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Old 10-30-2012, 12:19 PM   #1 (permalink)
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Default At oil temp light issue

I have 2002 outback automatic with the 2.5. 160,000k.

After driving about ten minutes the at oil temp light kicks on flashes until you restart the car. It then will go about another ten minutes before the same issue.

The car smells like the oil is getting hot when you park even though the flashing light is supposed to be an electrical issue. Could also be hot oil from leaky head gasket... Another story.

The car then throws a p0743 code which is a torque converter clutch solenoid electrical issue. it seems to do this directly after the at oil temp light starts flashing.

Also it threw a p0304, misfire on cylinder 4, code as well which may or may not be related. I changed plugs and I believe this problem is solved. It haven't been able to pull codes again.

I have flushed the transmission changed the at oil filter and searched this forum for the answer. No clear answers what it could be.

The car otherwise seems to have to major issues. Drives fine no binding or stalling and the lockout solenoid does seem to engage just fine.

What are the possible problems and is this something I can attack in a driveway? I was tempted to tear off the oil pan and check solenoids but wasn't sure how or what to check.

Any help would be awesome!

Thank you
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Old 10-30-2012, 01:15 PM   #2 (permalink)
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The car then throws a p0743 code which is a torque converter clutch solenoid electrical issue. it seems to do this directly after the at oil temp light starts flashing.
I guess that code is saying something.

That code is a generic OBD one that is in the standard alpha-numeric format. The transmission diagnostics system also has a separate set of 2 digit trouble codes. These can be read by some scanners, but there's a DIY method that gets the AT Oil Temp light to flash out the number. See: 199?-2004 How to Read AT Diagnostic Trouble Codes (DTCs) (Code 77 would be the same as the P0743.)

If the problem is electrical, such as a possible open or shorted connection to the torque converter lock-up clutch solenoid, then it might require some work to find the wiring and check for continuity or shorts section by section. But, sometimes it could just be a bad connection at the main transmission harness connector so it might be worth just disconnecting and reconnecting a few time to ensure there's good contact inside. (Follow the harness from the side of the transmission up over the bell housing -- I believe there should be one or two large connectors there.)

A wiring diagram for the AT's electrical system will be needed. (See attached.)
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File Type: pdf AT Control System.pdf (679.1 KB, 87 views)
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Old 10-30-2012, 09:15 PM   #3 (permalink)
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Also keep in mind that the AT Temp light acts like a MIL. When it flashes the TCM is trying to get your attention that something is going on that is not right and needs attention. Just like a MIL light flashing.

The 304 could have been caused by a reaction from whatever is going on inside the transmission. You could be at the start of a TCC solenoid failure or valve body issue that may result in the necessity to replace the torque converter and clean or replace the valve body with a complete system flush.

Just be aware that an issue may arise within the transmission. Try to pull any codes from the TCM and post them. Maybe its early enough on that a failure can be averted.
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Old 10-31-2012, 12:43 PM   #4 (permalink)
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Awesome grea advice. I will pull codes from tcm manually when I get home in a few days and also reconnect all harnesses on the transmission to check for faults or shorts. I will post any new codes or Information I find. Thank you!
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Old 11-12-2012, 08:53 PM   #5 (permalink)
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Alright so I have read the trouble codes directly from the TCM and it does read "77" which is the same as the PO743 issue apparently. Can i rule anything out because of this? Does this tell me that the wiring going to the computer is working properly? Should I still remove and check connections heading into transmission? I will do this when all the snow we have is gone.

Also I wanted to clarify if blinking at oil temp light is strictly an electrical issue or could the transmission actually be getting hot?


Thanks again for the help, very much appreciated!

J
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Old 11-12-2012, 10:08 PM   #6 (permalink)
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Check the ground cable at the transmission bell housing above the starter. Make sure the anchor is free of corrosion and tight.

I am trying to upload a screen shot of diagnostic flow to save typing. If I can get the file size corrected and make it readable, I'll post it.

Pretty much, there is a list of sensors to check which effect the TCC operation that can cause the "77".
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Old 11-12-2012, 10:34 PM   #7 (permalink)
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Try this again
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Old 11-12-2012, 10:36 PM   #8 (permalink)
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**** phone. Can anyone tell me why the **** thing puts the same file name on every upload?

Here's the other screen shot.
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Old 11-13-2012, 07:52 AM   #9 (permalink)
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Also I wanted to clarify if blinking at oil temp light is strictly an electrical issue or could the transmission actually be getting hot?
A blinking AT Oil Temp light is indicating a detected technical problem. If the ATF is overheating, the warning light normally would come on steady, not blinking. However, if there's both a technical problem and overheating, I don't know if one will take precedence over the other; that is, would the light flash to reflect the technical problem, or come on steady for the excessively hot ATF? (I suspect the former . . .)

Nevertheless, the code 77 is a technical problem, and according to the FSM, indicates that the electrical circuit between the TCM and the lock-up duty solenoid is either open or shorted. In this case the torque converter would, of course, not go into lock-up, and this, in turn, can cause the ATF to get excessively hot. (Most of the transmission heat is generated in the torque converter when the impeller and turbine are not turning at the same speed.)

First step might be to check the lock-up solenoid circuit for continuity. The wiring diagram was posted earlier. (I presume your car does not have VDC, in which case page WI-61 would be relevant.) You'll need to access the TCM connector (B54), and the main connector to the transmission wiring harness (B11/T4). No need to remove the pan etc at this stage.
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Old 11-13-2012, 06:58 PM   #10 (permalink)
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awesome great info! Thanks for the help. I will check the wiring first then maybe dig into testing the solenoids and connections. Thanks for all the great documents and advice!
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