PAezb Posted January 23, 2009 Share Posted January 23, 2009 OK, 96 OBW with 250K, auto tranny, recently got a P0748 - Pressure Solenoid A Electrical Failure. The symptoms caused by this are (1) a slightly harsher upshift from 1st to 2nd, and (2) No braking presser when manually downshifting from Drive to 3rd at highway speed - tach just drops down to idle. Other than that, she still shifts fine in all gears, and brakes in downshifting from 3rd to 2nd, and 2nd to 1st. Perfectly driveable but with the annoying CEL that returns eventually after clearing with OBDII scanner. Have done a tranny flush and added a half can of Seafoam TransTune. Have check all engine bay transmission connectors, disconnecting and clean with electrical cleaner,reconnected, and check and cleaned ground connections. No change. Connected Jason at Mike Scarff Subaru who did some quick research and says it could be 1 of 2 solenoids, one is $100, the other is $300, and estimated 3.5 hours labor. Could be the TCU as well. My ability to dig into this myself is limited as I dont have access to my tools or a place to work on the car. I'm handy with a VOM but have no reference on how to check the signals on the connectors in the bay or at the TCU. I'm a little reluctant to put a lot more money into her as I just finished a couple of months ago replacing the front axles, front wheel bearing, VSS, O2 sensor, accessory belts, coolant, hoses, thermostat. A service rep at local independent suggest just to drive her as is as long as it still shifts in all gears Suggestions or advice on what other diagnostics I can perform would be appreciated. Link to comment Share on other sites More sharing options...
nipper Posted January 23, 2009 Share Posted January 23, 2009 Let the shop dig into it a bit. All they need is an ohm meter and the car to find out whic solenoid has failed. Seems a shame to put all that money in the car and then give up. mechanics in my exp dont like to tell people to put money in a car with that many miles. nipper Link to comment Share on other sites More sharing options...
idosubaru Posted January 24, 2009 Share Posted January 24, 2009 someone with a dead trans might sell you a used solenoid for a few dollars? 3.5 hours to install doesn't sound bad for trans work, that means it's accessible from the transmission pan. don't normally say this but i'd consider keep driving it and see how it does. if it's completely failed and you don't mind driving it as is and are considering getting rid of it anyway..... Link to comment Share on other sites More sharing options...
mdjdc Posted January 24, 2009 Share Posted January 24, 2009 If you can find out which solenoid it isi I can dig into a dead tranny I have and get you one for cheap. Let me know what you want to do., Link to comment Share on other sites More sharing options...
PAezb Posted January 26, 2009 Author Share Posted January 26, 2009 (edited) Thanks for the feedback. I may check with a couple of local dealerships to see if they will at least ballpark the cost of diagnostics. Cant imagine it could be more than $100. In the meantime, it's driveable, and I suppose I could just leave it that way and run it until it, or other issue arise. It's been a good ride. 14 years, no rust but some dings and some front fender damage (my bad). Still has it original suspension (struts and springs) and exhaust - amazing! Uses oil but still gets 20 to 27 mpg - still fairly cheap to drive. Am hoping to make it to 300K before her retirement without putting a lot more cash into her, but that may be wishful thinking. Edited January 26, 2009 by PAezb Link to comment Share on other sites More sharing options...
nipper Posted January 26, 2009 Share Posted January 26, 2009 Thanks for the feedback. I may check with a couple of local dealerships to see if they will at least ballpark the cost of diagnostics. Cant imagine it could be more than $100. In the meantime, it's driveable, and I suppose I could just leave it that way and run it until it, or other issue arise. It's been a good ride. 14 years, no rust but some dings and some front fender damage (my bad). Still has it original suspension (struts and springs) and exhaust - amazing! Uses oil but still gets 20 to 27 mpg - still fairly cheap to drive. Am hoping to make it to 300K before her retirement without putting a lot more cash into her, but that may be wishful thinking. Are you willing to do a little diagnostics work yourself? Do you have an ohm meter? Link to comment Share on other sites More sharing options...
PAezb Posted January 26, 2009 Author Share Posted January 26, 2009 Yep, would like to do some diagnostics myself, but without some reference on what/where to test signals makes it more difficult, especially in cold weather (Minnesota). Thats what I was asking in my original post if anyone could provide some info or guidance. I do have an Ohm meter. Link to comment Share on other sites More sharing options...
nipper Posted January 26, 2009 Share Posted January 26, 2009 i think someone here will have pics of the connnectors here to show you. I can never get PDF files to post here . nipper Link to comment Share on other sites More sharing options...
OB99W Posted January 26, 2009 Share Posted January 26, 2009 I've attached a wiring diagram of the Duty Solenoid A circuit. If you disconnect the 16-pin connector B11 from T4, you can check the resistance of the solenoid between T4 pin 4 (ground) and pin 7. Expect to see about 3 ohms (the tolerance is about +/- an ohm). The part shown attached to B4 is the dropping resistor, which tempers how hard the shifts are. In addition to checking for open circuits, you should also check for shorts/leakage to ground. Link to comment Share on other sites More sharing options...
PAezb Posted January 27, 2009 Author Share Posted January 27, 2009 Thanks!, thats extremely helpful - I'll check it in the next couple of days as the weather is expected to warm up here. In the meantime, I just discovered another little issue, oil leak in the vincinity of what I believe is an oil pressure or temperture sensor (top front of the block, underneath the alternator, but above the cam position sensor - single wire with spade clip connector.) I've checked and tighten the sensor a bit, took to a local car was and used the degreaser spray to clean the engine off. A day later oil all over that sensor and small pools of it sitting under on the block :-\ :-\ So, I'm going to clean it off once again and watch it very carefully... God I just love the problems that come with old age.. Link to comment Share on other sites More sharing options...
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