06 cobalt ls. 83k miles

Happened today while I was driving. Car wouldnt accelerate past 40mph. It shifts 1st to 2nd just fine. Once it hits 40, the rpms rise without any acceleration. Speedometer is working just fine. Check engine light came on with the following two codes: p0700, and p0757.

Someone told me to check and clean the 2 grounds on the transmission stud right behind radiator near radiator hose. The one ground was badly corroded, including the wire strands were green – this ground has multiple black wires with white stripes stripped and crimped to the terminal. I cleaned the strands and terminal best I could. After doing this, once I started the car, I got a 'power steering' notice and strange noise from the transmission. When I wiggled the wires to the terminal that was badly corroded, this noise and power steering light goes away. Perhaps I shorted/broke the wires while wiggling the terminal around trying to clean the terminal? Should I cut this terminal off and strip/recrimp wires to new terminal? The short appears to be right where the wires enter the terminal when wiggling.

What else should I look for? Fluid level? Electrical? Fuses/relays? The trans fluid and filter were changed at 55k. I didn't see any trans leaks under the car indicating a leak and possible low fluid level.

 

From what I have seen when the wire strands are green the wire is pretty well junk. If you have enough slack I would cut the wire back to the point where it is hopefully still preserved under the insulation and install a new terminal or build a new cable altogether. Alternatively you could source a good condition used or possibly new cable if they are available.

 

I did this today:

- I checked the trans fluid level by unscrewing the plug on the side and fluid poured out of check plug so I'm guessing fluid level is okay. Fluid was bright red. Last time I changed the fluid and filter was around 55k miles. I don't know if I want to gamble and spend the money on fluid and a filter just for it to do nothing.

- I ended up cutting the one terminal off that was corroded and stripped the wire back to nice shiny copper, then replaced with new terminal and coated with vaseline. This ground, has 5 black wires with white lines and they're crimped to a single terminal. Does anyone know if these wires ground multiple things or one?

- I also checked the wire harness near the oil filter housing as they say the heat from that can melt the wires and cause issues with transmission. I found no melted or broken wires here so I replaced sheathing and zip tied it all away from the oil filter housing.

After all this, I reconnected the battery, and drove. Once I hit 40mph and let off gas, and try to accelerate, the rpm's rise and nothing happens. I have to wait until it goes down around 30MPH and then accelerate and I can hit past 50, but I can hear the rpm's roaring from not going into 3rd gear. After 3 mins of driving the check engine light came back on and it was the same two codes: p0700 and p0757.

Is there any other diagnostic testing I can do without tearing into the transmission? Would fuses or relays cause these codes? Any electrical testing? I have a meter.

 

ended up being the shift soleoid. replaced solenoid and trans shift as good as new