Transmission started slipping after replacing oil pressure sensor

Transmission starts slipping when warms up to 30-50 degrees C but seems to be ok when fully warmed up.

Hello Scotty,

I recently replaced oil pressure sensor on my Pontiac G5 and next day transmission started slipping. I believe it is a coincidence.

So, I collected some data on transmission behavior using CPR123 scanner. When I start driving the car cold the transmission works perfect. If I go on highway, reach the speed of 100km/h and transmission locks, I probably can drive at that speed as long as I want. The funny things begin when I leave highway and stop at a traffic light. When I start moving RPMs skyrocket but there is no propulsion. If I stop and idle for some time, the power returns and transmission starts behaving normally. The scanner shows that acting up happens when transmission fluid temperature is between 30 and 50 degrees C. But when it is close to the normal operating temperature, then it seems to be ok. If when leaving the highway but just take a ramp, slowdown, then another ramp and go again to highway, it may start slipping at any speed. Here are the data from the scanner:

RPMs Calc. Throttle Position (%) Trans. Fluid Temp. (degree C) Commanded Gear My actions

===================================================================================================

1629 7.45 30 3 on the ramp to enter highway

2576 0 30 1 coasting along the ramp

2248 0 30 3

2157 0 30 2

1670 0 30 3

1593 0 30 3

1488 0 30 1

1244 0 30 3

982 0 30 3

1246 5.1 30 3 stepped a bit on gas

1649 7.45 30 3

1721 7.06 30 3

1478 0 30 3

1387 0 30 3

1248 0 31 3

1472 1.57 31 3 entered highway, started accelerating

1579 3.92 31 3

1728 5.1 31 3

1614 4.71 31 3

1608 5.49 31 3

1591 5.49 31 3

1583 5.49 31 3

1581 5.49 31 3

1608 6.27 31 3

1628 6.67 31 3

1801 8.63 31 3

1859 10.2 31 3

1876 11.37 31 3

1897 12.16 31 3

1892 12.94 31 3

1921 13.33 31 3

1930 14.12 31 3

1941 14.9 31 3

2001 16.47 31 3

2023 16.47 31 3

2149 19.22 31 4

1498 19.61 31 4

1514 19.61 31 4

1550 19.61 31 4

1593 19.61 31 4

1634 19.61 31 4

1664 19.61 31 4

1698 19.61 31 4

1732 19.61 31 4

1758 19.61 31 4

1794 19.61 31 4

1829 19.61 31 4

1862 19.22 32 4

1885 18.04 32 4

1904 17.65 32 4

1925 17.65 32 4

2332 16.86 32 4 RPMs starts fluctuating while maintaining

2130 15.69 32 4 the gas pedal position

2056 13.73 32 4

2020 13.73 32 4

2013 13.73 32 4

2001 13.73 32 4

1992 13.73 32 4

1998 14.51 32 4

2006 14.9 32 4

2017 14.9 32 4

2008 14.9 32 4

2415 14.9 32 4 RPMs fluctuate between 2200 and 2406

2324 14.9 32 4

2200 14.9 32 4

2345 14.9 32 4

2406 14.9 32 4

2301 14.51 32 2 RPMs start surging; The commanded gear

2521 10.2 32 2 drops to 2 but there is no propulsion; Calculated

2532 10.98 32 2 throttle position decreases as if it is in neutral

3021 10.98 32 2

3005 10.2 32 2 off gas pedal a bit to stop surging

2894 7.84 32 2

2930 7.84 32 2 on gas again: RMPs surge; Calculated throttle

3370 5.1 33 2 position is ridiculously low as compared to RPMs.

3544 7.06 33 2

3047 0 33 2 off gas pedal completely

2118 0 33 2

1442 1.18 33 2

2519 5.1 33 2 on gas again: RPMs surge

2511 0 33 2 off gas

1861 0 33 2

=========================================================================

I exited highway, idled for 5-10 minutes, transmission fluid temperature reached 60 degrees C, then I drove for an hour around the city with no problem. The surge has not returned.

The transmission is sealed for life and there is no leak. Still I tried to check the fluid level. I had to jack the front end a bit to reach the bolt. When I unscrewed it, the fluid poured from it. The car was not completely level though because of jacking. The fluid was red.

The car has just 126000 km on it. How to explain all these data and behavior and how to fix it?

Thank you in advance,

DIYer100001

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