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2005 Cadillac CTS 3.6L VVT
1,062 Posts
Discussion Starter · #1 ·
hi guys,

Like some of us here experiment some problem with the rpm boucing up and down when going downhill and coasting with the auto/transmission between 45mph and 55mph, I decided to put some cash on more diagnostics as possible.

I went at 3 different dealers and 2 independants transmission shops.

the 3 cadillac dealers checked for some dtc codes and nothing.. transmission is acting normal even though they see the rpm boucing. It only does the symptom when the a/c is running. without the a/c, everything is normal.

both independant shops scanned the car and did a road test. They checked how the transmission, throttle etc was working. They saw that the tcc was doing its job properly. When coasting or going downhill, they saw the load going down and tcc unlocking, locking, unlocking, locking... Air and gas mixture is still okay and everything is working normal but still the rpm needle is jumping. Both concluded that it was the load of the a/c on the engine/transmission that causes the bouncing rpm.

Now my concern is this: p1793 - Transmission Control Module Stack Overrun. no dealer found the code but the 2 independant transmission shop found it. Do you think it could be related?

What does p1793 means? I know it means Transmission Control Module Stack Overrun but what does it do?
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