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2009 CTS-4, 2001 Seville STS
136 Posts
Discussion Starter · #1 · (Edited)
I was driving yesterday, and everything was 100% for the first hour.
Then I went into a customers place for an hour.
Came back out and started my car...
All of a sudden the "SERVICE TRANSMISSION" message is displayed on the dashboard.
When I moved the shifter from Park to Reverse then to Drive, a big BANG went through the car as the transmission shifted violently each time.
The engines RPM's were calm at around 700 or 800 I believe, and it runs smoothly.
Then I drove it home.... each shift through 1, 2, and 3 was very very rough.

When I got home, I checked the tranny fluid level, and its fine.
What could it be?

Oh, and here are the CURRENT codes I pulled...
There were lots of history ones, and I am under the impression that history ones arent important for current issues, so I left them out for now.

IPC U1000 - Class 2 Communication Malfunction
PCM P0036 - HO2S Heater Control Circuit Bank 1 Sensor 2
PCM P0410 - Secondary Air Injection (AIR) System
RSS C0579 - Left Front Solenoid Circuit Open
RSS C0615 - Left Front Position Sensor Malfunction
RSS C0620 - Right Front Position Sensor Malfunction

Thanks. :)

4,161 Posts
Chances are the system detected some fault (that's stored in history) and maxed its line pressure to protect the transmission. Max line pressure will cause hard shifting. Look at some history PCM codes to see if it has stored some transmission codes.
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