid.

It's not an uncommon fault code Often it's due to a broken connector at the solenoid, especially if the bottom of the transmission oil pan is, or ever was, dented (pushed up). The solenoid hangs down off the valve body, and the connector is only a fraction of an inch above the pan. Dent the pan, and the connector is pushed up and breaks.

Other possibilities include a defective solenoid coil, or a bad connection (open) between the TCM and the solenoid, perhaps in one of the harness connectors going to the transmission.

Definitely temperature related more than miles driven - AT Oil Temp light never flashes in cool weather or when driving through rain.
A bad contact in one of the connectors could be marginal, affected by temperature. If the connector at the solenoid has been damaged it could be loose, and the contact could vary with temperature. But this could also point to a faulty solenoid coil; I recall at least one earlier case where the coil inside the solenoid was going open circuit when the temperature was raised. Because the fault is temperature sensitive, it will be a challenge to narrow down, but if you get familiar with the transmission harness connectors, and can use a multimeter, then when the code is triggered, if the car is stopped and the connected separated, it might be possible to check the continuity through the solenoid while it's still hot.

I've attached the troubleshooting pages from the FSM.
 

Attachments

·
Registered
Joined
·
11 Posts
Discussion Starter #3
Plain OM---Thanks a bunch. I had already printed the TS pages from the FSM, but yours confirmed I am on the right track...Yay!

"Getting familiar with the transmission harness connectors" is proving to be a bit of a challenge, but I am making progress. That said, I have what is probably a "rookie" question...just not clear on the nomenclature used in the FSM - connector, terminal, etc.

Step 1 of the troubleshooting directs to measure resistance between trans connector and transmission terminals: "(T4) No. 6 - No. 16". I am not sure what this means as to where I should test resistance?
  • When I test resistance across #6 and # 16 on the B54 connector (unplugged from TCM), I read 26.6 ohms (engine cold) which is outside TS range of 10-17 ohms.
  • Alternatively, should I test resistance across #6 and #16 on T4 terminal (which I believe plugs into B11 connector on top of transmission)?
After testing resistance on B54 connector, I unplugged B11 connector (on top of transmission) and noticed that the male prong for #6 seemed to be missing (broken off?) on the opposite plug (is this T4?). Could this be my problem? If so, how best to fix? I could see sharpie marks on B11 connector and at the TCM, so obviously someone has been poking around with it before. I am thinking the "missing" prong may have been shaky before I opened it up.

The thought of trying to re-wire this 20-pole connector located deep inside the engine makes my skin crawl.😖 I don't even know if I could order a new one? Any advice on fixing this is much appreciated. I gotta believe someone has tackled this before...

Thanks again for your help...much appreciated.
 

·
Registered
Joined
·
16,403 Posts
Step 1 of the troubleshooting directs to measure resistance between trans connector and transmission terminals: "(T4) No. 6 - No. 16". I am not sure what this means as to where I should test resistance?
  • When I test resistance across #6 and # 16 on the B54 connector (unplugged from TCM), I read 26.6 ohms (engine cold) which is outside TS range of 10-17 ohms.
  • Alternatively, should I test resistance across #6 and #16 on T4 terminal (which I believe plugs into B11 connector on top of transmission)?
Step 1 is at connector T4, which is on the harness going down into the transmission. This is meant to first verify the continuity in that part of the wiring, i.e., the transmission harness and the transfer solenoid.

Although it's not shown in the troubleshooting page, pin 16 of connector T4 is ground. (See the A/T Control System schematics in the Wiring System section of the FSM.) At least initially, when testing for solenoid resistance and wiring continuity, you could measure from pin 6 of T4 to a good ground.

The same continuity through the solenoid could be checked at the TCM connector, as you did (therefore looking at all the wiring to the transfer solenoid), but the relevant pin number at B54 could be either 6 or 15, depending on whether or not the car has VDC. (According to the A/T Control System pages, when measuring between pins 6 and 16 of B54, you're actually measuring two different solenoids in series, which could well explain the 26 Ohms.) Moreover, although the ground wire from the transmission at T4 is pin 16, at connector B54, it's not pin 16 (reference the A/T Control System diagrams).

After testing resistance on B54 connector, I unplugged B11 connector (on top of transmission) and noticed that the male prong for #6 seemed to be missing (broken off?) on the opposite plug (is this T4?).
Yes, the connector that attaches to B11 should be T4, which, as noted, is on the transmission harness going down into the gearbox.

If pin 6 is missing, then that would certainly cause the code. (Also, when B11 and T4 are connected, and the resistance is measured at B54, there should be an open circuit.)

Sometimes the pin ends up being pushed back into the connector so check it closely, including at the wire on the back side of the connector. If the pin is there, it might be possible to just push it back (using the wire at the back) but then check that when the connectors are attached the pin hasn't again been pushed out. (If the pin is pushed back so that it is still making some contact at its tip with the other connector, that might explain the apparent temperature factor in triggering the code.)

Note: the connector diagrams (i.e., pin numbers/locations) at the bottom of the wiring diagram pages are looking at that connector at it's outside end (the side that the mating connector is attached), not the side where the wires go in.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #5
Thanks Plain OM…you are helping a lot…keeping me on the right track.

Let’s pretty much scratch everything in my last reply/post. It is actually #7 pin in T4 that is missing, and that slot isn’t used (no wire…DUH). After carefully studying the FSM A/T Control System schematic & digging a bit deeper into the harness setup, I walked through the troubleshooting diagnostics again:

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
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 let you know what I find.

Your advice and guidance is invited an appreciated...
 

