Need Shift solenoid help!!!!
08-28-2008, 02:46 PM
#1
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Need Shift solenoid help!!!! Hey Everyone.
I cant seem to figure this damn transmission out.
Heres the deal, im getting code "P0758" Which is shift solenoid circuit "B".
Well, i saw that, i immediately pulled the pan off & put 2 new solenoids in. Nothing changed.
However, through this whole thing, if the engine was cold, the trans would shift fine, untill it was warmed up, then it would code & i could only manually shift 2nd & 3rd gear.
Its got to the point now where it never shifts itself. Im stuck on this one. 2 brand new solenoids in it.
I read some information on another board about measuring resistance in the ecm connector, so i did.
2-3 Solenoid control wire (Pin 47 on '03+ ECM's) - No reading on resistance.
1-2 Solenoid Control wire (Pin 48) - No reading on resistance.
This has me pretty much stumped. Its a swapped transmission, but the transmission plug wasnt altered at all. What can be going on?
Ive checked all my fuses, their all good. Im not sure what else this can be?
Thanks!
Sheldon
I cant seem to figure this damn transmission out.
Heres the deal, im getting code "P0758" Which is shift solenoid circuit "B".
Well, i saw that, i immediately pulled the pan off & put 2 new solenoids in. Nothing changed.
However, through this whole thing, if the engine was cold, the trans would shift fine, untill it was warmed up, then it would code & i could only manually shift 2nd & 3rd gear.
Its got to the point now where it never shifts itself. Im stuck on this one. 2 brand new solenoids in it.
I read some information on another board about measuring resistance in the ecm connector, so i did.
2-3 Solenoid control wire (Pin 47 on '03+ ECM's) - No reading on resistance.
1-2 Solenoid Control wire (Pin 48) - No reading on resistance.
This has me pretty much stumped. Its a swapped transmission, but the transmission plug wasnt altered at all. What can be going on?
Ive checked all my fuses, their all good. Im not sure what else this can be?
Thanks!
Sheldon
08-28-2008, 02:52 PM
#2
When you are measuring the resistance are you measuring them to ground or to POS .
To make a resistance reading from the PCM to the solenoids you would need to 1 disconnect the battery. Then read from any 12v"if there was power" source and the wires you mentioned there you should see the resistance of the solenoid approx 22 ohms +-
The ignition switch would need to be in the on position during the test.
You see the solenoids with the switch on always have 12v applied and the PCM grounds the solenoids to turn them on
To make a resistance reading from the PCM to the solenoids you would need to 1 disconnect the battery. Then read from any 12v"if there was power" source and the wires you mentioned there you should see the resistance of the solenoid approx 22 ohms +-
The ignition switch would need to be in the on position during the test.
You see the solenoids with the switch on always have 12v applied and the PCM grounds the solenoids to turn them on
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08-31-2008, 08:30 AM
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Hey,
I didnt see your post before i went to the shop this morning, so i didnt check the wiring that way.
What i did was bridge the 1-2 and 2-3 wiring, then unplug the ecm connector, and use my meter thinger to check if there was a completele circuit between the 2. Turned out there was and that was fine.
I figured it must be a solenoid bad, so i pulled the pan off the transmission, and check resistance on both solenoids & both read 22. I decided id check if they were getting power (I know its the 2-3 that is my issue, but i figured id check both) and both have 12v power when the ignition is on.
What else can i check?
Im so confused by this. If my transmission connector was dirty, would it cause this issue? When i had the code coming up, if i cleared the code, it would shift fine for a few seconds, then when it coded again it would go back into fail safe.
Helpppp!!!! I need this car working for tuesday! Im crossing my fingers its a simple issue.
Sheldon
I didnt see your post before i went to the shop this morning, so i didnt check the wiring that way.
What i did was bridge the 1-2 and 2-3 wiring, then unplug the ecm connector, and use my meter thinger to check if there was a completele circuit between the 2. Turned out there was and that was fine.
I figured it must be a solenoid bad, so i pulled the pan off the transmission, and check resistance on both solenoids & both read 22. I decided id check if they were getting power (I know its the 2-3 that is my issue, but i figured id check both) and both have 12v power when the ignition is on.
What else can i check?
Im so confused by this. If my transmission connector was dirty, would it cause this issue? When i had the code coming up, if i cleared the code, it would shift fine for a few seconds, then when it coded again it would go back into fail safe.
