Kodiak Posted September 25, 2006 Report Share Posted September 25, 2006 Hi, first time post. Just bought my 1st Caddy with 89K, NICE CAR... but.... 1st good highway run and feeling that V8 power again... after which, the car began shifting hard. Now getting a P0748, (Pressure control solenoid circuit, electrical), computer checked by a local tranny shop. After reading through this forum... not too much on this problem.. Maybe PCM? Anyone with experience on this? best case-- worst case senerio? Also after reading through this forum, I'm hoping this isn't gonna be an albatross. I gave up GM 20 yrs ago and was hoping things were better. I never thought I'd have to pull an air cleaner assembly apart to check tranny fluid, while idling in park only to have the motor die from the extra fresh air..... geeeez.. I wanna like this car, really I do. Back to school for me.... Thanks for any response Link to comment Share on other sites More sharing options...
JimD Posted September 25, 2006 Report Share Posted September 25, 2006 My first step would be to check the condition of the wiring and the connector pins between the PCM and the transmission. At the connectors you will be looking for corrosion or bent pins. The PCM is located in the air intake plumbing up stream of the filter. On the left side of the engine about straight down from the master cylinder there is a round 20 pin connector that to the transmission. If you are experienced and comfortable using an Ohmeter, I can scan the schematic which gives pin-outs. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
Kodiak Posted September 26, 2006 Author Report Share Posted September 26, 2006 Thanks, I started at the PCM, found someone had been there before. The cellophane from a cigarette pack lying on top was a clue, but also noticed a wire splice at the rear-most connector, not sure which is feeding the tranny but, unscrewed it and all the it looks clean inside. Didn't pull the foward-most connector. Tried to follow the spliced wire and it ran out of the loom down between the engine and radiator to a small round connector. Lost it after that. With everything in place, started it up and no error messege so I ran through the gears and it was nice and smooth. Put everything back, closed the hood, started it up and .... same problem.... so this time I pulled the loom toward the engine to reroute, started it up and it runs great. Obviously a bad wire either at the connector or where the wires come out of the airbox. Now to figure out which wire! I really want to say thanks Jim, you saved me a bundle$$$$ 1stcaddy Link to comment Share on other sites More sharing options...
Astrak Posted September 26, 2006 Report Share Posted September 26, 2006 Worst case you will have to replace solenoid pack, best case you can drain some fluid and run seafoam through the transmission. But hopefully its just a faulty PCM. Link to comment Share on other sites More sharing options...
acklac7 Posted September 26, 2006 Report Share Posted September 26, 2006 I too have had intermittent pressure control solenoid issues ( I have OBD-I..so the code is PO76)...Typically the code pops up once every 6 months. Then goes to history on the next ignition cycle. Oddly enough I got the code like 6+ consecutive times about 5 months ago..Thought for sure that something had finally failed. But alas, it finally disappeared...and haven't heard from it since . All in all I guess what im trying to say is don't be surprised if P0748/P076 rears it's ugly little head again....In all likely hood it's a PCM issue I really want to say thanks Jim, you saved me a bundle$$$$ 1stcaddy And yeah....this forum will save you hundreds, if not thousands, of dollars A.J. Link to comment Share on other sites More sharing options...
Kodiak Posted September 26, 2006 Author Report Share Posted September 26, 2006 I know now the solenoid is good, I think the PCM is OK, seems to be in the wire harness or connector at the PCM. Moving it around makes the problem come and go. Link to comment Share on other sites More sharing options...
JimD Posted September 26, 2006 Report Share Posted September 26, 2006 .... Obviously a bad wire either at the connector or where the wires come out of the airbox. Now to figure out which wire! 1stcaddy Looks like you nailed it. The splice would bother me a lot. The wires to be concerned about from the PCM connector - one is red with black trace and the other is blue with white trace. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
Kodiak Posted September 26, 2006 Author Report Share Posted September 26, 2006 I'll look for them tomorrow. Happen to know whether it's the front or rear connector? It sure shifts smooth when its working, felt like I was shifting a manual without the clutch. OUCH! First good ride since the test drive! Link to comment Share on other sites More sharing options...
JimD Posted September 26, 2006 Report Share Posted September 26, 2006 Nope, can't tell front from rear on the schematic. What I can tell is you are looking for whichever one is C1, but I doubt the connectors are labeled. Wonder if someone hacked into the wiring to insert a switch so they could command high pressure shifts?? Find any evidence of unused wires anywhere in the cockpit? Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
Kodiak Posted September 26, 2006 Author Report Share Posted September 26, 2006 Wonder if someone hacked into the wiring to insert a switch so they could command high pressure shifts?? Find any evidence of unused wires anywhere in the cockpit? Yep there is, hangs out from under the glovebox in the footwell. Clipped right off. Strange little box mounted near there too. Looks like a tiny speaker in a plastic box. Thought maybe part of an alarm of some sort. I'll look into that to. I'll let you know the color of the wire that was spliced when I get back in there. Seem as if it were light blue with a white trace but I'll double check. It's a Canadian model. finding things like a block heater, 240mph (well, kph anyway) speedo. Many thanks, for all the help! Link to comment Share on other sites More sharing options...
Kodiak Posted September 27, 2006 Author Report Share Posted September 27, 2006 Still haven't had time to fix the wire to the PCM. I'll post when it's permanent. The clipped wire turned out to be part of an aftermarket handsfree system for a wireless phone..... Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.