·
Registered
Joined
·
16,403 Posts
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
The solenoid is driven by a duty cycle signal, i.e., a voltage (~10V) that is switched on and off rapidly. As such, a DC voltage measurement will depend not only on how long the voltage is "on" versus "off" (which varies depending on the degree to which the transfer clutch is being engaged), but also how the meter reacts to measuring this type of switching voltage (compared to a true DC voltage, which is normally constant). The 4.05 V could be a variance due to the meter response and small differences in the on versus off time (aka duty cycle %) at the time of the measurement.

As the fault apparently when the transmission is hot, getting some measurements at that time is probably the way to go before focusing on that one "failed" test.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #7
Thanks for the quick reply...you da man.(y)

I’ll get those resistance checks when hot and running as soon as I can and let you know what I find. Hopefully by tomorrow. But generally speaking, Is it fair to say that I am likely I headed towards a transfer duty solenoid replacement? What else could it be? Is this likely fixable without costing me big $s?

And would it be worthwhile to do another transmission fluid drain/refill with some BG ATC to see if it fixes it?

Just trying to manage my expectations here. I’d be interested in what your “gut” tells you.

Thanks again bud...if you were close I’d buy you a few cold ones.:)
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
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.

Thanks...
 

·
Registered
Joined
·
16,403 Posts
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)
Was the voltage measured with all the connectors attached, same way that tests5 and 6 were done for the previous reading above?

It's odd because the code had been set. When it is, according to the FSM, the TCM should de-energize the solenoid, i.e., apply no voltage. This causes the transfer valve to stay in its default position, which applies line pressure to the transfer clutch. That should lead to torque bind symptoms when making tight turns.

But the measurements are more than 12 V, which is close to system voltage. In a normally operating system, when the AWD fuse is installed, that sort of voltage is applied to the solenoid to cause full dis-engagement of the clutch. So 12 V with the code set doesn't seem right. Possible that the TCM output drive circuit is shorting, or there's a short in the harness somewhere to a wire carrying 12 V.

But first, perhaps double check those measurements.
 

·
Registered
Joined
·
16,403 Posts
BTW...I have checked to the best of my ability and I do NOT have VDC.
If it is VDC there should be a VDC Off switch on the dashboard. I believe it's to the left of the steering column. If there's no switch, then the car probably doesn't have it.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #11
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
QUESTIONS:

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?
 

·
Registered
Joined
·
16,403 Posts
Torque bind occurs ONLY when AT Oil Temp Light Flashing
Consistent with the FSM "failsafe" condition when the code is set, i.e. full application of the transfer clutch. (This is the default condition when the transfer solenoid is "off".)

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?
Seems to be, but doesn't necessarily eliminate the possibility of an intermittent continuity in the harness.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #13
No dents in the transmission pan at all. Looks pristine. But even if there was, my understanding is I will have to pull apart the back end of the tranny to get to it to fix or replace?

I’ve checked the harnesses thoroughly and they check out. The only exception being that last “lead” from T4 to the solenoid. I’ll try to take a look at it tomorrow to see if there is a pinch or kink in the lead. But assuming that checks out, what do you think we are looking at? Replace solenoid? Is it realistically worth another drain/refill with BG ATC added? I find it hard to believe that another drain/refill will “fix” the fault. But as you probably know by now, I am not so well versed on the electrical/controls side of things😩.

You’ve been a big help, so if your gut is telling you I should do something else, then I wanna hear it. I don’t mind re-checking my work.

And thanks for your prompt replies...👍
 

·
Registered
Joined
·
16,403 Posts
But even if there was, my understanding is I will have to pull apart the back end of the tranny to get to it to fix or replace?
Actually, that's right. In my reference to the pan, I was confusing your 2001 with another thread about a later year I'm working on. In your 2001, the transfer solenoid is indeed in the tail section, not on the valve body. (I've deleted the incorrect paragraph in my previous post.)
Is it realistically worth another drain/refill with BG ATC added?
Not in my view. As I see the code 79, it's an electrical problem, open or short circuit. The diagnostics leading to the code don't seem to relate to an intact but stuck solenoid valve (e.g., clogged with deposits), or something like that, which BG might help release.

If there were no fault in the system, 12V at the TCM terminal (B54/#15) should solidly turn on the solenoid which would, in turn, dis-engage the clutch, and there would be no torque bind symptoms when making tight turns. This is how the AWD disabling fuse works. When it's inserted, the TCM applies full voltage (perhaps a very high duty cycle) to the solenoid, causing the system to be in FWD mode. (Might want to confirm this when the system is cold and there's no fault. Where before there was 0.13 and ~4 V in P and D resp., with the fuse in, at least when in D and perhaps also P, I would think the voltage would be in the range of 10+ V.

Related background: Some have inserted a switch in the wire between the TCM and the solenoid. By turning the switch off (open), there's no voltage to the solenoid, and that causes the transfer clutch to be fully engaged, providing full AWD for particular driving applications. In doing this, of course, the TCM will detect an open circuit, so when the switch is set off, it also connects a resistor in place of the solenoid so that the TCM still "sees" the same load and doesn't detect a fault.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #15
Thanks bud. I’ll follow your suggestion and test the voltage with the fuse in (FWD) to see if there is 10+V on B54/#15. Assuming there is, am I correct that next step is to replace TD solenoid? Should that fix the problem?
 

·
Registered
Joined
·
16,403 Posts
Okay on checking the V with the fuse in and out, system cold. Let us know . . .

Should that fix the problem?
The only way to be sure it would fix the problem is to clearly isolate the fault. If the resistance measured at harness connector B54, pin 15, were very high, and that was also measured at T4, that would be a reasonable case. The recorded measurements aren't conclusive, given the range is 10-17 Ohms, and it measured (hot) 24 Ohms, but it's a good possibility. It could still be the wiring from T4 to the solenoid, but that also requires pulling the tail section to check.
 
1 - 16 of 16 Posts
Top