PMBouquet Posted August 25, 2009 Share Posted August 25, 2009 Hi, I have read a couple of threads re: the P0743 code, which my 2002 Legacy Wagon has come back with. I am wondering if the mechanics (dealer) knows really what they are doing. They claim that P0743 is a code that should not be showing up on my 2002,that this code is applicable to 2004 and later models. Also, they are three hours (shop time, payable) of "diagnosis". And they say they need more time, so they kept my car and I had to rent a car for the evening. Could this be real? Symptoms I have noticed are, 1. the AT Temp light has been coming on intermittently for the last month or so. Took it to a different mechanic who said that there was no issue. We changed the fluid, and left it at that. Haven't seen the light for a few weeks. 2. I did notice (as was mentioned in another thread) the other day that the car stuck (briefly) in 3rd after a 1/2 mile hill climb. 3. The CEL came on. That's it. Car runs fine. It has 160k and new tires and brakes. Any advice? Thank you. Link to comment Share on other sites More sharing options...
OB99W Posted August 25, 2009 Share Posted August 25, 2009 P0743 is triggered when there's a problem with the lock-up duty solenoid circuit, and the TCM (Transmission Control Module) output is sensed to be incorrect. The symptom of that failure is lack of torque converter lock-up (after the engine is sufficiently warm). 2004 is not the first model year that code applies to. P0743 is an OBD-II code, but is the same as an AT (TCM) code 77, and diagnosis is done by following the procedure for code 77. The first step is to determine if there are any other OBD-II codes present besides the P0743. If so, they should be dealt with before concern over the P0743, since other things can cause the TCM to malfunction. If P0743 is the only code, then the cause is likely a bad connection or damaged wiring, bad lock-up solenoid, or faulty TCM. The procedure is to check for wiring problems external to the transmission and operation of the TCM before opening the trans and checking for internal electrical problems related to the solenoid. Using a basic volt/ohmmeter and a ''Select Monitor'' (which any Subaru dealer should have), following the code 77 diagnostic procedure, I don't see why so much time would be needed to determine what's wrong. Perhaps the technician who is working on your car is inexperienced. You might find the following an interesting read: http://www.subaruoutback.org/forums/showthread.php?postid=147743#post147743 Link to comment Share on other sites More sharing options...
PMBouquet Posted August 25, 2009 Author Share Posted August 25, 2009 Your info was of great assistance. Thank you. With your discussion as background, I discussed with them the basis for the code, etc. They reduced the overall charge to two hours, which I found acceptable. Pan was removed to expose wiring issue(s). They cleaned wiring and tested. Solenoid operates as it should. CEL off. I didn't pursue discussion with them re: their confusion, but will find another garage next time. Thank you! Link to comment Share on other sites More sharing options...
OB99W Posted August 25, 2009 Share Posted August 25, 2009 You're welcome. Let's hope that it's resolved long-term. Although in your case the problem apparently was internal to the transmission, this sort of trouble is often caused by external wiring/connection problems, since there's more exposure to the elements and things that can cause physical damage. Link to comment Share on other sites More sharing options...
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