Check Engine Light With Code P1870 on Chevrolet Silverado 1500

Vehicles equipped whit a 4 speed automatic transmission may develop a harsh 1-2 shift and/or illumination of the Check Engine Light with code P1870 stored. This can be caused by wear of the bore for the TCC isolator and regulator valves in the valve body. This condition does not commonly occur until the transmission reaches normal operating temperature. If the valve body is worn, replacement will be necessary to correct this concern.

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Average mileage: 117,000 (50,000–160,000)
Drive Trains affected: 4WD, Automatic Transmission
3 model years affected: 1999, 2000, 2008
8 people reported this problem
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problem details
2000 Chevrolet Silverado 1500 - Automatic Transmission 160,000 mi,
With the a/c on and the cruise control engaged on a hot day I get the hard 1,2 shifts with the p1870 code.
code 1870 train. slips 1st. to 2nd. not all the time