Helpppp!!!! I need this car working for tuesday! Im crossing my fingers its a simple issue.
Sheldon
08-31-2008, 09:12 AM
#5
If you have replaced the solenoids and checked the wiring for the harness connector the next thing is to check for a complete circuit from the PCM to the trans at the PCM .
And there is also the possibility of a bad PCM
Do it the way I mentioned above
And there is also the possibility of a bad PCM
Do it the way I mentioned above
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Last edited by performabuilt; 08-31-2008 at 09:52 AM.
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09-01-2008, 05:04 PM
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im going to check all my wiring on it now, i really think its all good though, ill try deleteing the code & seeing if that makes a difference also.
Thanks!
Sheldon
Thanks!
Sheldon
09-02-2008, 02:53 PM
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Hey Everyone.
Checked all my wiring and solenoids and it turned out to all be good. I deleted the 2-3 code with HPTuners and it seems to be working A-OK now. Guess ill see how long this lasts but im hoping this is a fix.
Sheldon
Checked all my wiring and solenoids and it turned out to all be good. I deleted the 2-3 code with HPTuners and it seems to be working A-OK now. Guess ill see how long this lasts but im hoping this is a fix.
Sheldon
09-02-2008, 03:23 PM
#14
Well PO758 is a shift solenoid electrical fault , What this means is the PCM see either a short or and open in the electrical circuit for the solenoid either in the solenoid itself or in the wiring to the solenoid. Not like PO757 which is a code for the shift solenoid being stuck which may be a false code caused by the converter stall. Now it may be there nothing wrong with the electrical circuit or the solenoid ad the PCM has some issue causing it to think there is in which case turning the code off may solve the problem, I would say Wait and see and then go from there. Theres really no risk to trying it since all that could happen if there is a short is you blow the TCM fuse or if theres and open irractic operation .
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09-02-2008, 09:12 PM
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but frank, remember he is using a truck pcm which may throw different codes than say trans am's/camaro's let alone the different years and options. I do know for a fact that the trans tables/pressures are different for truck pcm's as well.
09-02-2008, 09:22 PM
#16
Yes but the solenoids in the trans are identical the PCM would have no idea what year trans it was hooked to. But as far as I can tell PO758 is always shift solenoid B electrical looking at ALL DATA and that huge all GM code list I put in our tech thread lol.
IMO if hes changed the solenoid and checked the wiring I would have to say the actual issue may be the PCM especially since the code set the code and it goes into limp just by starting the car with no movement. That sounds like it failed the mnute the solenoids were energized with the key on
IMO if hes changed the solenoid and checked the wiring I would have to say the actual issue may be the PCM especially since the code set the code and it goes into limp just by starting the car with no movement. That sounds like it failed the mnute the solenoids were energized with the key on
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09-02-2008, 09:34 PM
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Thanks for your help here!
Alright, so i deleted the code, im waiting to see how this turns out, in the mean time.
If i know my solenoid is good, i know my wiring is good, what can i be left to assume if the problem returns?
The PCM is a real expensive part to replace if its not going to cure my problem. All of this automatic stuff is stressing me out and making me want to convert to a 6spd, but im friggen poor.
The PCM controls all other aspects of the car perfectly. It shifts absolutaly fine, shifts up & down properly, perfect times etc, then suddenly it codes itself and goes into fail safe. Something is confusing me here, as why it would work perfectly then think it isnt working?
Any help is greatly appreciated. im hoping deleting the code works, but god knows if it will, and with my luck, it wont.
Not sure where else to go from here.
Sheldon
Alright, so i deleted the code, im waiting to see how this turns out, in the mean time.
If i know my solenoid is good, i know my wiring is good, what can i be left to assume if the problem returns?
The PCM is a real expensive part to replace if its not going to cure my problem. All of this automatic stuff is stressing me out and making me want to convert to a 6spd, but im friggen poor.
The PCM controls all other aspects of the car perfectly. It shifts absolutaly fine, shifts up & down properly, perfect times etc, then suddenly it codes itself and goes into fail safe. Something is confusing me here, as why it would work perfectly then think it isnt working?
Any help is greatly appreciated. im hoping deleting the code works, but god knows if it will, and with my luck, it wont.
Not sure where else to go from here.
Sheldon