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post #1 of 4 (permalink) Old 12-18-2017, 11:34 AM Thread Starter
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Automatic Transmission Goes to False Neutral

Hi all,

first I will describe the sequence of events of how the transmission problem emerged.
After that I will describe the findings obtained with the help of CRP123 scanner.

At the end of this year's very rainy summer, CHECK ENGINE light came on. The scanner showed that it was P0327 -
knock sensor. Since no knock was heard, I decided to replace knock sensor. Although Haynes repair manual says that it has to be done from below by first removing the starter, I found on youtube the video of how it can be done from above by removing intake manifold, which is much easier than removing starter from below.
So, I removed intake manifold and looked for the sensor above the starter. I noticed just one sensor and replaced it.
The code P0327 returned. I decided that it could be because of the harness of the sensor and decided to replace it too. To this end I had to remove insulation around the bundle of wires to which the wires of this harness belonged.
While removing the insulation, I noticed another, much smaller sensor near the sensor that I replaced. I searched on the internet for what else sensors are located right above the starter and found that there are 2 sensors: knock sensor and oil pressure sensor. It turned out that I replaced oil pressure sensor. So, I put the insulation around the bundle of wires back and replaced the knock sensor. The code P0327 disappeared. But next day while driving from work, I could not accelerate from a stop at a traffic light. RPMs were surging but the car was barely moving.
Since then the transmission behaves like this: it works fine when car is started in morning for about 15 mins of drive. Then RPMs start surging without any propulsion. I stop and idle for several minutes. After that transmission starts working normally again and problem does not return until next day.

The scanner shows that the problem begins when transmission fluid temperature is between 30 and 50 degrees of centigrade. When it is warned up enough, transmission behaves normally, as well as when it is cold.

Testing with the help of CRP123 scanner have shown that the difference between PC solenoid actual current and reference current is pretty high at times (about 0.5A). At these times the commanded gear could drop from 3 to 1 and then return back to 3 next second, as the difference does not last more than a second. All other times actual current and reference current are the same or differ by just about 0.02A.

No DTCs are thrown.

I checked the fluid level. It was okay. The fluid is red and does not smell burned.

Can somebody help with determining what causes the problem?

Thank everyone in advance.

Last edited by 2008CobaltOwner; 12-18-2017 at 11:37 AM.
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post #2 of 4 (permalink) Old 12-25-2017, 02:22 AM
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Could be the syncros.
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post #3 of 4 (permalink) Old 12-25-2017, 04:54 AM
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Automatic transmissions do not have synchros.

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post #4 of 4 (permalink) Old 12-25-2017, 06:14 AM
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Might be the filter
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