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Shift solenoid replacement 2005 G6 (P0758). Also might be applicable to P0753, P0973, P0974, P0976 and P0977.
Thought I should share my experience with replace Shift solenoid on a 2005 G6 Pontiac that was getting P0758 code and was defaulting to 2nd gear limp mode. Also the Traction Control off light was “on” from this issue.
First of all, this code could throw for other reasons. Search internet and there are suggestions on other reasons for the problem.
Here are a few good links to check out:
http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/automatic-transmission-shift-solenoid-tests-1
http://www.trutechtrans.com/Topic-1-00-01.html
http://www.justanswer.com/pontiac/3m7cp-transmission-won-t-shift-passed-2nd-gear-computer-issue.html
This transmission had been working fine (no slipping, etc).
Once the check engine light displayed, the car defaulted to 2nd gear when you put into drive and TC light was displayed.
After resetting the code (unhook battery for 15-30 mins OR reset with scanner), the car would start in 1st, then go to 2nd and then when it tried to go to 3rd, the check engine light and trac control off light would set and the car would default to 2nd.
I disconnected the electrical connection to the transmission (this diagram and chart is from http://www.justanswer.com/pontiac/3m7cp-transmission-won-t-shift-passed-2nd-gear-computer-issue.html). :
Pin Wire Color Circuit No. Function
A LT GRN 1222 1-2 Shift Solenoid Valve Control
B YEL/BLK 1223 2-3 Shift Solenoid Valve Control
C RED/BLK 1228 Pressure Control (PC) Solenoid Valve High Control
D LT BLU/WHT 1229 PC Solenoid Valve Low Control
E PNK 439 Ignition 1 Voltage
Checked pin E to make sure I had 12 volt of power. Used a test light and a small piece of wire that fit in the pin E. I could have followed this advice, but I didn’t : http://www.trutechtrans.com/Topic-1-00-01.html
I was pretty sure the 2-3 solenoid was bad from the P0758 code (and it was). To replace I did the following (I’m going off memory, but I think you will get the picture):
1. Removed air intake plenum.
2. Removed battery
3. Removed fuse box (there are 4 – 7mm bolts that are unscrewed and the connectors under the fuse box can be removed.
4. Removed PCM (silver module on side of fuse box tray).
5. Taped over connectors so no dirt got into them.
6. Removed battery/fuse box tray
7. Removed support for battery
8. Removed heater hose that was in the way (I might not have had to remove). Had tray to collect anti-freeze that came out.
9. Removed Transmission pan, drained fluid.
10. Removed shift linkage from top of transmission.
11. Unhooked any other wiring that was in the way.
12. Jacked up driver side of vehicle.
13. Removed front driver’s side tire.
14. Popped out the center cap.
15. Put tire back on and held with 2 lug nuts
16. Lowered vehicle.
17. Removed nut holding right side cv shaft to hub.
18. Jacked up vehicle and put jack stands on both sides.
19. Removed wheel
20. I took caliper off (hung on the spring with wire), the rotor and hub, but I don’t think I would have had too.
21. Took our bolt holding lower ball joint. Pryed out lower ball joint. (see youtube video for replacing CV shafts for more info).
22. Took pry bar and placed between CV shaft and transmission. Pryed off the CV shaft.
23. Used an engine hoist to hold motor.
24. Unhooked motor mounts. One on bottom by drivers side wheel well. One on front by where the electrical connection is to the transmission.
25. Unbolted all the bolts holding side transmission cover on. There are 2 or 3 bolts on the top that are different. Remember where these go when you reassemble.
26. **There is a plastic spacer inside the side cover where the CV shaft goes into transmission. Be careful to not drop and take note of how it’s positioned.
27. Tried to lift engine enough to allow side cover to be removed. ***I was unsuccessful with this!! However, I could get to the solenoids!!
28. Removed solenoids by carefully unhooking electrical connection with my fingernail and then a small pick to remove the big “u”clips holding the solenoids in (careful not to drop!!).
29. ** Careful when you unhook solenoids – they will pop out. Slowly remove and make sure nothing pops out of the hole the solenoid goes into. I read that one of them might have a valve under spring pressure that may pop out. Nothing popped out when I did this, but be warned…
30. The 2-3 solenoid had obvious plastic that had melted from shorting out. I also tested with multi-meter and registered 3 ohms compared to 26 on the new one. I went ahead and replaced both while I was in the transmission.

Other items:
I took pictures of everything prior to taking apart. I didn’t use, but had if necessary to know where things went. When putting the side cover back on, there is a plastic spacer inside the cover where the CV shaft goes in. Make sure to line this up correctly. The seal around the CV shaft was kind of ‘strange’ getting to go back in correctly. Take care to make sure it’s correct before tightening up side cover.
Hopefully this might help someone else. Ended up not being too bad and I might have gotten a bit lucky. I’m nervous as to why the solenoid went bad, but everything appears to be working correctly now.
 

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When you did this, why didn't you remove the transmission completely? Would there have been more to remove before it was completely out? How much space is available to access the solenoids while transmission is still roughly installed?
 
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